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Sample records for crystalline ceramic layers

  1. Biomimetic processing of oriented crystalline ceramic layers

    Energy Technology Data Exchange (ETDEWEB)

    Cesarano, J.; Shelnutt, J.A.

    1997-10-01

    The aim of this project was to develop the capabilities for Sandia to fabricate self assembled Langmuir-Blodgett (LB) films of various materials and to exploit their two-dimensional crystalline structure to promote the growth of oriented thin films of inorganic materials at room temperature. This includes the design and synthesis of Langmuir-active (amphiphilic) organic molecules with end groups offering high nucleation potential for various ceramics. A longer range goal is that of understanding the underlying principles, making it feasible to use the techniques presented in this report to fabricate unique oriented films of various materials for electronic, sensor, and membrane applications. Therefore, whenever possible, work completed in this report was completed with the intention of addressing the fundamental phenomena underlying the growth of crystalline, inorganic films on template layers of highly organized organic molecules. This problem was inspired by biological processes, which often produce exquisitely engineered structures via templated growth on polymeric layers. Seashells, for example, exhibit great toughness owing to their fine brick-and-mortar structure that results from templated growth of calcium carbonate on top of layers of ordered organic proteins. A key goal in this work, therefore, is to demonstrate a positive correlation between the order and orientation of the template layer and that of the crystalline ceramic material grown upon it. The work completed was comprised of several parallel efforts that encompassed the entire spectrum of biomimetic growth from solution. Studies were completed on seashells and the mechanisms of growth for calcium carbonate. Studies were completed on the characterization of LB films and the capability developed for the in-house fabrication of these films. Standard films of fatty acids were studied as well as novel polypeptides and porphyrins that were synthesized.

  2. Synthesis of Micro/Nano Crystalline Ceramics

    Science.gov (United States)

    Mathew, Philip; Isac, Sheelakumari; Abraham, Rosalin; Isac, Jayakumari

    2008-04-01

    As a matter of fact almost every industrial production line, office and home is dependant on ceramic materials. Newly designed devices incorporate ceramic materials because of their useful chemical, electrical, mechanical, thermal and structural properties. The effectiveness of a large system depends critically on its ceramic components. That is ceramics are important, first because they comprise a large basic industry and second because their properties are essential for many applications. Ceramics are more stable than metals both in chemical and thermal environments. In this work the authors describes a method for the preparation of PBT ceramics material from lead oxide (PbO), barium carbonate and titanium oxide based on pre-calcinations of oxides. The results were analyzed by X-ray Diffraction (XRD), Infrared Spectroscopy (IR) and TGA. XRD and SEM studies revealed that its particle size is in nanometer range. Dielectric studies were conducted at a frequency range of 100 KHz to 13 MHz. Mechanical properties were calculated.

  3. Evaluation of Respirable Crystalline Silica in High School Ceramics Classrooms

    Directory of Open Access Journals (Sweden)

    Matthew Fechser

    2014-01-01

    Full Text Available Air concentrations of respirable crystalline silica were measured in eleven (11 high school ceramics classrooms located in Salt Lake County, UT, USA. Respirable dust was collected on PVC filters using precision flow pumps and cyclone samplers (n = 44. Filters were subsequently analyzed for respirable dust and percent crystalline silica content. The geometric mean of the silica concentrations was 0.009 mg/m3 near the teacher’s work station and 0.008 mg/m3 near the kilns. The number of students in the classroom was correlated to the silica concentration in the ceramics classroom, but no correlation was found between the silica concentrations and either the size of the classroom or the age of the building. Results from this study indicate that ceramics teachers may be at an increased risk of exposure to crystalline silica based on the ACGIH TLV of 0.025 mg/m3, with an exceedance of 21%.

  4. Evaluation of respirable crystalline silica in high school ceramics classrooms.

    Science.gov (United States)

    Fechser, Matthew; Alaves, Victor; Larson, Rodney; Sleeth, Darrah

    2014-01-23

    Air concentrations of respirable crystalline silica were measured in eleven (11) high school ceramics classrooms located in Salt Lake County, UT, USA. Respirable dust was collected on PVC filters using precision flow pumps and cyclone samplers (n = 44). Filters were subsequently analyzed for respirable dust and percent crystalline silica content. The geometric mean of the silica concentrations was 0.009 mg/m3 near the teacher's work station and 0.008 mg/m3 near the kilns. The number of students in the classroom was correlated to the silica concentration in the ceramics classroom, but no correlation was found between the silica concentrations and either the size of the classroom or the age of the building. Results from this study indicate that ceramics teachers may be at an increased risk of exposure to crystalline silica based on the ACGIH TLV of 0.025 mg/m3, with an excess of 21%.

  5. Evaluation of Respirable Crystalline Silica in High School Ceramics Classrooms

    OpenAIRE

    Matthew Fechser; Victor Alaves; Rodney Larson; Darrah Sleeth

    2014-01-01

    Air concentrations of respirable crystalline silica were measured in eleven (11) high school ceramics classrooms located in Salt Lake County, UT, USA. Respirable dust was collected on PVC filters using precision flow pumps and cyclone samplers (n = 44). Filters were subsequently analyzed for respirable dust and percent crystalline silica content. The geometric mean of the silica concentrations was 0.009 mg/m3 near the teacher’s work station and 0.008 mg/m3 near the kilns. The number of studen...

  6. Crystalline ceramics: Waste forms for the disposal of weapons plutonium

    Energy Technology Data Exchange (ETDEWEB)

    Ewing, R.C.; Lutze, W. [New Mexico Univ., Albuquerque, NM (United States); Weber, W.J. [Pacific Northwest Lab., Richland, WA (United States)

    1995-05-01

    At present, there are three seriously considered options for the disposition of excess weapons plutonium: (i) incorporation, partial burn-up and direct disposal of MOX-fuel; (ii) vitrification with defense waste and disposal as glass ``logs``; (iii) deep borehole disposal (National Academy of Sciences Report, 1994). The first two options provide a safeguard due to the high activity of fission products in the irradiated fuel and the defense waste. The latter option has only been examined in a preliminary manner, and the exact form of the plutonium has not been identified. In this paper, we review the potential for the immobilization of plutonium in highly durable crystalline ceramics apatite, pyrochlore, monazite and zircon. Based on available data, we propose zircon as the preferred crystalline ceramic for the permanent disposition of excess weapons plutonium.

  7. Stable liquid crystalline phases of colloidally dispersed exfoliated layered niobates.

    Science.gov (United States)

    Nakato, Teruyuki; Miyamoto, Nobuyoshi; Harada, Akiko

    2004-01-07

    Colloidally dispersed niobium oxide nanosheets obtained by exfoliation of layered niobates HNb(3)O(8) and HTiNbO(5) formed stable liquid crystalline phases; their liquid crystallinity was dependent on the niobate species exfoliated.

  8. Ceramic nanostructure materials, membranes and composite layers

    NARCIS (Netherlands)

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

    1989-01-01

    Synthesis methods to obtain nanoscale materials will be briefly discussed with a focus on sol-gel methods. Three types of nanoscale composites (powders, membranes and ion implanted layers) will be discussed and exemplified with recent original research results. Ceramic membranes with a thickness of

  9. Three-dimensionally layered ceramic blocks.

    Science.gov (United States)

    Kurbad, Andreas

    2010-01-01

    With the aid of an innovatively structured ceramic block, it is possible to achieve results at a high esthetic level with relatively simple means. In the three-dimensionally structured Vitablocs RealLife, translucent enamel ceramic is arranged around a conically structured, opaque dentin core. The virtual restoration can be positioned freely in all three dimensions with the aid of the Cerec/inLab software. The restorations are milled fully anatomically and only minimally glazed or characterized with stains. Results that otherwise can be achieved only with much more complex layering processes are possible.

  10. Joining Dental Ceramic Layers With Glass

    Science.gov (United States)

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

    2011-01-01

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

  11. Effects of porosity and crystallinity of glass ceramics on the in vivo bioactive response

    Energy Technology Data Exchange (ETDEWEB)

    Xin Renlong [School of Materials Science and Engineering, Chongqing University, Chongqing (China); Zhang Qiyi; Leng Yang [Department of Mechanical Engineering, Hong Kong University of Science and Technology, Hong Kong (China); Chen Jiyong [Engineering Research Center in Biomaterials, Sichuan University, Chengdu (China)], E-mail: rlxin@cqu.edu.cn

    2008-12-15

    Two types of glass ceramics with different porosities and crystallinities were produced by sintering 45S5 Bioglass (registered) particulates. The in vivo bioactive response of the glass ceramics was evaluated by implanting them in rabbit muscle sites. After six weeks implantation, silicon-rich networks were observed on both types of ceramics, but the number of networks was much larger in the poorly crystallized dense ceramics than in the well crystallized porous ones. This indicated that the crystallization of glass ceramics retarded the formation of networks on surfaces. Apatite precipitation was found in pore areas of the porous ceramics, but not on the dense ones, suggesting that porosity was necessary for glass ceramics to induce apatite precipitation in a rabbit model. (communication)

  12. Basic research in crystalline and noncrystalline ceramic systems. Annual report

    Energy Technology Data Exchange (ETDEWEB)

    Kingery, W. D.; Coble, R. L.

    1968-04-01

    Various research subjects on ceramics have been investigated, including heat conduction, surface characteristics, diffusion in oxides, high-temperature kinetic processes, microstructure development, effects of microstructure on properties, structure and properties of noncrystalline ceramics, dissolution kinetics, and solid-vapor reactions. (DLC)

  13. A method for the densification of ceramic layers, especially ceramic layers within solid oxide cell (SOC) technology, and products obtained by the method

    DEFF Research Database (Denmark)

    2013-01-01

    A ceramic layer, especially for use in solid oxide cell (SOC) technology, is densified in a method comprising (a) providing a multilayer system by depositing the porous ceramic layer, which is to be densified, onto the selected system of ceramic layers on a support, (b) pre-sintering the resulting...

  14. The effects of sulfate content on crystalline phase, microstructure, and chemical durability of zirconolite-barium borosilicate glass-ceramics

    Science.gov (United States)

    Wu, Lang; Wang, Xin; Li, Huidong; Teng, Yuancheng; Peng, Long

    2016-09-01

    The effects of sulfate content on structure and chemical durability of barium borosilicate glass-ceramics were studied. The results show that the glass-ceramics with 0-1.10 mol% SO3 possess mainly CaZrTi2O7-2M phase along with a small amount of CaZrTi2O7-3T and ZrO2 phases. The hexagonal CaZrTi2O7-3T crystals crystallize on the surface of glass-ceramics. For the samples with 1.24-1.55 mol% SO3, the main crystalline phases are CaTiSiO5 and CaZrTi2O7-2M in the bulk, while a separate sulfate layer containing Na2SO4 and BaSO4 is observed on the surface. X-ray fluorescence analysis indicates that about 2/3 of the SO3 originally added has been lost by volatility. The normalized mass loss (NLi) for Na, B, Ca elements remains almost unchanged (∼10-2 g/m2) after 7 days for the samples with 0-1.10 mol% SO3. The NLi for both Na and B increases gradually after 7 days when the SO3 content is 1.24 mol%.

  15. The influence of glass composition on crystalline phase stability in glass-ceramic wasteforms

    Science.gov (United States)

    Maddrell, Ewan; Thornber, Stephanie; Hyatt, Neil C.

    2015-01-01

    Zirconolite glass-ceramic wasteforms were prepared using a suite of Na2O-Al2O3-B2O3-SiO2 glass matrices with variable Al:B ratios. Zirconolite was the dominant crystalline phase only for the most alumina rich glass compositions. As the Al:B ratio decreased zirconolite was replaced by sphene, zircon and rutile. Thermodynamic data were used to calculate a silica activity in the glass melt below which zirconolite is the favoured crystalline phase. The concept of the crystalline reference state of glass melts is then utilised to provide a physical basis for why silica activity varies with the Al:B ratio.

  16. Perforated layer structures in liquid crystalline block copolymers

    Science.gov (United States)

    Tenneti, Kishore; Chen, Xiaofang; Li, Christopher; Tu, Yingfeng; Wan, Xinhua; Zhou, Qi-Feng; Sics, Igors; Hsiao, Benjamin

    2006-03-01

    Phase structures of a series of poly(styrene-block-(2,5-bis-(4- methoxyphenyl)oxycarbonyl)styrene) (PS-b-PMPCS) liquid crystalline “rod-coil” block copolymers (LCBCPs) were investigated using thermal analysis, X-ray analysis and transmission electron microscopy. In the low molecular weight asymmetric BCP system, perforated layer structures were observed where the excessive PS molecules punctured the PMPCS domains and these perforations uniquely possess tetragonal in- plane symmetry. In the high molecular weight system, these perforated layer structures were observed in symmetric samples. Randomly initiated perforations became more regular and uniform upon blending with PS homopolymer in symmetric BCPs. These regular perforations also possess tetragonal in-plane symmetry.

  17. Damage maps for layered ceramics under simulated mastication.

    Science.gov (United States)

    Kim, J-H; Kim, J-W; Myoung, S-W; Pines, M; Zhang, Y

    2008-07-01

    Ceramic restorations, whether monolithic (single layer) or porcelain-veneered, often chip and fracture from repeated occlusal loading. Occlusion involves the opposing tooth sliding along the cuspal incline surface with an applied biting force (off-axis loading). We hypothesized that off-axis contact-load-slide-liftoff fatigue, as compared with normal axial fatigue loading, produces different fracture modes and fatigue lifespans of layered ceramics. Monolithic glass plates were epoxy-bonded to polycarbonate substrates as a transparent model for an all-ceramic crown on dentin. Off-axis and axial (control) cyclic loading was applied through a hard sphere in water, with a mouth-motion machine. The off-axis loading is more deleterious for contact-induced occlusal surface fracture, but less harmful for flexure-induced cementation surface fracture of brittle layers than the axial loading. This is because of the tangential load component associated with the off-axis loading. Clinical relevance is discussed.

  18. Flexural strength and failure modes of layered ceramic structures

    Science.gov (United States)

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

    2011-01-01

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

  19. DEVELOPMENT OF CRYSTALLINE CERAMICS FOR IMMOBILIZATION OF ADVANCED FUEL CYCLE REPROCESSING WASTES

    Energy Technology Data Exchange (ETDEWEB)

    Fox, K.; Brinkman, K.

    2011-09-22

    The Savannah River National Laboratory (SRNL) is developing crystalline ceramic waste forms to incorporate CS/LN/TM high Mo waste streams consisting of perovskite, hollandite, pyrochlore, zirconolite, and powellite phase assemblages. Simple raw materials, including Al{sub 2}O{sub 3}, CaO, and TiO{sub 2} were combined with simulated waste components to produce multiphase crystalline ceramics. Fiscal Year 2011 (FY11) activities included (i) expanding the compositional range by varying waste loading and fabrication of compositions rich in TiO{sub 2}, (ii) exploring the processing parameters of ceramics produced by the melt and crystallize process, (iii) synthesis and characterization of select individual phases of powellite and hollandite that are the target hosts for radionuclides of Mo, Cs, and Rb, and (iv) evaluating the durability and radiation stability of single and multi-phase ceramic waste forms. Two fabrication methods, including melting and crystallizing, and pressing and sintering, were used with the intent of studying phase evolution under various sintering conditions. An analysis of the XRD and SEM/EDS results indicates that the targeted crystalline phases of the FY11 compositions consisting of pyrochlore, perovskite, hollandite, zirconolite, and powellite were formed by both press and sinter and melt and crystallize processing methods. An evaluation of crystalline phase formation versus melt processing conditions revealed that hollandite, perovskite, zirconolite, and residual TiO{sub 2} phases formed regardless of cooling rate, demonstrating the robust nature of this process for crystalline phase development. The multiphase ceramic composition CSLNTM-06 demonstrated good resistance to proton beam irradiation. Electron irradiation studies on the single phase CaMoO{sub 4} (a component of the multiphase waste form) suggested that this material exhibits stability to 1000 years at anticipated self-irradiation doses (2 x 10{sup 10}-2 x 10{sup 11} Gy), but that

  20. Injection molding of ceramic filled polypropylene: The effect of thermal conductivity and cooling rate on crystallinity

    Energy Technology Data Exchange (ETDEWEB)

    Suplicz, A.; Szabo, F.; Kovacs, J.G., E-mail: kovacs@pt.bme.hu

    2013-12-20

    Highlights: • BN, talc and TiO{sub 2} in 30 vol% were compounded with polypropylene matrix. • According to the DSC measurements, the fillers are good nucleating agents. • The thermal conductivity of the fillers influences the cooling rate of the melt. • The higher the cooling rate is, the lower the crystallinity in the polymer matrix. - Abstract: Three different nano- and micro-sized ceramic powders (boron-nitride (BN), talc and titanium-dioxide (TiO{sub 2})) in 30 vol% have been compounded with a polypropylene (PP) matrix. Scanning electron microscopy (SEM) shows that the particles are dispersed smoothly in the matrix and larger aggregates cannot be discovered. The cooling gradients and the cooling rate in the injection-molded samples were estimated with numerical simulations and finite element analysis software. It was proved with differential scanning calorimetry (DSC) measurements that the cooling rate has significant influence on the crystallinity of the compounds. At a low cooling rate BN works as a nucleating agent so the crystallinity of the compound is higher than that of unfilled PP. On the other hand, at a high cooling rate, the crystallinity of the compound is lower than that of unfilled PP because of its higher thermal conductivity. The higher the thermal conductivity is, the higher the real cooling rate in the material, which influences the crystallization kinetics significantly.

  1. Crystalline SiCO: Implication on structure and thermochemistry of ternary silicon oxycarbide ceramics

    Science.gov (United States)

    Bodiford, Nelli

    The need for innovative refractory materials---materials that can sustain extreme temperatures---has been constantly growing within the modern industries. Basic requirements for usage at ultra-high-temperatures have been considered such as high melting point, high structural strength, exceptional resistance to oxidation, zero or almost zero creep. Monolithic ceramics alone cannot provide these properties, therefore, composite materials are sought to fulfill the demand. For example, silicon nitride and silicon carbide based ceramics have long been leading contenders for structural use in gas turbine engines. In the course of this work we are investigating amorphous SiCO formed via polymer-to-ceramic route. Previously a considerable amount of work has been done on structures of stoichiometric amorphous SiCO and a "perfect" random network was obtained (experimentally as well as supported by computational work) up to the phase content of 33 mol-% SiC. By "perfect" one assumes to have four fold coordinated Si atoms bonded to C and O; C atoms bond to Si atoms only and O is two fold connected to Si. Beyond 33 mol-% SiC within SiCO phase the structural imperfections and defects start to develop. Aside from the stoichiometric form of SiCO, the polymer-to-ceramic route allows for the incorporation of high molar amounts of carbon to create SiCO ceramic with excess carbon. The incorporation of carbon into silica glass improves high-temperature mechanical properties and increases resistance to crystallization of the amorphous material. The amount of 'free carbon' can be controlled through the choice of precursors used during synthesis. There were no ternary crystalline phases of SiCO observed. However, in systems such as MgO-SiO2, Na2O-Al2O 3-SiO2 there are ternary crystalline compounds (MgSiO 3, Mg2SiO4, NaAlSiO4, NaAlSi3 O8) that are of a greater energetic stability than glasses of the same composition. What makes the SiCO system different? In the approach proposed in this

  2. A randomized controlled clinical trial of 3-unit posterior zirconia–ceramic fixed dental prostheses (FDP) with layered or pressed veneering ceramics: 3-year results

    OpenAIRE

    Naenni, Nadja; Bindl, Andreas; Sax, Caroline; Hämmerle, Christoph; Sailer, Irena

    2015-01-01

    The aim of the present pilot study was to test whether or not posterior zirconia-ceramic fixed dental prostheses (FDPs) with pressed veneering ceramic exhibit less chipping than FDPs with layered veneering ceramics

  3. Effect of various intermediate ceramic layers on the interfacial stability of zirconia core and veneering ceramics.

    Science.gov (United States)

    Yoon, Hyung-In; Yeo, In-Sung; Yi, Yang-Jin; Kim, Sung-Hun; Lee, Jai-Bong; Han, Jung-Suk

    2015-01-01

    The purposes of this study were to evaluate the effects of intermediate ceramics on the adhesion between the zirconia core and veneer ceramics. The polished surfaces of fully sintered Y-TZP blocks received three different treatments: (1) connector (C), (2) liner (L) or (3) wash layer (W). All the treated zirconia blocks were veneered with either (a) fluorapatite glass-ceramic (E) or (b) feldspathic porcelain (V) and divided into four groups (CE, CV, LE and WV). For the control group, the testing surfaces of metal blocks were veneered with feldspathic porcelain (VM). A half of the samples in each group (n = 21) were exposed to thermocycling, while the other half of the specimens were stored at room temperature under dry conditions. All specimens were subjected to the shear test and the failed surfaces were microscopically examined. The elemental distribution at the zirconia core/veneer interface was analyzed. The specimens in Groups CE and CV exhibited significantly greater mean bond strength values than those in Groups LE and WV, respectively (p core/veneer adhesion than the other intermediate ceramics evaluated in the study. However, thermal cycling affected the bond strength at the core/veneer interface differently according to the intermediate ceramics.

  4. Improved performance of diatomite-based dental nanocomposite ceramics using layer-by-layer assembly

    Science.gov (United States)

    Lu, Xiaoli; Xia, Yang; Liu, Mei; Qian, Yunzhu; Zhou, Xuefeng; Gu, Ning; Zhang, Feimin

    2012-01-01

    To fabricate high-strength diatomite-based ceramics for dental applications, the layer-by-layer technique was used to coat diatomite particles with cationic [poly(allylamine hydrochloride)] and anionic [poly(sodium 4-styrenesulfonate)] polymers to improve the dispersion and adsorption of positively charged nano-ZrO2 (zirconia) as a reinforcing agent. The modified diatomite particles had reduced particle size, narrower size distribution, and were well dispersed, with good adsorption of nano-ZrO2. To determine the optimum addition levels for nano-ZrO2, ceramics containing 0, 20, 25, 30, and 35 wt% nano-ZrO2 were sintered and characterized by the three-point bending test and microhardness test. In addition to scanning electron microscopy, propagation phase-contrast synchrotron X-ray microtomography was used to examine the internal structure of the ceramics. The addition of 30 wt% nano-ZrO2 resulted in the highest flexural strength and fracture toughness with reduced porosity. Shear bond strength between the core and veneer of our diatomite ceramics and the most widely used dental ceramics were compared; the shear bond strength value for the diatomite-based ceramics was found to be significantly higher than for other groups (P dental materials. PMID:22619551

  5. The effects of sulfate content on crystalline phase, microstructure, and chemical durability of zirconolite−barium borosilicate glass-ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Lang, E-mail: lang.wu@163.com [State Key Laboratory Cultivation Base for Nonmetal Composites and Functional Materials, Southwest University of Science and Technology, Mianyang 621010 (China); Wang, Xin; Li, Huidong; Teng, Yuancheng [State Key Laboratory Cultivation Base for Nonmetal Composites and Functional Materials, Southwest University of Science and Technology, Mianyang 621010 (China); Peng, Long [Sichuan Province Key Laboratory of Information Materials and Devices Application, Chengdu University of Information Technology, Chengdu 610225 (China)

    2016-09-15

    The effects of sulfate content on structure and chemical durability of barium borosilicate glass-ceramics were studied. The results show that the glass-ceramics with 0–1.10 mol% SO{sub 3} possess mainly CaZrTi{sub 2}O{sub 7}-2M phase along with a small amount of CaZrTi{sub 2}O{sub 7}-3T and ZrO{sub 2} phases. The hexagonal CaZrTi{sub 2}O{sub 7}-3T crystals crystallize on the surface of glass-ceramics. For the samples with 1.24–1.55 mol% SO{sub 3}, the main crystalline phases are CaTiSiO{sub 5} and CaZrTi{sub 2}O{sub 7}-2M in the bulk, while a separate sulfate layer containing Na{sub 2}SO{sub 4} and BaSO{sub 4} is observed on the surface. X-ray fluorescence analysis indicates that about 2/3 of the SO{sub 3} originally added has been lost by volatility. The normalized mass loss (NL{sub i}) for Na, B, Ca elements remains almost unchanged (∼10{sup −2} g/m{sup 2}) after 7 days for the samples with 0–1.10 mol% SO{sub 3}. The NL{sub i} for both Na and B increases gradually after 7 days when the SO{sub 3} content is 1.24 mol%. - Highlights: • Strip-shaped CaZrTi{sub 2}O{sub 7}-2M and plate-like CaTiSiO{sub 5} crystals crystallize in the bulk. • CaZrTi{sub 2}O{sub 7}-3T crystals crystallize on the surface for samples with 0–1.10 mol% SO{sub 3}. • A separate sulfate layer crystallizes on the surface when SO{sub 3} exceeds solubility.

  6. Structure and chemical durability of barium borosilicate glass-ceramics containing zirconolite and titanite crystalline phases

    Science.gov (United States)

    Li, Huidong; Wu, Lang; Xu, Dong; Wang, Xin; Teng, Yuancheng; Li, Yuxiang

    2015-11-01

    In order to increase the solubility of actinides in the glass matrix, the effects of CaO, TiO2, and ZrSiO4 addition (abbreviated as CTZ, in the mole ratio of 2:2:1) on crystalline phases, microstructure, and chemical durability of barium borosilicate glass-ceramics were investigated. The results show that the samples possess both zirconolite-2M and titanite phase when the CTZ content is greater than or equal to 45 wt.%. For the glass-ceramics with 45 wt.% CTZ (CTZ-45), only zirconolite-2M phase is observed after annealing at 680-740 °C for 2 h. The CTZ-45 possess zirconolite-2M and titanite phases after annealing at 700 °C first, and then annealing at 900-1050 °C for 2 h. Furthermore, the zirconolite-2M and titanite grains show a strip and brick shape, respectively. The CTZ-45 annealing at 950 °C shows the lower normalized leaching rates of B, Na and Nd when compared to that of CTZ-0 and CTZ-55.

  7. Residual glass and crystalline phases in a barium disilicate glass–ceramic

    Energy Technology Data Exchange (ETDEWEB)

    Araujo, Marcel C.C. [Postgraduate Program in Materials Engineering, Federal Institute of Maranhão — IFMA, 65030-001 São Luis, MA (Brazil); Botta, Walter J. [Department of Materials Engineering, Federal University of São Carlos — UFSCar, São Carlos, SP (Brazil); Kaufmann, Michael J. [Department of Metallurgical and Materials Engineering, Colorado School of Mines, CO (United States); Angelica, Romulo S. [Geosciences Institute, Federal University of Pará— UFPA, 66075-110 Belém, PA (Brazil); Mercury, José M.R. [Postgraduate Program in Materials Engineering, Federal Institute of Maranhão — IFMA, 65030-001 São Luis, MA (Brazil); Department of Chemistry, Federal Institute of Maranhão — IFMA, 65030-001 São Luis, MA (Brazil); Cabral, Aluísio A., E-mail: aluisio_cab@yahoo.com.br [Postgraduate Program in Materials Engineering, Federal Institute of Maranhão — IFMA, 65030-001 São Luis, MA (Brazil); Department of Physics, Federal Institute of Maranhão — IFMA, 65030-001 São Luis, MA (Brazil)

    2015-12-15

    Investigations about the presence of residual glass are scarce, despite its fundamental role in the crystallization kinetics and luminescent properties of barium disilicate glass–ceramics (BaO·2SiO{sub 2}–BS{sub 2}) with a quasi-stoichiometric composition. Non-isothermal (DTA/DSC) experiments have demonstrated that BS{sub 2} presents a polymorphic transformation, where the h-BS{sub 2} (monoclinic structure) phase is completely transformed in l-BS{sub 2} (orthorhombic structure) at temperatures higher than 1020 °C (10 °C/min). In this study, BS{sub 2} monolithic samples were heat-treated at 1000 °C (BS2-10) and 1100 °C (BS2-11) in a DSC furnace at a heating rate of 10 °C/min. In addition, the crystalline and amorphous phases were characterized and quantified by Transmission Electron Microscopy (TEM) and X-ray Diffraction (XRD) experiments, respectively. Although the complete polymorphic transformation from h-BS2 to l-BS2 was achieved at 1100 °C, our results demonstrated that BS2-11 contains a minor, albeit not negligible, amount of residual glass. - Highlights: • The crystalline and amorphous phases in a barium disilicate glass were characterized and quantified by XRD and TEM. • The BS2-10 sample was constituted by two main crystalline phases, which consists of 2 polymorphic forms: h-BS2 and l-BS2. • The orthorhombic BS2 phase (l-BS2) was predominant at 1100 °C. • The complete polymorphic transformation from h-BS2 to l-BS2 was achieved at 1100 °C. • Nevertheless, our XRD and TEM results demonstrated that BS2-11 contains a minor amount of residual glass.

  8. Deposition of Crystalline Hydroxyapatite Nanoparticles on Y-TZP Ceramic: A Potential Solution to Enhance Bonding Characteristics of Y-TZP Ceramics

    Directory of Open Access Journals (Sweden)

    Abbas Azari

    2017-08-01

    Full Text Available Objectives: Many advantages have been attributed to dental zirconia ceramics in terms of mechanical and physical properties; however, the bonding ability of this material to dental structure and/or veneering ceramics has always been a matter of concern. On the other hand, hydroxyapatite (HA shows excellent biocompatibility and good bonding ability to tooth structure, with mechanically unstable and brittle characteristics, that make it clinically unacceptable for use in high stress bearing areas. The main purpose of this study was to introduce two simple yet practical methods to deposit the crystalline HA nanoparticles on zirconia ceramics. Materials and Methods: zirconia blocks were treated with HA via two different deposition methods namely thermal coating and air abrasion. Specimens were analyzed by scanning electron microscopy, energy dispersive spectroscopy (EDS and X-ray diffraction (XRD.Results: In both groups, the deposition techniques used were successfully accomplished, while the substrate showed no structural change. However, thermal coating group showed a uniform deposition of crystalline HA but in air abrasion method, there were dispersed thin islands of HA.Conclusions: Thermal coating method has the potential to significantly alter the surface characteristics of zirconia. The simple yet practical nature of the proposed method may be able to shift the bonding paradigm of dental zirconia ceramics. This latter subject needs to be addressed in future investigations.Keywords: Zirconium Oxide; Hydroxyapatites; Dental Bonding; Microscopy, Electron, Scanning; X-Ray Diffraction; Spectrometry, X-Ray Emission

  9. SHEAR BOND STRENGTHS BETWEEN CERAMIC CORES AND VENEERING CERAMICS OF DENTAL BI-LAYERED CERAMIC SYSTEMS AND THE SENSITIVITY TO THERMOCYCLING

    Directory of Open Access Journals (Sweden)

    SUN TING, BDS, DDS

    2012-09-01

    Full Text Available The purpose of this study was to investigate the bond strength between various commercial ceramic core materials and veneering ceramics of dental bi-layered ceramic combinations and the effect of thermocycling. The shear bond strength of four dental bi-layered ceramic combinations (white Cercon, yellow Cercon, white Lava, yellow Lava, IPS E.max were tested. Metal ceramic combinations were conducted as a control group. Half of each group was subjected to thermocycling. All specimens were thereafter subjected to a shear force. The initial mean shear bond strength values in MPa ± S.D were 28.02 ± 3.04 for White Cercon Base/Cercon Ceram Kiss, 27.54 ± 2.20 for Yellow Cercon Base/Cercon Ceram Kiss, 28.43 ± 2.13for White Lava Frame/Lava Ceram, 27.36 ± 2.25 for Yellow Lava Frame/Lava Ceram, 47.10 ± 3.77 for IPS E.max Press/IPS E.max Ceram and 30.11 ± 2.15 for metal ceramic control. The highest shear strength was recorded for IPS E.max Press/IPS E.max Ceram before and after thermocycling. The mean shear bond strength values of five other combinations were not significantly different (P < 0.05. Lithium-disilicate based combinations produced the highest core-veneer bonds that overwhelmed the metal ceramic combinations. Thermocycling had no effect on the core-veneer bonds. The core-veneer bonds of zirconia based combinations were not weakened by the addition of coloring pigments.

  10. Structure and chemical durability of barium borosilicate glass–ceramics containing zirconolite and titanite crystalline phases

    Energy Technology Data Exchange (ETDEWEB)

    Li, Huidong; Wu, Lang, E-mail: lang.wu@163.com; Xu, Dong; Wang, Xin; Teng, Yuancheng; Li, Yuxiang

    2015-11-15

    In order to increase the solubility of actinides in the glass matrix, the effects of CaO, TiO{sub 2}, and ZrSiO{sub 4} addition (abbreviated as CTZ, in the mole ratio of 2:2:1) on crystalline phases, microstructure, and chemical durability of barium borosilicate glass–ceramics were investigated. The results show that the samples possess both zirconolite-2M and titanite phase when the CTZ content is greater than or equal to 45 wt.%. For the glass–ceramics with 45 wt.% CTZ (CTZ-45), only zirconolite-2M phase is observed after annealing at 680–740 °C for 2 h. The CTZ-45 possess zirconolite-2M and titanite phases after annealing at 700 °C first, and then annealing at 900–1050 °C for 2 h. Furthermore, the zirconolite-2M and titanite grains show a strip and brick shape, respectively. The CTZ-45 annealing at 950 °C shows the lower normalized leaching rates of B, Na and Nd when compared to that of CTZ-0 and CTZ-55. - Highlights: • CaO, TiO{sub 2}, ZrSiO{sub 4} (CTZ) as nucleating agents were added to barium borosilicate glass. • The samples with 45–55 wt% CTZ possess CaZrTi{sub 2}O{sub 7}-2M and CaTiSiO{sub 5} crystalline phases. • CTZ-45 (45wt% CTZ) possesses only CaZrTi{sub 2}O{sub 7}-2M phase after annealing at 680–740 °C. • CTZ-45 possesses CaZrTi{sub 2}O{sub 7}-2M and CaTiSiO{sub 5} phases after annealing at 900–1050 °C. • CTZ-45 annealing at 950 °C shows the lower leaching rates of B, Na and Nd than CTZ-0 and CTZ-55.

  11. Illuminating light-dependent color shifts in core and veneer layers of dental all-ceramics

    Science.gov (United States)

    Lee, Yong-Keun; Cha, Hyun-Suk; Yu, Bin

    2014-09-01

    The color of an object is perceived differently depending on the ambient light conditions. Since dental all-ceramic restorations are fabricated by building up several layers to reproduce the tooth shade, the optical properties of each layer should be optimized for successful shade reproduction. This study aimed to determine the separate contributions of the color shifts in each of the core and veneer layers of all-ceramics by switching the illuminating lights on the color shifts of layered ceramics. Specimens of seven kinds of core ceramics and the corresponding veneer ceramics for each core were fabricated with a layered thickness of 1.5 mm. A sintering ceramic was used as a reference core material. The Commission Internationale de l'Eclairage (CIE) color coordinates of core, veneer, and layered specimens were measured with a spectroradiometer under the CIE illuminant D65 (daylight), A (incandescent lamp), and F9 (fluorescent lamp) simulating lights. Color shifts of the layered specimens were primarily determined by the CIE a* shifts (D65 to A switch) or by the CIE b* shifts (D65 to F9 switch) of the veneer layer. The color coordinates shifts in the constituent layers differentially influenced those of the layered specimens by the kind of switched lights. Therefore, the optical properties of the constituent layers of all-ceramics should be controlled to reflect these findings.

  12. Crystalline thin films: The electrochemical atomic layer deposition (ECALD) view

    CSIR Research Space (South Africa)

    Modibedi, M

    2011-09-01

    Full Text Available Electrochemical atomic layer deposition technique is selected as one of the methods to prepare thin films for various applications, including electrocatalytic materials and compound....

  13. Ceramic membranes by electrochemical vapor deposition of zirconia-yttria-terbia layers on porous substrates

    NARCIS (Netherlands)

    Brinkman, H.W.; Brinkman, Hendrik W.; Burggraaf, Anthonie; Burggraaf, Anthonie J.

    1995-01-01

    By means of electrochemical vapor deposition (EVD), it is possible to grow thin, dense layers of zirconia/yttria/terbiasolid solution (ZYT) on porous ceramic substrates. These layers can be used as ceramic membranes for oxygen separation.The kinetics of the EVD process, the morphology of the grown

  14. Shear-horizontal surface waves on piezoelectric ceramics with depolarized surface layer.

    Science.gov (United States)

    Kielczynski, P J; Pajewski, W; Szalewski, M

    1989-01-01

    Theoretical analysis and numerical results describing the propagation of SH (shear-horizontal) surface waves on piezoelectric ceramics with a depolarized surface layer are described. SH surface waves propagating in piezoelectric ceramics with a depolarized surface layer are shown to be a mixture of the Bleustein-Gulyaev surface wave, electrical potential, and the Love surface-wave mechanical displacement. Depolarization of the surface layer in piezoelectric ceramics produces strong dispersion and a multimode structure of the SH surface wave. The penetration depth of the SH surface waves propagating on an electrically free surface of a piezoelectric ceramic with a depolarized surface layer can be significantly smaller than that of the Bleustein-Gulyaev surface waves propagating on a free piezoelectric half-space. It is concluded that piezoelectric ceramics with a depolarized surface layer can be used in hybrid piezoelectric semiconductor convolvers of reduced size.

  15. Sliding Contact Fatigue Damage in Layered Ceramic Structures

    Science.gov (United States)

    Kim, Jae-Won; Kim, Joo-Hyung; Thompson, Van P.; Zhang, Yu

    2016-01-01

    Porcelain veneered restorations often chip and fracture from repeated occlusal loading, making fatigue studies relevant. Most fatigue studies are limited to uniaxial loading without sliding motion. We hypothesize that biaxial loading (contact-load-slide-liftoff, simulating a masticatory cycle) as compared to uniaxial loading accelerates the fatigue of layered ceramics. Monolithic glass plates were epoxy joined to polycarbonate substrates as a transparent model for an all-ceramic crown on dentin. Uniaxial and biaxial cyclic contact was applied through a hard sphere in water with a mouth-motion machine. The uniaxial (contact-load-hold-liftoff) and traditional R-ratio fatigue (indenter never leaves the specimen surface) produced a similar lifespan, while biaxial fatigue was more severe. The accelerated crack growth rate in biaxial fatigue is attributed to enhanced tensile stresses at the trailing edges of a moving indenter. Fracture mechanics descriptions for damage evolution in brittle materials loaded repeatedly with a sliding sphere are provided. Clinical relevance is addressed. PMID:17959894

  16. Numerical modelling of evaporation in a ceramic layer in the tape casting process

    DEFF Research Database (Denmark)

    Jabbaribehnam, Mirmasoud; Jambhekar, V. A.; Hattel, Jesper Henri

    2016-01-01

    Evaporation of water from a ceramic layer is a key phenomenon in the drying process for the manufacturing of tape cast ceramics. This process contains mass, momentum and energy exchange between the porous medium and the free-flow region. In order to analyze such interaction processes, a Represent......Evaporation of water from a ceramic layer is a key phenomenon in the drying process for the manufacturing of tape cast ceramics. This process contains mass, momentum and energy exchange between the porous medium and the free-flow region. In order to analyze such interaction processes...

  17. Modeling of water absorption induced cracks in resin-based composite supported ceramic layer structures.

    Science.gov (United States)

    Huang, Min; Thompson, V P; Rekow, E D; Soboyejo, W O

    2008-01-01

    Cracking patterns in the top ceramic layers of the modeled dental multilayers with polymer foundation are observed when they are immersed in water. This article developed a model to understand this cracking mechanism. When water diffuses into the polymer foundation of dental restorations, the foundation will expand; as a result, the stress will build up in the top ceramic layer because of the bending and stretching. A finite element model based on this mechanism is built to predict the stress build-up and the slow crack growth in the top ceramic layers during the water absorption. Our simulations show that the stress build-up by this mechanism is high enough to cause the cracking in the top ceramic layers and the cracking patterns predicted by our model are well consistent with those observed in experiments on glass/epoxy/polymer multilayers. The model is then used to discuss the life prediction of different dental ceramics.

  18. Charge transport and device physics of layered-crystalline organic semiconductors (Presentation Recording)

    Science.gov (United States)

    Hasegawa, Tatsuo

    2015-10-01

    Here we present and discuss our recent investigations into the understanding of microscopic charge transport, novel film processing technologies, and a development of layered-crystalline organic semiconductors for high performance OTFTs. We first discuss the microscopic charge transport in the OTFTs, as investigated by field-induced electron spin resonance spectroscopy. The technique can detect signals due to tiny amount of field-induced carriers, accumulated at the semiconductor-insulator interfaces. Following aspects are presented and discussed; 1) Carrier motion within the crystalline domains can be understood in terms of the trap-and-release transport, 2) charge trap states are spatially extended over several sites depending on the trap levels, and 3) the intra- and inter-domain transport can be discriminated by anisotropic electron spin resonance measurements. Next we discuss novel print production technologies for organic semiconductors showing high layered crystallinity. The concept of "printed electronics" is now regarded as a realistic paradigm to manufacture light-weight, thin, and impact-resistant electronics devices, although production of highly crystalline semiconductor films may be incompatible with conventional printing process. We here present printing techniques for manufacturing high performance OTFTs; 1) double-shot inkjet printing for small-molecule-based semiconductors, and 2) push-coating for semiconducting polymers. We demonstrate that both processes are useful to manufacture high quality semiconductor layers with the high layered crystallinity.

  19. Towards the synthesis of an experimental bioactive dental ceramic. Part I: Crystallinity characterization and bioactive behavior evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Goudouri, O.-M. [Physics Department, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece); Kontonasaki, E. [School of Dentistry, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece); Papadopoulou, L.; Kantiranis, N. [Department of Geology, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece); Lazaridis, N.K. [Chemistry Department, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece); Chrissafis, K.; Chatzistavrou, X. [Physics Department, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece); Koidis, P. [School of Dentistry, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece); Paraskevopoulos, K.M., E-mail: kpar@auth.gr [Physics Department, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece)

    2014-05-01

    An attachment between the dental ceramic and the surrounding marginal tissues in fixed prosthetic restorations could eliminate secondary carries prevalence. The development of dental ceramics with apatite forming ability could provide the biological surface required for selective spread and attachment of specific cell types able to promote tissue attachment. Dental ceramics/bioactive glass composites synthesized by the sol gel method have been previously reported to develop carbonated hydroxyapatite (HCAp) in biomimetic solutions, requiring though a high amount of bioactive glass, which resulted in the compromise of their mechanical integrity. Thus, the aim of the present work was the synthesis and characterization of an experimental sol–gel derived dental ceramic with low amount of bioactive glass and the evaluation of its in vitro bioactivity. Differential thermal and thermogravimetric analysis (TG–DTA), Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffractometry (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) were used to evaluate the crystal structure and the in vitro apatite forming ability of the synthesized material. The results of this study indicated the successful sol–gel synthesis of an experimental dental ceramic containing low amount of bioactive glass that presented similar structural and morphological characteristics with a commercial feldspathic dental ceramic, while exhibiting in vitro bioactivity. The apatite forming ability of the experimental sol–gel derived feldspathic dental ceramic may trigger the appropriate cellular mechanisms towards the establishment of attachment with the surrounding connective tissue. This attachment could provide a barrier to oral bacteria penetration, prolonging the life expectation of the restorations. - Highlights: • Synthesis of a bioactive sol–gel dental ceramic for fixed prosthetic restorations. • The sol–gel technique promoted the crystallization of

  20. Lattice-Matched Semiconductor Layers on Single Crystalline Sapphire Substrate

    Science.gov (United States)

    Choi, Sang; King, Glen; Park, Yeonjoon

    2009-01-01

    SiGe is an important semiconductor alloy for high-speed field effect transistors (FETs), high-temperature thermoelectric devices, photovoltaic solar cells, and photon detectors. The growth of SiGe layer is difficult because SiGe alloys have different lattice constants from those of the common Si wafers, which leads to a high density of defects, including dislocations, micro-twins, cracks, and delaminations. This innovation utilizes newly developed rhombohedral epitaxy of cubic semiconductors on trigonal substrates in order to solve the lattice mismatch problem of SiGe by using trigonal single crystals like sapphire (Al2O3) as substrate to give a unique growth-orientation to the SiGe layer, which is automatically controlled at the interface upon sapphire (0001). This technology is different from previous silicon on insulator (SOI) or SGOI (SiGe on insulator) technologies that use amorphous SiO2 as the growth plane. A cubic semiconductor crystal is a special case of a rhombohedron with the inter-planar angle, alpha = 90 deg. With a mathematical transformation, all rhombohedrons can be described by trigonal crystal lattice structures. Therefore, all cubic lattice constants and crystal planes (hkl) s can be transformed into those of trigonal crystal parameters. These unique alignments enable a new opportunity of perfect lattice matching conditions, which can eliminate misfit dislocations. Previously, these atomic alignments were thought to be impossible or very difficult. With the invention of a new x-ray diffraction measurement method here, growth of cubic semiconductors on trigonal crystals became possible. This epitaxy and lattice-matching condition can be applied not only to SiGe (111)/sapphire (0001) substrate relations, but also to other crystal structures and other materials, including similar crystal structures which have pointgroup rotational symmetries by 120 because the cubic (111) direction has 120 rotational symmetry. The use of slightly miscut (less than

  1. Crystalline and magnetic ordering in the monoclinic phase of the layered perovskite PAMC

    DEFF Research Database (Denmark)

    Harris, P.; Lebech, B.; Achiwa, N.

    1994-01-01

    A single-crystal elastic neutron scattering experiment between 4.2 and 115 K has been performed on the low-temperature monoclinic zeta phase of the layered perovskite bis(propylammonium) manganesetetrachloride (PAMC). The crystalline structure is commensurately modulated, with a modulation vector...

  2. Thermal resistances of crystalline and amorphous few-layer oxide thin films

    Science.gov (United States)

    Chen, Liang; Kumari, Niru; Hou, Yu

    2017-11-01

    Thermal insulation at nanoscale is of crucial importance for non-volatile memory devices such as phase change memory and memristors. We perform non-equilibrium molecular dynamics simulations to study the effects of interface materials and structures on thermal transport across the few-layer dielectric nanostructures. The thermal resistance across few-layer nanostructures and thermal boundary resistance at interfaces consisting of SiO2/HfO2, SiO2/ZrO2 or SiO2/Al2O3 are obtained for both the crystalline and amorphous structures. Based on the comparison temperature profiles and phonon density of states, we show that the thermal boundary resistances are much larger in crystalline few-layer oxides than the amorphous ones due to the mismatch of phonon density of state between distinct oxide layers. Compared with the bulk SiO2, the increase of thermal resistance across crystalline few-layer oxides results from the thermal boundary resistance while the increase of thermal resistance across amorphous few-layer oxides is attributed to the lower thermal conductivity of the amorphous thin films.

  3. Basic research in crystalline and noncrystalline ceramic systems. Annual report, August 1, 1979-October 31, 1980

    Energy Technology Data Exchange (ETDEWEB)

    Sempolinski, D. R.; Kingery, W. D.; Tuller, H. L.; Diear, J. M.; Dudney, N. J.; Coble, R. L.; French, R.; Cheng, K. W.; Giraldez, E.; Henriksen, A. F.; Kijima, K.; Gattuso, T. R.; Dolhert, L.; Gambino, J.; Yager, T. A.; Chiang, Y. M.; Tajima, Y.; Dynys, J. M.; Cannon, Jr., R. M.; Kuo-Wen, Tsui; Hong, W.; Handwerker, C. A.; Schneibel, J. H.; Zelinski, B.

    1980-01-01

    The Basic Research Programs in Ceramics supports a significant fraction of the research effort and graduate student training in ceramics at M.I.T. The importance of basic research programs in ceramics processing and properties is becoming widely recognized as the critical role of improved ceramic materials for energy systems is acknowledged. The needs identified in the 1977 series of workshops on DOE programs in energy-related materials research and by the ongoing efforts of the DOE Council on Materials Science are being translated into the basic and applied research necessary to fulfill the established objectives in the effort to solve the nation's energy problems. Present indications are that ceramics in numerous applications will be critical in meeting national energy requirements.

  4. Preparation of electron buffer layer with crystalline ZnO nanoparticles in inverted organic photovoltaic cells

    Science.gov (United States)

    Lee, Donghwan; Kang, Taeho; Choi, Yoon-Young; Oh, Seong-Geun

    2017-06-01

    Zinc oxide (ZnO) nanoparticles synthesized through sol-gel method were used to fabricate the electron buffer layer in inverted organic photovoltaic cells (OPVs) after thermal treatment. To investigate the effect of thermal treatment on the formation of crystalline ZnO nanoparticles, the amorphous ZnO nanoparticles were treated via hydrothermal method. The crystalline phase of ZnO with well-ordered structure could be obtained when the amorphous phase of ZnO was processed under hydrothermal treatment at 170 °C. The crystalline structure of ZnO thin film in inverted organic solar cell could be obtained under relatively low annealing temperature by using thermally treated ZnO nanoparticles. The OPVs fabricated by using crystalline ZnO nanoparticles for electron buffer layer exhibited higher efficiency than the conventional ZnO nanoparticles. The best power conversion efficiency (PCE) was achieved for 7.16% through the ZnO film using the crystalline ZnO nanoparticles. The proposed method to prepared ZnO nanoparticles (NPs) could effectively reduce energy consumption during the fabrication of OPVs, which would greatly contribute to advantages such as lower manufacturing costs, higher productivity and application on flexible substrates.

  5. Modeling and Simulation of Ballistic Penetration of Ceramic-Polymer-Metal Layered Systems

    Science.gov (United States)

    2016-01-01

    and penetration by tungsten alloy rods into composite targets consisting of layers of aluminum nitride ceramic tile(s), polymer laminae, and aluminum ...representation of such interfaces may be overly compliant. The present results emphasize the importance of proper resolution of geometry and constitutive...ballistic impact and penetration by tungsten alloy rods into composite targets consisting of layers of aluminum nitride ceramic tile(s), polymer laminae

  6. Graphene Quantum Dot Layers with Energy-Down-Shift Effect on Crystalline-Silicon Solar Cells.

    Science.gov (United States)

    Lee, Kyung D; Park, Myung J; Kim, Do-Yeon; Kim, Soo M; Kang, Byungjun; Kim, Seongtak; Kim, Hyunho; Lee, Hae-Seok; Kang, Yoonmook; Yoon, Sam S; Hong, Byung H; Kim, Donghwan

    2015-09-02

    Graphene quantum dot (GQD) layers were deposited as an energy-down-shift layer on crystalline-silicon solar cell surfaces by kinetic spraying of GQD suspensions. A supersonic air jet was used to accelerate the GQDs onto the surfaces. Here, we report the coating results on a silicon substrate and the GQDs' application as an energy-down-shift layer in crystalline-silicon solar cells, which enhanced the power conversion efficiency (PCE). GQD layers deposited at nozzle scan speeds of 40, 30, 20, and 10 mm/s were evaluated after they were used to fabricate crystalline-silicon solar cells; the results indicate that GQDs play an important role in increasing the optical absorptivity of the cells. The short-circuit current density was enhanced by about 2.94% (0.9 mA/cm(2)) at 30 mm/s. Compared to a reference device without a GQD energy-down-shift layer, the PCE of p-type silicon solar cells was improved by 2.7% (0.4 percentage points).

  7. Evaluation of Fracture Toughness of Tantalum Carbide Ceramic Layer: A Vickers Indentation Method

    Science.gov (United States)

    Song, Ke; Xu, Yunhua; Zhao, Nana; Zhong, Lisheng; Shang, Zhao; Shen, Liuliu; Wang, Juan

    2016-07-01

    A tantalum carbide (TaC) ceramic layer was produced on gray cast iron matrix by in situ technique comprising a casting process and a subsequent heat treatment at 1135 °C for 45 min. Indentation fracture toughness in TaC ceramic layer was determined by the Vickers indentation test for various loads. A Niihara approach was chosen to assess the fracture toughness of TaC ceramic layer under condition of the Palmqvist mode in the experiment. The results reveal that K IC evaluation of TaC ceramic layer by the Vickers indentation method strongly depends on the selection of crack system and K IC equations. The critical indentation load for Vickers crack initiation in TaC ceramic layer lies between 1 and 2 N and the cracks show typical intergranular fracture characteristics. Indentation fracture toughness calculated by the indentation method is independent of the indentation load on the specimen. The fracture toughness of TaC ceramic layer is 6.63 ± 0.34 MPa m1/2, and the toughening mechanism is mainly crack deflection.

  8. Studies of void growth in a thin ductile layer between ceramics

    DEFF Research Database (Denmark)

    Tvergaard, Viggo

    1997-01-01

    The growth of voids in a thin ductile layer between ceramics is analysed numerically, using an axisymmetric cell model to represent an array of uniformly distributed spherical voids at the central plane of the layer. The purpose is to determine the full traction-separation law relevant to crack...... growth by a ductile mechanism along the thin layer. Plastic flow in the layer is highly constrained by the ceramics, so that a high. level of triaxial tension develops, leading in some cases to cavitation instabilities. The computations are continued to a state near the occurrence of void coalescence....

  9. Crystallinity of inorganic films grown by atomic layer deposition: Overview and general trends

    Science.gov (United States)

    Miikkulainen, Ville; Leskelä, Markku; Ritala, Mikko; Puurunen, Riikka L.

    2013-01-01

    Atomic layer deposition (ALD) is gaining attention as a thin film deposition method, uniquely suitable for depositing uniform and conformal films on complex three-dimensional topographies. The deposition of a film of a given material by ALD relies on the successive, separated, and self-terminating gas-solid reactions of typically two gaseous reactants. Hundreds of ALD chemistries have been found for depositing a variety of materials during the past decades, mostly for inorganic materials but lately also for organic and inorganic-organic hybrid compounds. One factor that often dictates the properties of ALD films in actual applications is the crystallinity of the grown film: Is the material amorphous or, if it is crystalline, which phase(s) is (are) present. In this thematic review, we first describe the basics of ALD, summarize the two-reactant ALD processes to grow inorganic materials developed to-date, updating the information of an earlier review on ALD [R. L. Puurunen, J. Appl. Phys. 97, 121301 (2005)], and give an overview of the status of processing ternary compounds by ALD. We then proceed to analyze the published experimental data for information on the crystallinity and phase of inorganic materials deposited by ALD from different reactants at different temperatures. The data are collected for films in their as-deposited state and tabulated for easy reference. Case studies are presented to illustrate the effect of different process parameters on crystallinity for representative materials: aluminium oxide, zirconium oxide, zinc oxide, titanium nitride, zinc zulfide, and ruthenium. Finally, we discuss the general trends in the development of film crystallinity as function of ALD process parameters. The authors hope that this review will help newcomers to ALD to familiarize themselves with the complex world of crystalline ALD films and, at the same time, serve for the expert as a handbook-type reference source on ALD processes and film crystallinity.

  10. Prediction of crack propagation in layered ceramics with strong interfaces

    Czech Academy of Sciences Publication Activity Database

    Náhlík, Luboš; Šestáková, L.; Hutař, Pavel; Bermejo, R.

    2010-01-01

    Roč. 77, č. 11 (2010), s. 2192-2199 ISSN 0013-7944 R&D Projects: GA AV ČR(CZ) KJB200410803; GA ČR GA101/09/1821 Institutional research plan: CEZ:AV0Z20410507 Keywords : Ceramic laminate * Crack propagation direction * Residual stress * Flaw tolerant ceramics * Optimal design Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 1.571, year: 2010

  11. Modelling of a thin soft layer on a self-lubricating ceramic composite

    NARCIS (Netherlands)

    Valefi, Mahdiar; de Rooij, Matthias B.; Mokhtari, Milad; Schipper, Dirk J.

    2013-01-01

    Friction and wear of a self-lubricating ceramic composite under unlubricated sliding contact conditions is dependent on the formation and regeneration of a thin soft surface layer. Experimental observations have shown that a thin soft layer (third body) may be formed depending on the tribological

  12. Cracks in nano-ceramic thin layers produced by laser treatments

    NARCIS (Netherlands)

    De Hosson, JTM; Teeuw, DHJ; Beltz, GE; Selinger, RLB; Kim, KS; Marder, MP

    1999-01-01

    Sol-gel derived thin nano-ceramic layers of TiO2 and Al2O3 are studied using scanning electron microscopy to reveal the microstructure and morphologies of the layers. The low-voltage scanning electron microscope with a field emission gun is equipped with an especially designed lens, where the

  13. Surface Recombination of Crystalline Silicon Substrates Passivated by Atomic-Layer-Deposited AlOx

    Science.gov (United States)

    Arafune, Koji; Miki, Shohei; Matsutani, Ryosuke; Hamano, Junpei; Yoshida, Haruhiko; Tachibana, Tomihisa; Lee, Hyun Ju; Ogura, Atsuhi; Ohshita, Yoshio; Satoh, Shin-ichi

    2012-04-01

    AlOx films as passivation layers for p-type crystalline silicon were prepared by atomic layer deposition with ozone as an oxidant, and the effects of the AlOx film thickness and deposition temperature on the maximum recombination velocity (Smax) were evaluated. Smax is improved by increasing the layer thickness but saturates at a layer thickness of about 30 nm. In the case of samples deposited at room temperature, Smax is improved fivefold when the thickness is increased from 20 to 33 nm. Smax also improved as the deposition temperature was increased to 300 °C then deteriorated when it was further increased to 350 °C. After postdeposition annealing, we obtained an Smax of 8.5 cm/s.

  14. Synthesis of steel slag ceramics: chemical composition and crystalline phases of raw materials

    Science.gov (United States)

    Zhao, Li-hua; Wei, Wei; Bai, Hao; Zhang, Xu; Cang, Da-qiang

    2015-03-01

    Two types of porcelain tiles with steel slag as the main raw material (steel slag ceramics) were synthesized based on the CaO-Al2O3-SiO2 and CaO-MgO-SiO2 systems, and their bending strengths up to 53.47 MPa and 99.84 MPa, respectively, were obtained. The presence of anorthite, α-quartz, magnetite, and pyroxene crystals (augite and diopside) in the steel slag ceramics were very different from the composition of traditional ceramics. X-ray diffraction (XRD) and electron probe X-ray microanalysis (EPMA) results illustrated that the addition of steel slag reduced the temperature of extensive liquid generation and further decreased the firing temperature. The considerable contents of glass-modifying oxide liquids with rather low viscosities at high temperature in the steel slag ceramic adobes promoted element diffusion and crystallization. The results of this study demonstrated a new approach for extensive and effective recycling of steel slag.

  15. Fabrication of ceramic layer-by-layer infrared wavelength photonic band gap crystals

    Science.gov (United States)

    Kang, Henry Hao-Chuan

    Photonic band gap (PBG) crystals, also known as photonic crystals, are periodic dielectric structures which form a photonic band gap that prohibit the propagation of electromagnetic (EM) waves of certain frequencies at any incident angles. Photonic crystals have several potential applications including zero-threshold semiconductor lasers, the inhibiting spontaneous emission, dielectric mirrors, and wavelength filters. If defect states are introduced in the crystals, light can be guided from one location to another or even a sharp bending of light in submicron scale can be achieved. This generates the potential for optical waveguide and optical circuits, which will contribute to the improvement in the fiber-optic communications and the development of high-speed computers. The goal of this dissertation research is to explore techniques for fabricating 3D ceramic layer-by-layer (LBL) photonic crystals operating in the infrared frequency range, and to characterize the infilling materials properties that affect the fabrication process as well as the structural and optical properties of the crystals. While various approaches have been reported in literature for the fabrication of LBL structure, the uniqueness of this work ties with its cost-efficiency and relatively short process span. Besides, very few works have been reported on fabricating ceramic LBL crystals at mid-IR frequency range so far. The fabrication techniques reported here are mainly based on the concepts of microtransfer molding with the use of polydimethyl siloxane (PDMS) as molds/stamps. The infilling materials studied include titanium alkoxide precursors and aqueous suspensions of nanosize titania particles (slurries). Various infilling materials were synthesized to determine viscosities, effects on drying and firing shrinkages, effects on film surface roughness, and their moldability. Crystallization and phase transformation of the materials were also monitored using DTA, TGA and XRD. Mutilayer crystal

  16. Effect of different aging methods on the mechanical behavior of multi-layered ceramic structures.

    Science.gov (United States)

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

    2016-12-01

    To evaluate the effect of two aging methods (mechanical cycling and autoclave) on the mechanical behavior of veneer and framework ceramic specimens with different configurations (monolithic, two and three-layers). Three ceramics used as framework for fixed dental prostheses (YZ-Vita In-Ceram YZ; IZ-Vita In-Ceram Zirconia; AL-Vita In-Ceram AL) and two veneering porcelains (VM7 and VM9) were studied. Bar-shaped specimens were produced in three different designs: monolithic, two layers (porcelain-framework) and three layers (porcelain-framework-porcelain). Specimens were tested for three-point flexural strength at 1MPa/s in 37°C artificial saliva. Three different experimental conditions were evaluated (n=10): control; mechanical cycling (2Hz, 37°C artificial saliva); and autoclave aging (134°C, 2 bars, 5h). Bi-layered specimens were tested in both conditions: with porcelain or framework ceramic under tension. Fracture surfaces were analyzed using stereomicroscope and scanning electron microscopy. Results were statistically analyzed using Kruskal-Wallis and Student-Newman-Keuls tests. Only for AL group, mechanical cycling and autoclave aging significantly decreased the flexural strength values in comparison to the control (paging methods evaluated also had no effect on strength (p≥0.05). Total and partial failure modes were identified. Mechanical cycling and autoclave aging protocols had no effect on the flexural strength values and failure behavior of YZ and IZ ceramic structures. Yet, AL monolithic structures showed a significant decrease in flexural strength with any of the aging methods. Copyright © 2016. Published by Elsevier Ltd.

  17. Flexural strength of a layered zirconia and porcelain dental all-ceramic system.

    Science.gov (United States)

    White, S N; Miklus, V G; McLaren, E A; Lang, L A; Caputo, A A

    2005-08-01

    New processing techniques have facilitated the use of zirconia core materials in all-ceramic dental prostheses. Zirconia has many potential advantages compared to existing core materials; however, its performance when layered with porcelain has not been evaluated. This study investigated the strength of a wide variety of layered zirconia and porcelain beams to determine whether the inclusion of zirconia cores results in improved strength. Eight types of layered or simple zirconia and porcelain beams (n = 10), approximately fixed partial denture-size, were made of a tetragonal polycrystalline zirconium dioxide partially stabilized with yttria core (Lava System Frame) and a feldspathic dental porcelain (Lava Ceram veneer ceramic). Elastic moduli of the materials were measured using an acoustic method. Maximum force and modulus of rupture were determined using 3-point flexural testing and a universal testing machine. Descriptive statistical methods were used. Beams with porcelain tensile surfaces recorded mean tensile strengths or moduli of rupture from 77 to 85 MPa, whereas beams with zirconia tensile surfaces recorded moduli of rupture almost an order of magnitude higher, 636 to 786 MPa. The elastic moduli of the porcelain and zirconia materials were 71 and 224 GPa, respectively. Crack propagation following initial tensile cracking often involved the porcelain-zirconia interface, as well as bulk porcelain and zirconia. The layered zirconia-porcelain system tested recorded substantially higher moduli of rupture than have been previously reported for other layered all-ceramic systems.

  18. Study of stacked-emitter layer for high efficiency amorphous/crystalline silicon heterojunction solar cells

    Science.gov (United States)

    Lee, Youngseok; Kim, Heewon; Iftiquar, S. M.; Kim, Sunbo; Kim, Sangho; Ahn, Shihyun; Lee, Youn-Jung; Dao, Vinh Ai; Yi, Junsin

    2014-12-01

    A modified emitter, of stacked two layer structure, was investigated for high-efficiency amorphous/crystalline silicon heterojunction (HJ) solar cells. Surface area of the cells was 181.5 cm2. The emitter was designed to achieve a high open circuit voltage (Voc) and fill factor (FF). When doping of the emitter layer was increased, it was observed that the silicon dihydride related structural defects within the films increased, and the Voc of the HJ cell decreased. On the other hand, while the doping concentration of the emitter was reduced the FF of the cell reduced. Therefore, a combination of a high conductivity and low defects of a single emitter layer appears difficult to obtain, yet becomes necessary to improve the cell performance. So, we investigated a stacked-emitter with low-doped/high-doped double layer structure. A low-doped emitter with reduced defect density was deposited over the intrinsic hydrogenated amorphous silicon passivation layer, while the high-doped emitter with high conductivity was deposited over the low-doped emitter. The effects of doping and defect density of the emitter, on the device performance, were elucidated by using computer simulation and an optimized device structure was formulated. The simulation was performed with the help of Automat for the Simulation of Heterostructures simulation software. Finally, based on the simulation results, amorphous/crystalline heterojunction silicon solar cells were optimized by reducing density of defect states in the stacked-emitter structure and we obtained 725 mV, 77.41%, and 19.0% as the open-circuit voltage, fill factor, and photo-voltaic conversion efficiency of the device, respectively.

  19. Monodisperse gold nanoparticles formed on bacterial crystalline surface layers (S-layers) by electroless deposition

    Energy Technology Data Exchange (ETDEWEB)

    Dieluweit, S. [Center for Nanobiotechnology, University of Natural Resources and Applied Life Sciences (BOKU), Gregor Mendel-Strasse 33, A-1180 Vienna (Austria); Pum, D. [Center for Nanobiotechnology, University of Natural Resources and Applied Life Sciences (BOKU), Gregor Mendel-Strasse 33, A-1180 Vienna (Austria); Sleytr, U.B. [Center for Nanobiotechnology, University of Natural Resources and Applied Life Sciences (BOKU), Gregor Mendel-Strasse 33, A-1180 Vienna (Austria); Kautek, W. [Department for Physical Chemistry, University of Vienna, Waehringer Strasse 42, A-1090 Vienna (Austria)]. E-mail: wolfgang.kautek@univie.ac.at

    2005-12-15

    The fabrication of patterned arrays of nanoparticles whose electronic, optical and magnetic properties will find technological applications, such as ultra-high-density memories, is currently one of the most important objectives of inorganic material research. In this study, the in situ electroless nucleation of ordered two-dimensional arrays of gold nanoparticles (5 nm in size) by using bacterial S-layers as molecular templates and their characterization by small spot X-ray photoelectron emission spectroscopy (XPS) is presented. This yielded the elemental composition of the nanoclusters, which consisted of almost entirely elemental gold, and possible side reactions on the cluster and protein surface. The preferential deposition of the gold nanoparticles on the S-layer suggests that topography and functional groups are important for superlattice formation.

  20. The influence of superficial properties of ceramic-metal layers on acoustic emission

    Directory of Open Access Journals (Sweden)

    В.П. Бабак

    2005-03-01

    Full Text Available  The influence of idle time on operational properties of friction pairs with ceramic-metal superficial layers is investigated in this article. The application of AE information for the control and diagnostics of complex tribotechnical systems directly during their operation is offered.

  1. A mechanical model for surface layer formation on self-lubricating ceramic composites

    NARCIS (Netherlands)

    Song, Jiupeng; Valefi, Mahdiar; de Rooij, Matthias B.; Schipper, Dirk J.

    2010-01-01

    To predict the thickness of a self-lubricating layer on the contact surface of ceramic composite material containing a soft phase during dry sliding test, a mechanical model was built to calculate the material transfer of the soft second phase in the composite to the surface. The tribological test,

  2. Electrical and structural properties of nano-crystalline silicon intrinsic layers for nano-crystalline silicon solar cells prepared by very high frequency plasma chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, P.; Zhu, F. [Department of Metallurgical and Materials Engineering, Colorado School of Mines, Colorado 80401 (United States); Madan, A. [Department of Metallurgical and Materials Engineering, Colorado School of Mines, Colorado 80401 (United States); MVSystems Inc, Golden Colorado 80401 (United States)

    2008-07-15

    Thin silicon intrinsic layers were deposited in the amorphous to nano-crystalline transition regime to investigate their structural and optoelectrical properties using the very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD) technique. Optical emission spectroscopy (OES) was primarily used to monitor the plasma properties during the deposition. The ratio H{alpha}/Si{sup *}, estimated from OES spectra, is closely related to the microstructure of the films. With the increasing plasma power from 10 to 50 W, the ratio H{alpha}/Si{sup *} increases leading to nano-crystalline films. The ratio H{alpha}/Si{sup *} decreases with the increase of process gas pressure at constant power of 15 and 30 W. The films were nano-crystalline at low pressure and became amorphous at high pressure. (author)

  3. Selective deposition contact patterning using atomic layer deposition for the fabrication of crystalline silicon solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Young Joon [Graduate School of Energy Science and Technology, Chungnam National University, Yuseong-gu, Daejeon 305-764 (Korea, Republic of); Shin, Woong-Chul [NCD Co. Ltd., Yuseong-gu, Daejeon 305-509 (Korea, Republic of); Chang, Hyo Sik, E-mail: hschang@cnu.ac.kr [Graduate School of Energy Science and Technology, Chungnam National University, Yuseong-gu, Daejeon 305-764 (Korea, Republic of)

    2014-10-01

    Selective deposition contact (SDC) patterning was applied to fabricate the rear side passivation of crystalline silicon (Si) solar cells. By this method, using screen printing for contact patterning and atomic layer deposition for the passivation of Si solar cells with Al{sub 2}O{sub 3}, we produced local contacts without photolithography or any laser-based processes. Passivated emitter and rear-contact solar cells passivated with ozone-based Al{sub 2}O{sub 3} showed, for the SDC process, an up-to-0.7% absolute conversion-efficiency improvement. The results of this experiment indicate that the proposed method is feasible for conversion-efficiency improvement of industrial crystalline Si solar cells. - Highlights: • We propose a local contact formation process. • Local contact forms a screen print and an atomic layer deposited-Al{sub 2}O{sub 3} film. • Ozone-based Al{sub 2}O{sub 3} thin film was selectively deposited onto patterned silicon. • Selective deposition contact patterning method can increase cell-efficiency by 0.7%.

  4. Crystalline Bacterial Surface Layer (S-Layer) Opens Golden Opportunities for Nanobiotechnology in Textiles.

    Science.gov (United States)

    Asadi, Narges; Chand, Nima; Rassa, Mehdi

    2015-12-01

    This study focuses on the successful recrystallization of bacterial S-layer arrays of the Lactobacillus acidophilus ATCC 4356 at textile surfaces to create a novel method and material. Optimum bacterial growth was obtained at approximately 45 °C, pH 5.0, and 14 h pi. The cells were resuspended in guanidine hydrochloride and the 43 kDa S-protein was dialyzed and purified. The optimum reassembly on the polypropylene fabric surface in terms of scanning electron microscopy (SEM), reflectance, and uniformity (spectrophotometry) was obtained at 30 °C, pH 5.0 for 30 minutes in the presence of 2 gr/l (liquor ratio; 1:40) of the S-protein. Overall, our data showed that the functional aspects and specialty applications of the fabric would be very attractive for the textile and related sciences, and result in advanced technical textiles.

  5. Gettering impurities from crystalline silicon by aluminum diffusion using a porous silicon layer

    Energy Technology Data Exchange (ETDEWEB)

    Khedher, N.; Hajji, M.; Bessais, B.; Ezzaouia, H.; Bennaceur, R. [Laboratoire des Applications Solaires, Institut National de Recherche Scientifique et Technique, BP. 95, Hammam Lif (Tunisia); Selmi, A. [Laboratoire de Physique des Semi-conducteurs, Faculte des Sciences de Monastir, 5000 Monastir (Tunisia)

    2005-06-01

    In this paper, we report a study on the possibility of gettering transition metal impurities from solar grade crystalline silicon (Si). Porous silicon layers were formed by the stain-etching method on both sides of the Si wafer. Aluminum diffusion was done throughout the PS layer in an infrared furnace under a (N{sub 2}/O{sub 2}) controlled atmosphere. This enables to getter eventual metal impurities towards the PS layer. The gettering effect was evaluated by measuring the majority carrier density and mobility and the minority carrier diffusion length (L{sub d}) of the Si substrate. For this purpose, Wander Pauw and Hall Effect measurements together with the Light Beam Induced Current (LBIC) technique were used. We noticed that the best gettering corresponds to a heat treatment at 850 C for 30 min; in that case an evident decrease of the majority carrier density and an enhancement of the mobility were observed. After gettering, we found an apparent improvement of the minority carrier diffusion length. These results give evidence of the effectiveness of external gettering treatments by combining (Al-PS) layer for an efficient gettering effect in solar grade monocrystalline Si. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  6. Light trapping of crystalline Si solar cells by use of nanocrystalline Si layer plus pyramidal texture

    Energy Technology Data Exchange (ETDEWEB)

    Imamura, Kentaro; Nonaka, Takaaki; Onitsuka, Yuya; Irishika, Daichi; Kobayashi, Hikaru, E-mail: h.kobayashi@sanken.osaka-u.ac.jp

    2017-02-15

    Highlights: • Ultralow reflectivity Si wafers with light trapping effect can be obtained by forming a nanocrystalline Si layer on pyramidal textured Si surfaces. • Surface passivation using phosphosilicate glass improved minority carrier lifetime of the nanocrystalline Si layer/Si structure. • A high photocurrent density of 40.1 mA/cm{sup 2}, and a high conversion efficiency of 18.5% were achieved. - Abstract: The surface structure chemical transfer (SSCT) method has been applied to fabrication of single crystalline Si solar cells with 170 μm thickness. The SSCT method, which simply involves immersion of Si wafers in H{sub 2}O{sub 2} plus HF solutions and contact of Pt catalyst with Si taking only ∼30 s for 6 in. wafers, can decrease the reflectivity to less than 3% by the formation of a nanocrystalline Si layer. However, the reflectivity of the nanocrystalline Si layer/flat Si surface/rear Ag electrode structure in the wavelength region longer than 1000 nm is high because of insufficient absorption of incident light. The reflectivity in the long wavelength region is greatly decreased by the formation of the nanocrystalline Si layer on pyramidal textured Si surfaces due to an increase in the optical path length. Deposition of phosphosilicate glass (PSG) on the nanocrystalline Si layer for formation of pn-junction does not change the ultralow reflectivity because the surface region of the nanocrystalline Si layer possesses a refractive index of 1.4 which is nearly the same as that of PSG of 1.4–1.5. The PSG layer is found to passivate the nanocrystalline Si layer, which is evident from an increase in the minority carrier lifetime from 12 to 44 μs. Hydrogen treatment at 450 °C further increases the minority carrier lifetime approximately to a doubled value. The solar cells with the layer/pyramidal Si substrate/boron-diffused back surface field/Ag rear electrode> structure show a high conversion efficiency of 18

  7. Crystalline structure and squeeze-out dissipation of liquid solvation layers observed by small-amplitude dynamic AFM

    Science.gov (United States)

    Hofbauer, W.; Ho, R. J.; Hairulnizam, R.; Gosvami, N. N.; O'Shea, S. J.

    2009-10-01

    Using frequency-modulation atomic force microscopy (FM-AFM) at sub-nanometer vibration amplitudes, we find in the system n -dodecanol/graphite that solvation layers may extend for several nanometers into the bulk liquid. These layers maintain crystalline order which can be imaged using FM-AFM. The energy dissipation of the vibrating tip can peak sharply upon penetration of molecular layers. The tip shape appears critical for this effect.

  8. Low-Temperature Crystalline Titanium Dioxide by Atomic Layer Deposition for Dye-Sensitized Solar Cells

    KAUST Repository

    Chandiran, Aravind Kumar

    2013-04-24

    Low-temperature processing of dye-sensitized solar cells (DSCs) is crucial to enable commercialization with low-cost, plastic substrates. Prior studies have focused on mechanical compression of premade particles on plastic or glass substrates; however, this did not yield sufficient interconnections for good carrier transport. Furthermore, such compression can lead to more heterogeneous porosity. To circumvent these problems, we have developed a low-temperature processing route for photoanodes where crystalline TiO2 is deposited onto well-defined, mesoporous templates. The TiO2 is grown by atomic layer deposition (ALD), and the crystalline films are achieved at a growth temperature of 200 C. The ALD TiO2 thickness was systematically studied in terms of charge transport and performance to lead to optimized photovoltaic performance. We found that a 15 nm TiO2 overlayer on an 8 μm thick SiO2 film leads to a high power conversion efficiency of 7.1% with the state-of-the-art zinc porphyrin sensitizer and cobalt bipyridine redox mediator. © 2013 American Chemical Society.

  9. Controlling the Spatial Organization of Liquid Crystalline Nanoparticles by Composition of the Organic Grafting Layer.

    Science.gov (United States)

    Wójcik, Michał M; Olesińska, Magdalena; Sawczyk, Michał; Mieczkowski, Józef; Górecka, Ewa

    2015-07-06

    Understanding how the spatial ordering of liquid crystalline nanoparticles can be controlled by different factors is of great importance in the further development of their photonic applications. In this paper, we report a new key parameter to control the mesogenic behavior of gold nanoparticles modified by rodlike thiols. An efficient method to control the spatial arrangement of hybrid nanoparticles in a condensed state is developed by changing the composition of the mesogenic grafting layer on the surface of the nanoparticles. The composition can be tuned by different conditions of the ligand exchange reaction. The thermal and optical behavior of the mesogenic and promesogenic ligands were investigated by using differential scanning calorimetry (DSC) and hot-stage polarized optical microscopy. The chemical structure of the synthesized hybrid nanoparticles was characterized by (1) H NMR spectroscopy, thermogravimetric analysis (TGA), XPS, and elemental analysis, whereas the superstructures were examined by small-angle X-ray diffraction (SAXSRD) analysis. Structural studies showed that the organic sublayer made of mesogenic ligands is denser with an increasing the average ligand number, thereby separating the nanoparticles in the liquid crystalline phases, which changes the parameters of these phases. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Immunochemical detection of prion protein on dipsticks prepared with crystalline bacterial cell-surface layers.

    Science.gov (United States)

    Völkel, Dirk; Zimmermann, Klaus; Breitwieser, Andreas; Pable, Sabrina; Glatzel, Markus; Scheiflinger, Friedrich; Schwarz, Hans P; Sara, Margit; Sleytr, Uwe B; Dorner, Friedrich

    2003-12-01

    Transmissible spongiform encephalopathy (TSE) represents a spectrum of diseases affecting humans and animals. A definitive diagnosis of TSEs is only possible by postmortem identification of pathologic prion protein in brain tissue that has been treated with protease. The pathologic protein is detected by Western blot analysis or ELISA methods. The bovine spongiform encephalopathy crisis and occurrence of a new variant of CJD has increased demand for rapid and simple assays. A dipstick assay has been developed for prion diagnosis based on a sandwich ELISA specific for prion protein, and crystalline bacterial cell-surface layers (S-layers) were used as an immobilization matrix. The usefulness of the dipstick assay was evaluated by determining the detection limit, comparison with other methods, and analysis of CJD samples. The sensitivity of the prion dipsticks was similar to that published for time-resolved fluorescence ELISA methods. After protease treatment, pathologic prion protein could be detected specifically. The dipstick assay is a sensitive and specific test useful for the detection of prion protein. The simplicity of the S-layer dipstick lends itself to a variety of potential applications including field diagnostics.

  11. Evaluation of shear bond strength between zirconia core and ceramic veneers fabricated by pressing and layering techniques: In vitro study.

    Science.gov (United States)

    Subash, M; Vijitha, D; Deb, Saikat; Satish, A; Mahendirakumar, N

    2015-08-01

    Although ceramic veneered on to zirconia core have been in use for quite some time, information regarding the comparative evaluation of the Shear bond strength of Pressable & Layered ceramic veneered on to zirconia core is limited. To evaluate the shear bond strength of zirconia core and ceramic veneer fabricated by two different techniques, Layering (Noritake CZR) and Pressing (Noritake, CZR Press). 20 samples of zirconia blocks were fabricated and the samples were divided into group A & B. Group A - Ceramic Veneered over zirconia core by pressing using Noritake CZR Press. Group B - Ceramic Veneered over zirconia core by layering using Noritake CZR. The veneered specimens were mounted on to the center of a PVC tube using self-cure acrylic resin leaving 3 mm of the veneered surface exposed as cantilever. Using a Universal testing machine the blocks were loaded up to failure. The results were tabulated by using independent samples t-test. The mean shear bond strength for Pressed specimens was 12.458 ± 1.63(S.D) MPa and for layered specimens was 8.458 ± 0.845(S.D) MPa. Pressed specimens performed significantly better than the layered specimen with a P value 0.001. Clinicians and dental laboratory technicians should consider the use of pressed ceramics as an alternative to traditional layering procedures to reduce the chances of chipping or de-lamination of ceramics.

  12. Strength and thickness of the layer of materials used for ceramic veneers bonding.

    Science.gov (United States)

    Mazurek, Karolina; Mierzwińska-Nastalska, Elżbieta; Molak, Rafał; Kożuchowski, Mariusz; Pakieła, Zbigniew

    2012-01-01

    The use of adhesive bonding systems and composites in prosthetic dentistry brought improved and more aesthetic prosthetic restorations. The adhesive bonding of porcelain veneers is based on the micromechanical and chemical bond between tooth surface, cement layer and ceramic material. The aim of the study was to measure the thickness of the material layer formed during cementing of a ceramic restoration, and - in the second part of the study - to test tension of these cements. The materials investigated comprised dual-curing materials: Variolink II, KoNroot Cem, KoNroot Cem Viscous and Panavia F 2.0, as well as a light-curing composite: Variolink Veneer. The thickness was measured with the use of ZIP Lite 250 optical gauging apparatus. SEM microscope - Hitachi Tabletop Microscope TM-100 - was used to analyse the characteristics of an adhesive bond and filler particle size of particular materials. Tension tests of the cements under study were carried out on the MTS Q Test 10 static electrodynamic apparatus. The tests showed that KoNroot Cem exhibited the best mechanical properties of bonding to enamel and dentin among the materials tested. Variolink II base light-curing cement formed the thinnest layer. All the materials tested formed the layer not exceeding 1/3 of ceramic restoration thickness.

  13. Barium hydroxide hole blocking layer for front- and back-organic/crystalline Si heterojunction solar cells

    Science.gov (United States)

    Hossain, Jaker; Kasahara, Koji; Harada, Daisuke; Saiful Islam, A. T. M.; Ishikawa, Ryo; Ueno, Keiji; Hanajiri, Tatsuro; Nakajima, Yoshikata; Fujii, Yasuhiko; Tokuda, Masahide; Shirai, Hajime

    2017-08-01

    We demonstrate the potential of barium hydroxide, Ba(OH)2, as a hole blocking layer on the photovoltaic performance of front- and back-organic/n-type crystalline silicon (n-Si) heterojunction solar cells with poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)(PEDOT:PSS). The power conversion efficiency (PCE) of the front-PEDOT:PSS/n-Si heterojunction solar cell was increased from 12.8% for pristine to 13.6% with a 2-nm-thick Ba(OH)2 interlayer at the rear n-Si and aluminum (Al) cathode interface due to the enhanced hole blocking as well as electron injection capability to the Al cathode in the infrared region. PCE was further increased to 14.3% with a short-circuit density JSC of 30.27 mA/cm2, an open-circuit voltage VOC of 0.632 V, and a fill factor FF of 0.75 using a 20-nm-thick 4,4'-Cyclohexylidenebis[N,N-bis(4-methylphenyl)benzenamine] as an antireflection layer. PCE of the back-PEDOT:PSS/n-Si heterojunction solar cells was also increased from 4.4% for pristine to 8.1% with a JSC of 33.40 mA/cm2, a VOC of 0.573 V, and an FF of 0.423 by inserting a 2-nm-thick Ba(OH)2 layer at the front-Al and isotropically textured n-Si interface. These findings imply that Ba(OH)2 has great potential as an efficient hole-blocking layer for both front- and back-PEDOT:PSS/n-Si heterojunction solar cells.

  14. Structural phase analysis of a sol-gel nano-crystalline lithium-mica glass-ceramic through different compositions

    Energy Technology Data Exchange (ETDEWEB)

    Tohidifar, M.R., E-mail: tohidifar@znu.ac.ir [Faculty of Engineering, University of Zanjan, P.O. Box 45371-38791, Zanjan (Iran, Islamic Republic of); Alizadeh, P. [Department of Materials Science and Engineering, Tarbiat Modares University, P.O. Box 14115-143, Tehran (Iran, Islamic Republic of)

    2016-08-15

    The current paper attempts to study the influence of chemical composition on the phase development of nano-crystalline lithium-mica glass-ceramic. For this purpose, aqueous sol-gel technique was employed to prepare the glass-ceramics. The synthesis process was accomplished using two chemical compositions of Li{sub (1+x)}Mg{sub 3}AlSi{sub 3(1+x)}O{sub 10+6.5x}F{sub 2} and LiMg{sub 3}AlSi{sub 3(1+x)}O{sub 10+6x}F{sub 2} at different x values along with various mass% of MgF{sub 2} inclusion. It was found that considering an optimized amount of MgF{sub 2}, the specimens synthesized through a new formulation of LiMg{sub 3}AlSi{sub 3(1+x)}O{sub 10+6x}F{sub 2} composition are more appropriate for the sol-gel synthesis method, especially because of intensifying the lithium-mica precipitation and also omission of the secondary phase (i.e. lithium aluminum silicate). The results also indicated that any deviation from the optimized amount of MgF{sub 2} (8%) would cause degradation in the intensity of the precipitated lithium-mica, following the nucleation treatment. - Highlights: • Higher intensity of mica phase obtains through LiMg{sub 3}AlSi{sub 3(1+x)}O{sub 10+6x}F{sub 2} composition. • LiMg{sub 3}AlSi{sub 3(1+x)}O{sub 10+6x}F{sub 2} composition offers mica phase without applying excess MgF{sub 2}. • Applying LiMg{sub 3}AlSi{sub 3(1+x)}O{sub 10+6x}F{sub 2} composition leads to omission of minor phases. • Li{sub (1+x)}Mg{sub 3}AlSi{sub 3(1+x)}O{sub 10+6.5x}F{sub 2} formula cannot be useful in mica nucleation process. • Optimum amount of MgF{sub 2} was obtained as 8% following the nucleation process.

  15. A gel-ceramic multi-layer electrolyte for long-life lithium sulfur batteries.

    Science.gov (United States)

    Wang, Qingsong; Wen, Zhaoyin; Jin, Jun; Guo, Jing; Huang, Xiao; Yang, Jianhua; Chen, Chunhua

    2016-01-28

    A newly designed gel-ceramic multi-layer electrolyte has been used as the separator and electrolyte for lithium sulfur (Li-S) batteries. The Li-S cells, free of the shuttle effect, exhibit superior electrochemical performance. With almost no self-discharge, the cell demonstrates an initial discharge specific capacity of up to 725 mA h g(-1) and remains at 700 mA h g(-1) after 300 cycles at the C/2 rate.

  16. Improving impact resistance of ceramic materials by energy absorbing surface layers

    Science.gov (United States)

    Kirchner, H. P.; Seretsky, J.

    1974-01-01

    Energy absorbing surface layers were used to improve the impact resistance of silicon nitride and silicon carbide ceramics. Low elastic modulus materials were used. In some cases, the low elastic modulus was achieved using materials that form localized microcracks as a result of thermal expansion anisotropy, thermal expansion differences between phases, or phase transformations. In other cases, semi-vitreous or vitreous materials were used. Substantial improvements in impact resistance were observed at room and elevated temperatures.

  17. High Gain and High Directive of Antenna Arrays Utilizing Dielectric Layer on Bismuth Titanate Ceramics

    Directory of Open Access Journals (Sweden)

    F. H. Wee

    2012-01-01

    Full Text Available A high gain and high directive microstrip patch array antenna formed from dielectric layer stacked on bismuth titanate (BiT ceramics have been investigated, fabricated, and measured. The antennas are designed and constructed with a combination of two-, four-, and six-BiT elements in an array form application on microwave substrate. For gain and directivity enhancement, a layer of dielectric was stacked on the BiT antenna array. We measured the gain and directivity of BiT array antennas with and without the dielectric layer and found that the gain of BiT array antenna with the dielectric layer was enhanced by about 1.4 dBi of directivity and 1.3 dB of gain over the one without the dielectric layer at 2.3 GHz. The impedance bandwidth of the BiT array antenna both with and without the dielectric layer is about 500 MHz and 350 MHz, respectively, which is suitable for the application of the WiMAX 2.3 GHz system. The utilization of BiT ceramics that covers about 90% of antenna led to high radiation efficiency, and small-size antennas were produced. In order to validate the proposed design, theoretical and measured results are provided and discussed.

  18. A combined SEM, CV and EIS study of multi-layered porous ceramic reactors for flue gas purification

    DEFF Research Database (Denmark)

    He, Zeming; Andersen, Kjeld Bøhm; Nygaard, Frederik Berg

    2013-01-01

    The effect of sintering temperature of 12-layered porous ceramic reactors (comprising 5 cells) was studied using scanning electron microscopy (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The difference in microstructures of the reactors was evaluated by SEM...

  19. An Investigation on a Crystalline-Silicon Solar Cell with Black Silicon Layer at the Rear.

    Science.gov (United States)

    Zhou, Zhi-Quan; Hu, Fei; Zhou, Wen-Jie; Chen, Hong-Yan; Ma, Lei; Zhang, Chi; Lu, Ming

    2017-12-15

    Crystalline-Si (c-Si) solar cell with black Si (b-Si) layer at the rear was studied in order to develop c-Si solar cell with sub-band gap photovoltaic response. The b-Si was made by chemical etching. The c-Si solar cell with b-Si at the rear was found to perform far better than that of similar structure but with no b-Si at the rear, with the efficiency being increased relatively by 27.7%. This finding was interesting as b-Si had a large specific surface area, which could cause high surface recombination and degradation of solar cell performance. A graded band gap was found to form at the rear of the c-Si solar cell with b-Si layer at the rear. This graded band gap tended to expel free electrons away from the rear, thus reducing the probability of electron-hole recombination at b-Si and improving the performance of c-Si solar cell.

  20. Room-temperature vacancy migration in crystalline Si from an ion-implanted surface layer

    DEFF Research Database (Denmark)

    Larsen, Arne Nylandsted; Christensen, Carsten; Petersen, Jon Wulff

    1999-01-01

    Migration of vacancies in crystalline, n-type silicon at room temperature from Ge+-implanted (150 keV, 5×109–1×1011 cm–2) surface layers was studied by tracing the presence of P–V pairs (E centers) in the underlying layer using deep level transient spectroscopy (DLTS). Under the conditions we have...... examined, the vacancies migrate to a maximum depth of about 1 µm and at least one vacancy per implanted Ge ion migrates into the silicon crystal. The annealing of the E centers is accompanied, in an almost one-to-one fashion, by the appearance of a new DLTS line corresponding to a level at EC......–Et[approximate]0.15 eV that has donor character. It is argued that the center associated with this line is most probably the P2–V complex; it anneals at about 550 K. A lower limit of the RT-diffusion coefficient of the doubly charged, negative vacancy is estimated to be 4×10–11 cm2/s. ©1999 American Institute...

  1. Plastic damage induced fracture behaviors of dental ceramic layer structures subjected to monotonic load.

    Science.gov (United States)

    Wang, Raorao; Lu, Chenglin; Arola, Dwayne; Zhang, Dongsheng

    2013-08-01

    The aim of this study was to compare failure modes and fracture strength of ceramic structures using a combination of experimental and numerical methods. Twelve specimens with flat layer structures were fabricated from two types of ceramic systems (IPS e.max ceram/e.max press-CP and Vita VM9/Lava zirconia-VZ) and subjected to monotonic load to fracture with a tungsten carbide sphere. Digital image correlation (DIC) and fractography technology were used to analyze fracture behaviors of specimens. Numerical simulation was also applied to analyze the stress distribution in these two types of dental ceramics. Quasi-plastic damage occurred beneath the indenter in porcelain in all cases. In general, the fracture strength of VZ specimens was greater than that of CP specimens. The crack initiation loads of VZ and CP were determined as 958 ± 50 N and 724 ± 36 N, respectively. Cracks were induced by plastic damage and were subsequently driven by tensile stress at the elastic/plastic boundary and extended downward toward to the veneer/core interface from the observation of DIC at the specimen surface. Cracks penetrated into e.max press core, which led to a serious bulk fracture in CP crowns, while in VZ specimens, cracks were deflected and extended along the porcelain/zirconia core interface without penetration into the zirconia core. The rupture loads for VZ and CP ceramics were determined as 1150 ± 170 N and 857 ± 66 N, respectively. Quasi-plastic deformation (damage) is responsible for crack initiation within porcelain in both types of crowns. Due to the intrinsic mechanical properties, the fracture behaviors of these two types of ceramics are different. The zirconia core with high strength and high elastic modulus has better resistance to fracture than the e.max core. © 2013 by the American College of Prosthodontists.

  2. A randomized controlled clinical trial of 3-unit posterior zirconia-ceramic fixed dental prostheses (FDP) with layered or pressed veneering ceramics: 3-year results.

    Science.gov (United States)

    Naenni, Nadja; Bindl, Andreas; Sax, Caroline; Hämmerle, Christoph; Sailer, Irena

    2015-11-01

    The aim of the present pilot study was to test whether or not posterior zirconia-ceramic fixed dental prostheses (FDPs) with pressed veneering ceramic exhibit less chipping than FDPs with layered veneering ceramics. Forty patients (13 female, 27 male; mean age 54 years (range 26.1-80.7 years) in need of one maxillary or mandibular three-unit FDP in the second premolar or molar region were recruited and treated at two separate centers at the University of Zurich according to the same study protocol. The frameworks were made out of zirconia using a CAD/CAM system (Cerec Sirona, Bensheim, Germany). The patients were randomly assigned to either the test group (zirconia frameworks veneered with pressed ceramic; IPS e.max ZirPress, Ivoclar Vivadent AG, Schaan, Liechtenstein; n=20) or the control group (layered veneering ceramic; IPS e.max Ceram, Ivoclar Vivadent AG, Schaan, Liechtenstein; n=20). All FDPs were adhesively cemented and evaluated at baseline (i.e., cementation), at 6 months and at 1 and 3 years of clinical service. The survival of the reconstruction was recorded. The technical outcome was assessed using modified United States Public Health Services (USPHS) criteria. The biologic parameters analyzed at abutment teeth and analogous non-restored teeth included probing pocket depth (PPD), plaque control record (PCR), bleeding on probing (BOP), and tooth vitality (CO2). Data was descriptively analyzed and survival was calculated using Kaplan-Meier statistics. 36 patients (25 female, 11 male; mean age 52.3 years) with 18 test and 18 control FDPs were examined after a mean follow-up of 36 months (95% CI: 32.6-39.1 months). Comparison of groups was done by Crosstabulation showing even distribution of the respective restored teeth amidst the groups. Survival rate was 100% for both test and control FDPs. Chipping of the veneering ceramic tended to occur more frequently in test (n=8; 40%) than in control (n=4; 20%) FDPs, albeit not significantly (p=0.3). No further

  3. Transparent layered YAG ceramics with structured Yb doping produced via tape casting

    Science.gov (United States)

    Hostaša, Jan; Piancastelli, Andreana; Toci, Guido; Vannini, Matteo; Biasini, Valentina

    2017-03-01

    The flexibility of the ceramic production process, in particular in terms of shaping and spatial control of distribution of active ions, is one of the strong points in favor of transparent ceramics. In high power lasers in particular, where thermal management is a critical issue, the finely controlled design of spatial distribution of the doping ions within the laser gain media can reduce undesired thermally induced effects and large temperature gradients, and thus enhance the efficiency and laser beam quality especially under increased thermal load. In the present work transparent structured YAG ceramics with Yb doping were produced by tape casting followed by thermal compression of assembled tapes and sintered under high vacuum. The thermal compression of variously doped tape cast layers is a very promising method because it allows a high precision and good control over dopant distribution in the sintered material. After sintering, the distribution of Yb across the layers was characterized by SEM-EDX and the thickness of Yb diffusion zones between the layers with different Yb content was measured. Optical homogeneity was assessed by means of optical transmittance mapping of the samples and by 2D scanning of laser output. The effect of structured dopant distribution on laser performance was measured in quasi-CW and CW regime with different duty factors. Slope efficiency values higher than 50% were measured both in quasi-CW and in CW lasing conditions. The results are in good agreement with previously calculated predictions, confirming the beneficial effect of structured doping on laser performances and enlightening the impact of the residual scattering losses. Compared to other processing methods, such as the pressing of granulated powders, tape casting followed by thermal compression leads to straight and narrow interfaces between layers with different composition and allows to build structures composed of extremely thin layers with defined dopant content.

  4. The influence of porcelain layer thickness on the final shade of ceramic restorations.

    Science.gov (United States)

    Dozić, Alma; Kleverlaan, Cornelis Johannes; Meegdes, Marcel; van der Zel, Jef; Feilzer, Albert Joseph

    2003-12-01

    Ceramic restorations should be made of porcelain layers of different opacity, shade, and thickness in order to provide a natural appearance. By means of CAD/CAM layering technology such as CICERO, it is feasible to produce all-ceramic crowns with porcelain layers of predetermined thickness. However, it is not yet known whether changes in thickness of these porcelain layers within the clinically available space can perceivably influence the overall shade of the restoration. The purpose of this study was to determine, quantitatively, the effect of different thickness ratios of opaque porcelain (OP) and translucent porcelain (TP) layers on the overall shade of all-ceramic specimens. The CIELAB values of 5 assembled specimens, each consisting of 2 or 3 discs (CORE 0.70 mm/OP--0, 0.25, 0.50, 0.75, or 1.00 mm/TP 1.00, 0.75, 0.50, 0.25, or 0 mm) were determined with a spectrophotometer for the Vita shades A1, A2, and A3. Distilled water was used to attain optical contact between the layers. Black or white backgrounds were used to assess the influence of the background on the final shade. Color differences (DeltaE) between layered specimens were determined. Correlation between the thickness ratio and the L*, a*, and b* values was calculated by 2-tailed Spearman correlation analysis. The results indicated that small changes in OP/TP thickness ratio can perceivably influence the final shade of the layered specimens (DeltaE>1). Redness a* and yellowness b* increased with the thickness of OP for all shades. Redness a* (P<.01 for all shades) correlated more strongly with thickness than yellowness b* (P<.01 for A1 and A3; P<.05 for A2). The lightness (L*) was shade dependent. The correlation (r) between OP/TP thickness and L* was 0.975 (P<.01) for shade A1, 0.700 (not statistically significant) for shade A2, and 0.900 (P<.05) for shade A3. Small changes in thickness and shade of opaque and translucent porcelain layers can influence the final shade of the layered porcelain

  5. Three-unit posterior zirconia-ceramic fixed dental prostheses (FDPs) veneered with layered and milled (CAD-on) veneering ceramics: 1-year follow-up of a randomized controlled clinical trial

    OpenAIRE

    Grohmann, Philipp; Bindl, Andreas; Hämmerle, Christoph; Mehl, Albert; Sailer, Irena

    2015-01-01

    The aim of this multicenter randomized controlled clinical trial was to test posterior zirconia-ceramic fixed dental prostheses (FDPs) veneered with a computer-aided design/computer- assisted manufacture (CAD/CAM) lithium disilicate veneering ceramic (CAD-on) and manually layered zirconia veneering ceramic with respect to survival of the FDPs, and technical and biologic outcomes.

  6. A particle swarm-based algorithm for optimization of multi-layered and graded dental ceramics.

    Science.gov (United States)

    Askari, Ehsan; Flores, Paulo; Silva, Filipe

    2017-10-04

    The thermal residual stresses (TRSs) generated owing to the cooling down from the processing temperature in layered ceramic systems can lead to crack formation as well as influence the bending stress distribution and the strength of the structure. The purpose of this study is to minimize the thermal residual and bending stresses in dental ceramics to enhance their strength as well as to prevent the structure failure. Analytical parametric models are developed to evaluate thermal residual stresses in zirconia-porcelain multi-layered and graded discs and to simulate the piston-on-ring test. To identify optimal designs of zirconia-based dental restorations, a particle swarm optimizer is also developed. The thickness of each interlayer and compositional distribution are referred to as design variables. The effect of layers number constituting the interlayer between two based materials on the performance of graded prosthetic systems is also investigated. The developed methodology is validated against results available in literature and a finite element model constructed in the present study. Three different cases are considered to determine the optimal design of graded prosthesis based on minimizing (a) TRSs; (b) bending stresses; and (c) both TRS and bending stresses. It is demonstrated that each layer thickness and composition profile have important contributions into the resulting stress field and magnitude. Copyright © 2017 Elsevier Ltd. All rights reserved.

  7. High-peak power, passively Q-switched, composite, all-poly-crystalline ceramics Nd:YAG/Cr4+:YAG laser and generation of 532-nm green light

    Science.gov (United States)

    Salamu, G.; Ionescu, A.; Brandus, C. A.; Sandu, O.; Pavel, N.; Dascalu, T.

    2011-10-01

    Output performances of passively Q-switched, composite Nd:YAG/Cr4+:YAG lasers that consisted of bonded, all-poly-crystalline ceramics Nd:YAG and Cr4+:YAG are reported. Laser pulses at 1.06 μm with 2.5-mJ energy and 1.9-MW peak power are obtained from a 1.1-at % Nd:YAG/Cr4+:YAG ceramics that was quasi-continuous-wave (quasi-CW) pumped with a diode laser. Single-pass frequency doubling with LiB3O5 (LBO) nonlinear crystal at room temperature yielded green laser pulses at 532 nm of 0.36-mJ energy and 0.3-MW peak power, with a conversion efficiency of 0.27.

  8. Sacrificial Paste for Fabrication of Ceramic Materials by Layer-By-Layer Method

    Directory of Open Access Journals (Sweden)

    Falkowski P.

    2016-09-01

    Full Text Available The aim of the work was to develop a sacrificial paste suitable for securing channels during shaping of ceramic materials with internal structures via combination of tape casting and soft lithography. Poly(ethylene glycol methyl ether and polyethylene glycols with different molecular weight were selected as a main components of a sacrificial paste due to their compatibility to UV curable dispersion. The research shows that sacrificial paste should be characterized by proper melting point. This goal was achieved by using a composition of PEG600 with 15wt.%PEG20000 and 10wt.% carbon. The invented sacrificial paste solidify beyond 27°C (melting point. After heating up to 80°C the viscosity of paste is low enough and easily fills the channels with diameter of 150-300μm. What is more, the operational time during free cooling from 80°C to solidification is around 8 minutes what gives enough time for application. Carbon was added as a modifier of rheological properties and as a black dye that helps in visual evaluation of a degree of filling channel. The first test proved that proposed method of preparation of ceramic samples with application of invented sacrificial paste is reliable and can be practically applied.

  9. Effects of Contact Damage and Residual Stress in Dental Layered Ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Chung, J.W.; Choi, S.C. [Hanyang University, Seoul (Korea)

    2000-03-01

    Effects of contact damage and residual stress for two kinds of dental restorative layered ceramics, porcelain/alumina and porcelain/zirconia bilayers, were observed with Hertzian and Vickers indentation methods. Indentation stress-strain behavior of each material, strength degradation of the coating material, and crack propagation behavior in the coating layer after Vickers indentation were examined by and optical microscope. As a result, porcelain as coating materials showed the classical brittleness. It was inferred that damage and strength in two bilayer systems were dependent on thermal expansion mismatch between the coating material and the substrate, which affected the strength degradation. Residual stress resulting from thermal expansion mismatch was formed in the coating layer, and specially in the case of porcelain/zirconia, residual stress was eliminated as coating thickness decreased. (author). 17 refs., 6 figs.

  10. Direct bioactive ceramics coating via reactive Growing Integration Layer method on α-Ti-alloy.

    Science.gov (United States)

    Huang, Chi-Huang; Chen, Rong-Sheng; Yoshimura, Masahiro

    2017-07-01

    This paper demonstrates Ca-P-rich bio-ceramic and hydroxyapatite (HA) coatings formed directly from the solution of calcium acetate (CA) and sodium dihydrogen phosphate (SDP) on α-Ti-alloy substrates by Growing Integration Layer (GIL) technology under DC power supply. The composition of the α-Ti-alloy was Ti7Cu5Sn. The GIL coated films formed in 30min time with different voltages applied had porous and rough ceramic surfaces. They consisted mostly of various oxides like rutile, anatase, and calcium phosphates (including hydroxyapatite) that reduce corrosion rate and increase biocompatibility. An important feature was the reduction of Cu at the surfaces of the alloys. Furthermore, along with the applied voltage, the content of HA, the size of micro-pores, and hardness all increased, while the number of micro-pores in the ceramic membrane got reduced. The potential, current and resistance of corrosion were identified by potentiodynamic (PD) polarization and electrochemical impedance spectroscopy (EIS). The higher applied voltage improved the surface quality, HA formation rate, and the anti-corrosion behavior. Consequently, the samples - prepared at 350V and surface current density of 3A/cm(2) - possessed the most compact HA films, and also had the best corrosion resistance - in 0.9wt% NaCl solution at 37±1°C. Copyright © 2017. Published by Elsevier B.V.

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

    Science.gov (United States)

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

    2014-01-01

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

  12. Modeling and Simulation of Ballistic Penetration of Ceramic-Polymer-Metal Layered Systems

    Directory of Open Access Journals (Sweden)

    J. D. Clayton

    2015-01-01

    Full Text Available Numerical simulations and analysis of ballistic impact and penetration by tungsten alloy rods into composite targets consisting of layers of aluminum nitride ceramic tile(s, polymer laminae, and aluminum backing are conducted over a range of impact velocities on the order of 1.0 to 1.2 km/s. Computational results for ballistic efficiency are compared with experimental data from the literature. Simulations and experiments both demonstrate a trend of decreasing ballistic efficiency with increasing impact velocity. Predicted absolute residual penetration depths often exceed corresponding experimental values. The closest agreement between model and experiment is obtained when polymer interfaces are not explicitly represented in the numerical calculations, suggesting that the current model representation of such interfaces may be overly compliant. The present results emphasize the importance of proper resolution of geometry and constitutive properties of thin layers and interfaces between structural constituents for accurate numerical evaluation of performance of modern composite protection systems.

  13. Computer-aided study of key factors determining high mechanical properties of nanostructured surface layers in metal-ceramic composites

    Science.gov (United States)

    Konovalenko, Igor S.; Shilko, Evgeny V.; Ovcharenko, Vladimir E.; Psakhie, Sergey G.

    2017-12-01

    The paper presents the movable cellular automaton method. It is based on numerical models of surface layers of the metal-ceramic composite NiCr-TiC modified under electron beam irradiation in inert gas plasmas. The models take into account different geometric, concentration and mechanical parameters of ceramic and metallic components. The authors study the contributions of key structural factors in mechanical properties of surface layers and determine the ranges of their variations by providing the optimum balance of strength, strain hardening and fracture toughness.

  14. Preparation and Characterization of Microfiltration Ceramic Membranes Based on Natural Quartz Sand

    Directory of Open Access Journals (Sweden)

    Andrei Ivanets

    2017-06-01

    Full Text Available The effect of phase and chemical composition of natural quartz sand, binder and burnable additives was studied. The conditions of application of the membrane and biocide layers on the formation of porous ceramic and microfiltration membranes were investigated. It is shown that a crystalline oxide of Si(IV is determinant for obtaining the ceramic materials. The presence of carbonates (calcite, dolomite, aragonite, etc. and crystalline aluminosilicates (microcline, albite, phlogopit, etc. leads to a decrease in mechanical strength of ceramics. The biocide coating designed to protect the ceramic membrane surfaces from biofouling was applied and its anti-bacterial activity was shown.

  15. Design maps for failure of all-ceramic layer structures in concentrated cyclic loading

    Science.gov (United States)

    Bhowmick, Sanjit; Meléndez-Martínez, Juan José; Zhang, Yu; Lawn, Brian R.

    2009-01-01

    A study is made of the competition between failure modes in ceramic-based bilayer structures joined to polymer-based substrates, in simulation of dental crown-like structures with a functional but weak “veneer” layer bonded onto a strong “core” layer. Cyclic contact fatigue tests are conducted in water on model flat systems consisting of glass plates joined to glass, sapphire, alumina or zirconia support layers glued onto polycarbonate bases. Critical numbers of cycles to take each crack mode to failure are plotted as a function of peak contact load on failure maps showing regions in which each fracture mode dominates. In low-cycle conditions, radial and outer cone cracks are competitive in specimens with alumina cores, and outer cone cracks prevail in specimens with zirconia cores; in high-cycle conditions, inner cone cracks prevail in all cases. The roles of other factors, e.g. substrate modulus, layer thickness, indenter radius and residual stresses from specimen preparation, are briefly considered. PMID:19562095

  16. Comparison of alternative adhesive cementation concepts for zirconia ceramic: glaze layer vs zirconia primer.

    Science.gov (United States)

    Cura, Cenk; Özcan, Mutlu; Isik, Gül; Saracoglu, Ahmet

    2012-02-01

    Zirconia-based ceramics offer strong restorations in dentistry, but the adhesive bond strength of resin cements to such ceramics is not optimal. This study evaluated the bond strength of silane/adhesive/resin cement and zirconia primer/resin cement combinations on non-glazed and glazed zirconia surfaces before and after aging. Disk-shaped zirconia ceramic specimens (diameter: 8 mm; thickness: 2 mm) (N = 80, n = 10 per group) were randomly divided into 2 groups. While half of the specimens received one coat of glaze and were later finished by grinding, the other half was only ground using 1200-grit silicone carbide abrasives under water. The glazed specimens were then conditioned with 9.5% HF acid gel for 60 s, rinsed with water for 90 s, and neutralized. The glazed and non-glazed specimens were further divided into two groups. Two resin cements, namely, Variolink II and Multilink Automix were adhered onto the zirconia surfaces with their corresponding adhesive systems. In the Variolink II group, zirconia surfaces were silanized (Monobond-S), and adhesive resin (Heliobond) was applied and photopolymerized. In the Multilink Automix group, one coat of Metal/Zirconia Primer was applied with a microbrush, left to react for 180 s, and dried using oil-free air. Half of the specimens in each cement group were subjected to 5000 thermocycles (5°C to 55°C) and the other half was kept in the dark for 24 h at 37°C prior to testing. Specimens were mounted in the jig of the universal testing machine, and force was applied to the ceramic/cement interface until failure occurred (1 mm/min). After evaluating all debonded specimens under SEM, the failure types were defined as either "adhesive" with no cement left on the zirconia (score 0) or "mixed" with less than half of the cement left on the surface with no cohesive failure of the substrate (score 1). Data were analyzed using three-way ANOVA and Dunnett-T3 post-hoc tests. Application of a glaze layer significantly improved the

  17. Layer morphology and Al implant profiles after annealing of supersaturated, single-crystalline, amorphous, and nanocrystalline SiC

    Science.gov (United States)

    Heera, V.; Mücklich, A.; Dubois, C.; Voelskow, M.; Skorupa, W.

    2004-09-01

    Al supersaturated SiC layers (5×1020Alcm-3) were produced by multienergy, high-dose ion implantation into 6H- and 4H-SiC. Several implantation schemes with varying implantation sequence and temperature were investigated. In dependence on the implantation conditions damaged single-crystalline, amorphous, or nanocrystalline layers were formed. The layer morphology and Al distribution in the as-implanted state as well as structural changes and related Al redistribution after high-temperature annealing (1500-1700°C) were characterized by cross-sectional transmission electron microscopy, Rutherford backscattering spectrometry in combination with ion channeling, atomic force microscopy, and secondary-ion mass spectrometry. Remarkable Al redistribution effects have been found after annealing of Al supersaturated SiC. During high-temperature annealing Al atoms in excess to the solid solubility (2×1020Alcm-3) tend to precipitate in single-crystalline SiC whereas they diffuse out in amorphous or nanocrystalline SiC. Redistribution of Al with concentration below the solid solubility is governed by transient enhanced diffusion which can be controlled by the annealing scheme. Amorphization of SiC is advantageous in the case of Al doping to levels higher than the solid solubility because it prevents Al precipitation during annealing and helps to form boxlike Al profiles with smooth plateau and abrupt edge.

  18. Selective recovery of catalyst layer from supporting matrix of ceramic-honeycomb-type automobile catalyst.

    Science.gov (United States)

    Kim, Wantae; Kim, Boungyoung; Choi, Doyoung; Oki, Tatsuya; Kim, Sangbae

    2010-11-15

    Natural resources of platinum group metals (PGMs) are limited and their demand is increasing because of their extensive uses in industrial applications. The low rate of production of PGMs due to low concentration in the related natural ores and high cost of production have made the recovery of PGMs from previously discarded catalytic converters a viable proposition. The ceramic-honeycomb-type automobile catalytic converter contains appreciable amount of PGMs. These valuable substances, which are embedded in the catalyst layer and covered on the surface of the supporting matrix, were selectively recovered by attrition scrubbing. The attrition scrubbing was effective for the selective recovery of catalyst layer. The process was convinced as the comminution and separation process by physical impact and shearing action between particles in the scrubbing vessel. The catalyst layer was dislodged from the surface of the supporting matrix into fine particles by attrition scrubbing. The recovery of Al(2)O(3) and total PGMs in the fraction less than 300 μm increased with the residence time whereas their contents in the recovered materials slightly decreased. The interparticle scrubbing became favorable when the initial input size increased. However, the solid/liquid ratio in the mixing vessel was slightly affected by the low density of converter particles. Copyright © 2010 Elsevier B.V. All rights reserved.

  19. ZnS top layer for enhancement of the crystallinity of CZTS absorber during the annealing

    DEFF Research Database (Denmark)

    Cazzaniga, Andrea Carlo; Crovetto, Andrea; Ettlinger, Rebecca Bolt

    2015-01-01

    Pulsed Laser Deposition (PLD) of thin films of Cu2ZnSnS4 (CZTS) has not yet led to solar cells with high efficiency. The reason for the relative low efficiency is discussed and a way to overcome this issue is presented. The present thin film absorbers of CZTS suffer from loss of volatile Zn durin...... crystalline quality of CZTS after the annealing, as demonstrated by X-ray diffraction and Raman spectroscopy....

  20. Analyses of layer-thickness effects in bilayered dental ceramics subjected to thermal stresses and ring-on-ring tests

    Energy Technology Data Exchange (ETDEWEB)

    Hsueh, Chun-Hway [ORNL; Thompson, G. A. [U.S. Army Dental and Trauma Research Detachment, Greak Lakes; Jadaan, Osama M. [University of Wisconsin, Platteville; Wereszczak, Andrew A [ORNL; Becher, Paul F [ORNL

    2008-01-01

    Objectives. The purpose of this study was to analyze the stress distribution through the thickness of bilayered dental ceramics subjected to both thermal stresses and ring-on-ring tests and to systematically examine how the individual layer thickness influences this stress distribution and the failure origin. Methods. Ring-on-ring tests were performed on In-Ceram Alumina/Vitadur Alpha porcelain bilayered disks with porcelain in the tensile side, and In-Ceram Alumina to porcelain layer thickness ratios of 1:2, 1:1, and 2:1 were used to characterize the failure origins as either surface or interface. Based on the thermomechanical properties and thickness of each layer, the cooling temperature from glass transition temperature, and the ring-on-ring loading configuration, the stress distribution through the thickness of the bilayer was calculated using closed-form solutions. Finite element analyses were also performed to verify the analytical results. Results. The calculated stress distributions showed that the location of maximum tension during testing shifted from the porcelain surface to the In-Ceram Alumina/porcelain interface when the relative layer thickness ratio changed from 1:2 to 1:1 and to 2:1. This trend is in agreement with the experimental observations of the failure origins. Significance. For bilayered dental ceramics subjected to ring-on-ring tests, the location of maximum tension can shift from the surface to the interface depending upon the layer thickness ratio. The closed-form solutions for bilayers subjected to both thermal stresses and ring-on-ring tests are explicitly formulated which allow the biaxial strength of the bilayer to be evaluated.

  1. 2D crystalline protein layers as immobilization matrices for the development of DNA microarrays.

    Science.gov (United States)

    Scheicher, Sylvia R; Kainz, Birgit; Köstler, Stefan; Reitinger, Norbert; Steiner, Nicole; Ditlbacher, Harald; Leitner, Alfred; Pum, Dietmar; Sleytr, Uwe B; Ribitsch, Volker

    2013-02-15

    There is a growing demand for functional layers for the immobilization of (bio)molecules on different kinds of substrates in the field of biosensors, microarrays, and lab-on-a-chip development. These functional coatings should have the ability to specifically bind (bio)molecules with a high binding efficiency, while showing low unspecific binding during the following assay. In this paper we present rSbpA surface layer proteins (S-layer proteins) as a versatile immobilization layer for the development of DNA microarrays. S-layer proteins show the ability to reassemble into two-dimensional arrays on solid surfaces and their functional groups, such as carboxylic groups, are repeated with the periodicity of the lattice, allowing for immobilization of other (bio)molecules. Different fluorescently labeled amino functionalized DNA oligomers were covalently linked to the S-layer matrices to allow the characterization of DNA binding on S-layers. Hybridization and dissociation of DNA-oligomers were studied on S-layer coated slides, revealing low levels of unspecific adsorption of DNA on S-layer based immobilization matrices. In the following the principle was transferred to a DNA microarray design showing successful spotting and hybridization on whole microarray slides. Besides common laser scanning for fluorescence detection, S-layer based microarrays were evaluated with a compact, low cost platform for direct fluorescence imaging based on surface plasmon enhanced fluorescence excitation. It could be shown that S-layer protein layers are promising as immobilization matrices for the development of biosensors and microarrays. Copyright © 2012 Elsevier B.V. All rights reserved.

  2. Liquid-crystalline state of the wall-adjacent layers of some polar liquids

    National Research Council Canada - National Science Library

    Derjaguin, B.V; Popovskij, Yu.M; Altoiz, B.A

    1992-01-01

    ... of some polar liquids, of interfaces separating boundary layers with modified properties from the bulk liquid phase (1). The existence of such an interface was established, for example, in work (2) when studying the local values of viscosity in the wall-adjacent layers of sebacine-amyl ester. Figure 1 represents the dependence calculated according to data (2)...

  3. A facile method to enhance the uniformity and adhesion properties of water-based ceramic coating layers on hydrophobic polyethylene separators

    Science.gov (United States)

    Lee, Hoogil; Jeon, Hyunkyu; Gong, Seokhyeon; Ryou, Myung-Hyun; Lee, Yong Min

    2018-01-01

    To enhance the uniformity and adhesion properties of water-based ceramic coating layers on hydrophobic polyethylene (PE) separators, their surfaces were treated with thin and hydrophilic polydopamine layers. As a result, an aqueous ceramic coating slurry consisting of Al2O3 particles, carboxyl methyl cellulose (CMC) binders, and water solvent was easily spread on the separator surface, and a uniform ceramic layer was formed after solvent drying. Moreover, the ceramic coating layer showed greatly improved adhesion properties to the PE separator surface. Whereas the adhesion strength within the bulk coating layer (Fmid) ranged from 43 to 86 N m-1 depending on the binder content of 1.5-3.0 wt%, the adhesion strength at the interface between the ceramic coating layer and PE separator (Fsepa-Al2O3) was 245-360 N m-1, a value equivalent to an increase of four or five times. Furthermore, an additional ceramic coating layer of approximately 7 μm did not degrade the ionic conductivity and electrochemical properties of the bare PE separators. Thus, all the LiMn2O4/graphite cells with ceramic-coated separators delivered an improved cycle life and rate capability compared with those of the control cells with bare PE separators.

  4. Crystallinity Improvement of ZnO Thin Film on Different Buffer Layers Grown by MBE

    Directory of Open Access Journals (Sweden)

    Shao-Ying Ting

    2012-01-01

    Full Text Available The material and optical properties of ZnO thin film samples grown on different buffer layers on sapphire substrates through a two-step temperature variation growth by molecular beam epitaxy were investigated. The thin buffer layer between the ZnO layer and the sapphire substrate decreased the lattice mismatch to achieve higher quality ZnO thin film growth. A GaN buffer layer slightly increased the quality of the ZnO thin film, but the threading dislocations still stretched along the c-axis of the GaN layer. The use of MgO as the buffer layer decreased the surface roughness of the ZnO thin film by 58.8% due to the suppression of surface cracks through strain transfer of the sample. From deep level emission and rocking curve measurements it was found that the threading dislocations play a more important role than oxygen vacancies for high-quality ZnO thin film growth.

  5. Photoorientation in thin aligned layers of side-group liquid crystalline copolysiloxane doped with azobenzene and stilbene derivatives

    Energy Technology Data Exchange (ETDEWEB)

    Wolarz, E.; Fischer, Th.; Stumpe, J

    2003-01-31

    Optically anisotropic films of side-group liquid crystalline copolysiloxane doped with photochromic azobenzene and stilbene derivatives were prepared by using standard liquid crystal cells of 4 {mu}m in thickness. The films were irradiated with high power density laser light with the electric field vector creating an angle equal to 45 deg. with the initial optical axis of the samples. As a result of irradiation, the photoorientation of the photochromic molecules, and the cooperative reorientation of the copolysiloxane side groups occurred. In the case of the copolymer layers containing azobenzene, the optical axis was turned by an angle of 45 deg. during sufficiently long irradiation. The angle of reorientation and the degree of anisotropy were determined for the irradiated areas of the samples.

  6. Maskless texturization of phosphorus-diffused layers for crystalline Si solar cells by plasmaless dry etching with chlorine trifluoride gas

    Energy Technology Data Exchange (ETDEWEB)

    Kohata, Hayato [Department of Electrical Engineering and Electronics, Seikei University, 3-3-1 Kichijoji-Kitamachi, Musashino, Tokyo 180-8633 (Japan); Saito, Yoji [Department of Electrical Engineering and Electronics, Seikei University, 3-3-1 Kichijoji-Kitamachi, Musashino, Tokyo 180-8633 (Japan); Department of Electrical and Mechanical Engineering, Seikei University, 3-3-1 Kichijoji-Kitamachi, Musashino, Tokyo 180-8633 (Japan)

    2010-12-15

    Reflection loss of silicon solar cells can be reduced by texturing the surfaces. We investigated the texturization process for crystalline Si solar cells using chlorine trifluoride (ClF{sub 3}) gas treatments. Reflectance of textured surfaces was reduced to below 10% at the wavelength of 600 nm. However, the efficiency increase for the random-textured solar cells was below 10% and was much less than the increase for the absorbed light in the substrates after texturization. In this study, we tried to improve the electrical characteristics of textured cells by modifying the fabrication process. The diffused layers were treated with chlorine trifluoride gas to form textured structures. The reflectance of the textured surface, obtained by the maskless etching with ClF{sub 3}, was approximately 17.8% at the wavelength of 600 nm. Solar cells with textured substrates were fabricated and their improved performance was demonstrated. (author)

  7. Novel Hybrid Ablative/Ceramic Layered Composite for Earth Re-entry Thermal Protection: Microstructural and Mechanical Performance

    OpenAIRE

    Triantou, K.; Mergia, K.; Marinou, A.; Vekinis, G.; Bárcena, Jorge; Florez, S.; Perez, B.; Pinaud, G.; Bouilly, J.M.; Fischer, W.P.P.

    2015-01-01

    In view of spacecraft re-entry applications into planetary atmospheres, hybrid thermal protection systems based on layered composites of ablative materials and ceramic matrix composites are investigated. Joints of ASTERM (TM) lightweight ablative material with C-f/SiC (SICARBON (TM)) were fabricated using commercial high temperature inorganic adhesives. Sound joints without defects are produced and very good bonding of the adhesive with both base materials is observed. Mechanical shear tests ...

  8. Crystalline Molybdenum Oxide Thin-Films for Application as Interfacial Layers in Optoelectronic Devices

    DEFF Research Database (Denmark)

    Fernandes Cauduro, André Luis; dos Reis, Roberto; Chen, Gong

    2017-01-01

    The ability to control the interfacial properties in metal-oxide thin films through surface defect engineering is vital to fine-tune their optoelectronic properties and thus their integration in novel optoelectronic devices. This is exemplified in photovoltaic devices based on organic, inorganic...... with structural characterizations, this work addresses a novel method for tuning, and correlating, the optoelectronic properties and microstructure of device-relevant MoOx layers....

  9. Melt processed crystalline ceramic waste forms for advanced nuclear fuel cycles: CRP T21027 1813: Processing technologies for high level waste, formulation of matrices and characterization of waste forms, task 17208: Final report

    Energy Technology Data Exchange (ETDEWEB)

    Amoroso, J. W. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Marra, J. C. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2015-08-26

    A multi-phase ceramic waste form is being developed at the Savannah River National Laboratory (SRNL) for treatment of secondary waste streams generated by reprocessing commercial spent nuclear. The envisioned waste stream contains a mixture of transition, alkali, alkaline earth, and lanthanide metals. Ceramic waste forms are tailored (engineered) to incorporate waste components as part of their crystal structure based on knowledge from naturally found minerals containing radioactive and non-radioactive species similar to the radionuclides of concern in wastes from fuel reprocessing. The ability to tailor ceramics to mimic naturally occurring crystals substantiates the long term stability of such crystals (ceramics) over geologic timescales of interest for nuclear waste immobilization [1]. A durable multi-phase ceramic waste form tailored to incorporate all the waste components has the potential to broaden the available disposal options and thus minimize the storage and disposal costs associated with aqueous reprocessing. This report summarizes results from three years of work on the IAEA Coordinated Research Project on “Processing technologies for high level waste, formulation of matrices and characterization of waste forms” (T21027), and specific task “Melt Processed Crystalline Ceramic Waste Forms for Advanced Nuclear Fuel Cycles” (17208).

  10. Melt processed crystalline ceramic waste forms for advanced nuclear fuel cycles: CRP T21027 1813: Processing technologies for high level waste, formulation of matrices and characterization of waste forms, Task 17208: Final report

    Energy Technology Data Exchange (ETDEWEB)

    Amoroso, J. W. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Marra, J. C. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2015-08-26

    A multi-phase ceramic waste form is being developed at the Savannah River National Laboratory (SRNL) for treatment of secondary waste streams generated by reprocessing commercial spent nuclear. The envisioned waste stream contains a mixture of transition, alkali, alkaline earth, and lanthanide metals. Ceramic waste forms are tailored (engineered) to incorporate waste components as part of their crystal structure based on knowledge from naturally found minerals containing radioactive and non-radioactive species similar to the radionuclides of concern in wastes from fuel reprocessing. The ability to tailor ceramics to mimic naturally occurring crystals substantiates the long term stability of such crystals (ceramics) over geologic timescales of interest for nuclear waste immobilization [1]. A durable multi-phase ceramic waste form tailored to incorporate all the waste components has the potential to broaden the available disposal options and thus minimize the storage and disposal costs associated with aqueous reprocessing. This report summarizes results from three years of work on the IAEA Coordinated Research Project on “Processing technologies for high level waste, formulation of matrices and characterization of waste forms” (T21027), and specific task “Melt Processed Crystalline Ceramic Waste Forms for Advanced Nuclear Fuel Cycles” (17208).

  11. Crystalline boron nitride aerogels

    Science.gov (United States)

    Zettl, Alexander K.; Rousseas, Michael; Goldstein, Anna P.; Mickelson, William; Worsley, Marcus A.; Woo, Leta

    2017-04-04

    This disclosure provides methods and materials related to boron nitride aerogels. In one aspect, a material comprises an aerogel comprising boron nitride. The boron nitride has an ordered crystalline structure. The ordered crystalline structure may include atomic layers of hexagonal boron nitride lying on top of one another, with atoms contained in a first layer being superimposed on atoms contained in a second layer.

  12. Effect of Mesostructured Layer upon Crystalline Properties and Device Performance on Perovskite Solar Cells.

    Science.gov (United States)

    Listorti, Andrea; Juarez-Perez, Emilio J; Frontera, Carlos; Roiati, Vittoria; Garcia-Andrade, Laura; Colella, Silvia; Rizzo, Aurora; Ortiz, Pablo; Mora-Sero, Ivan

    2015-05-07

    One of the most fascinating characteristics of perovskite solar cells (PSCs) is the retrieved obtainment of outstanding photovoltaic (PV) performances withstanding important device configuration variations. Here we have analyzed CH3NH3PbI3-xClx in planar or in mesostructured (MS) configurations, employing both titania and alumina scaffolds, fully infiltrated with perovskite material or presenting an overstanding layer. The use of the MS scaffold induces to the perovskite different structural properties, in terms of grain size, preferential orientation, and unit cell volume, in comparison to the ones of the material grown with no constraints, as we have found out by X-ray diffraction analyses. We have studied the effect of the PSC configuration on photoinduced absorption and time-resolved photoluminescence, complementary techniques that allow studying charge photogeneration and recombination. We have estimated electron diffusion length in the considered configurations observing a decrease when the material is confined in the MS scaffold with respect to a planar architecture. However, the presence of perovskite overlayer allows an overall recovering of long diffusion lengths explaining the record PV performances obtained with a device configuration bearing both the mesostructure and a perovskite overlayer. Our results suggest that performance in devices with perovskite overlayer is mainly ruled by the overlayer, whereas the mesoporous layer influences the contact properties.

  13. Liquid crystalline nanosheet colloids with controlled particle size obtained by exfoliating single crystal of layered niobate k(4)nb(6)o(17).

    Science.gov (United States)

    Miyamoto, Nobuyoshi; Nakato, Teruyuki

    2004-05-20

    Colloidally dispersed niobate nanosheets with the thickness of 1.8 nm and controlled mean lateral sizes of 0.15-7.8 mum were prepared and their liquid crystallinity was examined. The nanosheet colloids with different lateral sizes were obtained by exfoliation of single crystals of layered niobate K4Nb6O17 and subsequent ultrasonication. Naked-eye and microscope observations of the nanosheet colloids between crossed polarizers revealed liquid crystallinity of the sols characterized by birefringence as functions of the lateral sizes and concentration of the nanosheets. The nanosheet colloids with smaller lateral sizes (0.15-1.9 mum) varied from isotropic to biphasic (isotropic + liquid crystalline), and finally to fully liquid crystalline states as the colloid concentration increased. The phase transition concentrations (from isotropic to biphasic and biphasic to liquid crystalline) decreased with increasing aspect ratio (lateral-to-thickness ratio) of the nanosheets, almost in accordance with the prediction by Onsager theory, indicating that the liquid crystallinity is explained basically by excluded-volume effect between the nanosheets. On the other hand, the colloids with larger lateral sizes (6.2 and 7.8 mum) stably kept liquid crystalline state even at very low concentration (5.1 x 10-6 in volume fraction), which was much lower than that expected from the theory.

  14. 3D spin-flop transition in enhanced 2D layered structure single crystalline TlCo2Se2

    Science.gov (United States)

    Jin, Z.; Xia, Z.-C.; Wei, M.; Yang, J.-H.; Chen, B.; Huang, S.; Shang, C.; Wu, H.; Zhang, X.-X.; Huang, J.-W.; Ouyang, Z.-W.

    2016-10-01

    The enhanced 2D layered structure single crystalline TlCo2Se2 has been successfully fabricated, which exhibits field-induced 3D spin-flop phase transitions. In the case of the magnetic field parallel to the c-axis (B//c), the applied magnetic field induces the evolution of the noncollinear helical magnetic coupling into a ferromagnetic (FM) state with all the magnetization of the Co ion parallel to the c-axis. A striking variation of the field-induced strain within the ab-plane is noticed in the magnetic field region of 20-30 T. In the case of the magnetic field perpendicular to the c-axis (B  ⊥  c), the inter-layer helical antiferromagnetic (AFM) coupling may transform to an initial canted AFM coupling, and then part of it transforms to an intermediate metamagnetic phase with the alignment of two-up-one-down Co magnetic moments and finally to an ultimate FM coupling in higher magnetic fields. The robust noncollinear AFM magnetic coupling is completely destroyed above 30 T. In combination with the measurements of magnetization, magnetoresistance and field-induced strain, a complete magnetic phase diagram of the TlCo2Se2 single crystal has been depicted, demonstrating complex magnetic structures even though the crystal geometry itself gives no indication of the magnetic frustration.

  15. Influence of SiO{sub 2} buffer layer on the crystalline quality and photoluminescence of ZnO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Xu, L H; Chen, Y L; Xu, F [College of Math and Physics, Nanjing University of Information Science and Technology, Nanjing, 210044 (China); Li, X Y [Department of Applied Physics, Nanjing University of Science and Technology, Nanjing, 210094 (China); Hua, S, E-mail: congyu3256@sina.com [Institute of Electronic Engineering and Photoelectric Technology, Nanjing University of Science and Technology, Nanjing, 210094 (China)

    2011-02-01

    In this work, a SiO{sub 2} buffer layer was first grown on Si substrate by thermal oxidation, and then ZnO thin films were deposited on SiO{sub 2} buffer layer and Si substrate by electron beam evaporation and sol-gel method. The influence of SiO{sub 2} buffer layer on the crystalline quality and photoluminescence of the films was investigated. The analyses of X-ray diffraction (XRD) showed that all the ZnO thin films had a hexagonal wurtzite structure and were preferentially oriented along the c-axis perpendicular to the substrate surface. The SiO{sub 2} buffer layer improved the crystalline quality and decreased the stress in ZnO thin films. The surface morphology analyses of the samples indicated that ZnO thin films deposited on SiO{sub 2} buffer layers had densely packed grains which obviously increased compared with those grown on bare Si substrate. The photoluminescence spectra of the samples showed that the ZnO thin films deposited on SiO{sub 2} buffer layers had stronger ultraviolet emission performance. The results suggest that SiO{sub 2} buffer layer can improve the crystalline quality and ultraviolet emission of ZnO thin films.

  16. 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)

  17. TEM observation and study of three-layer Al2O3/ZrO2 ceramics.

    Science.gov (United States)

    Chen, Bei; Cheng, Chuan; Chen, Bin

    2010-03-01

    The micrograph and the crystal orientation relationship of Al2O3/ZrO2 laminated ceramics were studied with the help of transmission electronic microscope (TEM). The experiment results showed that: the Al2O3 and ZrO2 grain sizes were small and the links among the crystals were good. No flaws such as pores or micro-cracks were observed in the micro-structure. Further TEM analyses and electronic diffraction spot calculation proved that interface compressive stress could greatly restrain the transformation of the tetragonal phase and increase the contents of transformable tetragon, but did not change the orientation relation between the tetragonal and monoclinic phase, while (100),m//(010), still exist in the three-layer ZrO2 ceramics.

  18. Low-Temperature Atomic Layer Deposition of Crystalline and Photoactive Ultrathin Hematite Films for Solar Water Splitting.

    Science.gov (United States)

    Steier, Ludmilla; Luo, Jingshan; Schreier, Marcel; Mayer, Matthew T; Sajavaara, Timo; Grätzel, Michael

    2015-12-22

    We developed a low-temperature atomic layer deposition route to deposit phase pure and crystalline hematite (α-Fe2O3) films at 230 °C without the need for postannealing. Homogenous and conformal deposition with good aspect ratio coverage was demonstrated on a nanostructured substrate and analyzed by transmission electron microscopy. These as-deposited α-Fe2O3 films were investigated as photoanodes for photoelectrochemical water oxidation and found to be highly photoactive. Combined with a TiO2 underlayer and a low-cost Ni(OH)2 catalyst, hematite films of less than 10 nm in thickness reached photocurrent densities of 0.3 mA cm(-2) at 1.23 V vs RHE and a photocurrent onset potential of less than 0.9 V vs RHE, previously unseen for films this thin and without high temperature annealing. In a thickness-dependent photoelectrochemical analysis, we identified a hematite thickness of only 10 nm to yield the highest internal quantum efficiency when using a suitable underlayer such as TiO2 that induces doping of the hematite film and reduces electron/hole recombination at the back contact. We find that, at high bias potentials, photocurrent density and quantum efficiency proportionally increase with light absorption in films thinner than 10 nm and are limited by the space charge layer width in thicker films. Thus, we propose to apply hematite films of 10 nm in thickness for future developments on suitable nanostructured conductive scaffolds that can now be extended to organic scaffolds due to our low-temperature process.

  19. Highly efficient hydrogen evolution reaction using crystalline layered three-dimensional molybdenum disulfides grown on graphene film.

    Energy Technology Data Exchange (ETDEWEB)

    Behranginia, Amirhossein; Asadi, Mohammad; Liu, Cong; Yasaei, Poya; Kumar, Bijandra; Phillips, Patrick; Foroozan, Tara; Waranius, Joseph C.; Kim, Kibum; Abiade, Jeremiah; Klie, Robert F.; Curtiss, Larry A.; Salehi-Khojin, Amin

    2016-01-26

    Electrochemistry is central to applications in the field of energy storage and generation. However, it has advanced far more slowly over the last two decades, mainly because of a lack of suitable and affordable catalysts. Here, we report the synthesis of highly crystalline layered three-dimensional (3D) molybdenum disulfide (MoS2) catalysts with bare Mo-edge atoms and demonstrate their remarkable performance for the hydrogen evolution reaction (HER). We found that Mo-edge-terminated 3D MoS2 directly grown on graphene film exhibits a remarkable exchange current density (18.2 mu A cm(-2)) and turnover frequency (>4 S-1) for HER. The obtained exchange current density is 15.2 and 2.3 times higher than that of MoS2/graphene and MoS2/Au catalysts, respectively, both with sulfided Mo-edge atoms. An easily scalable and robust growth process on a wide variety of substrates, along with prolonged stability, suggests that this material is a promising catalyst in energy-related applications.

  20. A low-crystalline ruthenium nano-layer supported on praseodymium oxide as an active catalyst for ammonia synthesis.

    Science.gov (United States)

    Sato, Katsutoshi; Imamura, Kazuya; Kawano, Yukiko; Miyahara, Shin-Ichiro; Yamamoto, Tomokazu; Matsumura, Syo; Nagaoka, Katsutoshi

    2017-01-01

    Ammonia is a crucial chemical feedstock for fertilizer production and is a potential energy carrier. However, the current method of synthesizing ammonia, the Haber-Bosch process, consumes a great deal of energy. To reduce energy consumption, a process and a substance that can catalyze ammonia synthesis under mild conditions (low temperature and low pressure) are strongly needed. Here we show that Ru/Pr2O3 without any dopant catalyzes ammonia synthesis under mild conditions at 1.8 times the rates reported with other highly active catalysts. Scanning transmission electron micrograph observations and energy dispersive X-ray analyses revealed the formation of low-crystalline nano-layers of ruthenium on the surface of Pr2O3. Furthermore, CO2 temperature-programmed desorption revealed that the catalyst was strongly basic. These unique structural and electronic characteristics are considered to synergistically accelerate the rate-determining step of NH3 synthesis, cleavage of the N 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000

  1. Flash Memory Featuring Low-Voltage Operation by Crystalline ZrTiO4 Charge-Trapping Layer

    Science.gov (United States)

    Shen, Yung-Shao; Chen, Kuen-Yi; Chen, Po-Chun; Chen, Teng-Chuan; Wu, Yung-Hsien

    2017-03-01

    Crystalline ZrTiO4 (ZTO) in orthorhombic phase with different plasma treatments was explored as the charge-trapping layer for low-voltage operation flash memory. For ZTO without any plasma treatment, even with a high k value of 45.2, it almost cannot store charges due the oxygen vacancies-induced shallow-level traps that make charges easy to tunnel back to Si substrate. With CF4 plasma treatment, charge storage is still not improved even though incorporated F atoms could introduce additional traps since the F atoms disappear during the subsequent thermal annealing. On the contrary, nevertheless the k value degrades to 40.8, N2O plasma-treated ZTO shows promising performance in terms of 5-V hysteresis memory window by ±7-V sweeping voltage, 2.8-V flatband voltage shift by programming at +7 V for 100 μs, negligible memory window degradation with 105 program/erase cycles and 81.8% charge retention after 104 sec at 125 °C. These desirable characteristics are ascribed not only to passivation of oxygen vacancies-related shallow-level traps but to introduction of a large amount of deep-level bulk charge traps which have been proven by confirming thermally excited process as the charge loss mechanism and identifying traps located at energy level beneath ZTO conduction band by 0.84 eV~1.03 eV.

  2. Investigation of charges carrier density in phosphorus and boron doped SiN{sub x}:H layers for crystalline silicon solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Paviet-Salomon, B., E-mail: bertrand.paviet-salomon@epfl.ch [Commissariat à l’Énergie Atomique (CEA), Laboratoire d’Innovation pour les Technologies des Énergies Nouvelles et les nanomatériaux (LITEN), Institut National de l’Énergie Solaire - INES, 50 avenue du Lac Léman, 73377 Le Bourget du Lac (France); Gall, S. [Commissariat à l’Énergie Atomique (CEA), Laboratoire d’Innovation pour les Technologies des Énergies Nouvelles et les nanomatériaux (LITEN), Institut National de l’Énergie Solaire - INES, 50 avenue du Lac Léman, 73377 Le Bourget du Lac (France); Slaoui, A. [Institut de l’Électronique du Solide et des Systèmes (InESS), Unité Mixte de Recherche 7163 Centre National de la Recherche Scientifique-Université de Strasbourg (UMR 7163 CNRS-UDS), 23 rue du Loess, BP 20 CR, 67037 Strasbourg (France)

    2013-05-15

    Highlights: ► We investigate the properties of phosphorus and boron-doped silicon nitride films. ► Phosphorus-doped layers yield higher lifetimes than undoped ones. ► The fixed charges density decreases when increasing the films phosphorus content. ► Boron-doped films feature very low lifetimes. ► These doped layers are of particular interest for crystalline silicon solar cells. -- Abstract: Dielectric layers are of major importance in crystalline silicon solar cells processing, especially as anti-reflection coatings and for surface passivation purposes. In this paper we investigate the fixed charge densities (Q{sub fix}) and the effective lifetimes (τ{sub eff}) of phosphorus (P) and boron (B) doped silicon nitride layers deposited by plasma-enhanced chemical vapour deposition. P-doped layers exhibit a higher τ{sub eff} than standard undoped layers. In contrast, B-doped layers exhibit lower τ{sub eff}. A strong Q{sub fix} decrease is to be seen when increasing the P content within the film. Based on numerical simulations we also demonstrate that the passivation obtained with P- and B-doped layers are limited by the interface states rather than by the fixed charges.

  3. Effects of initial layers on surface roughness and crystallinity of microcrystalline silicon thin films formed by remote electron cyclotron resonance silane plasma

    CERN Document Server

    Murata, K; Hori, Masaki; Goto, T; Ito, M

    2002-01-01

    We have observed mu c-Si:H films grown in the glass substrate in electron cyclotron resonance plasma-enhanced chemical vapor deposition employing two-step growth (TSG) method, where the seed layer was formed without charged species firstly, and subsequently, the film with charged species. The mu c-Si:H films with smooth surface and high crystallinity were synthesized with a relatively high deposition rate at a low substrate temperature by TSG. By Fourier transform infrared attenuated-total reflection, it was found that the surface roughness and crystallinity of seed layer were related to the ratio of SiH bonds over SiH sub 2 ones in the film. Consequently, the control of chemical bonds at the initial layer is of importance and TSG method is effective for the formation of mu c-Si:H film with high quality.

  4. Cake layers and long filtration times protect ceramic micro-filtration membranes for fouling

    NARCIS (Netherlands)

    Lu, J.

    2013-01-01

    The objective of this research was to decrease membrane fouling of a ceramic microfiltration system and at the same time increase the recovery. A conventional operation in micro- and ultrafiltration is an in-line coagulation and a frequent hydraulic backwash. The idea about these frequent backwashes

  5. Influence of thermal expansion mismatch on residual stress profile in veneering ceramic layered on zirconia: Measurement by hole-drilling.

    Science.gov (United States)

    Mainjot, Amélie K; Najjar, Achref; Jakubowicz-Kohen, Boris D; Sadoun, Michaël J

    2015-09-01

    Mismatch in thermal expansion coefficient between core and veneering ceramic (Δα=αcore-αveneer, ppm/°C) is reported as a crucial parameter influencing veneer fractures with Yttria-tetragonal-zirconia-polycrystal (Y-TZP) prostheses, which still constitutes a misunderstood problem. However, the common positive Δα concept remains empirical. The objective of this study is to investigate the Δα dependence of residual stress profiles in veneering ceramic layered on Y-TZP frameworks. The stress profile was measured with the hole-drilling method in bilayered disc samples of 20mm diameter with a 0.7mm thick Y-TZP framework and a 1.5mm thick veneer layer. 3 commercial and 4 experimental veneering ceramics (n=3 per group) were used to obtain different Δα varying from -1.3ppm/°C to +3.2ppm/°C, which were determined by dilatometric analyses. Veneer fractures were observed in samples with Δα≥+2.3 or ≤-0.3ppm/°C. Residual stress profiles measured in other groups showed compressive stresses in the surface, these stresses decreasing with depth and then becoming more compressive again near the interface. Small Δα variations were shown to induce significant changes in residual stress profiles. Compressive stress near the framework was found to decrease inversely to Δα. Veneer CTE close to Y-TZP (+0.2ppm/°C Δα) gived the most favorable stress profile. Yet, near the framework, Δα-induced residual stress varied inversely to predictions. This could be explained by the hypothesis of structural changes occurrence within the Y-TZP surface. Consequently, the optimum Δα value cannot be determined before understanding Y-TZP's particular behavior when veneered. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  6. Electromagnetic interference shielding performance of nano-layered Ti3SiC2 ceramics at high-temperatures

    Directory of Open Access Journals (Sweden)

    Sigong Li

    2018-01-01

    Full Text Available The X-band electromagnetic interference (EMI shielding properties of nano-layered Ti3SiC2 ceramics were evaluated from room temperature up to 800°C in order to explore the feasibility of Ti3SiC2 as efficient high temperature EMI shielding material. It was found that Ti3SiC2 exhibits satisfactory EMI shielding effectiveness (SE close to 30 dB at room temperature and the EMI SE shows good temperature stability. The remarkable EMI shielding properties of Ti3SiC2 can be mainly attributed to high electrical conductivity, high dielectric loss and more importantly the multiple reflections due to the layered structure.

  7. Novel Hybrid Ablative/Ceramic Layered Composite for Earth Re-entry Thermal Protection: Microstructural and Mechanical Performance

    Science.gov (United States)

    Triantou, K.; Mergia, K.; Marinou, A.; Vekinis, G.; Barcena, J.; Florez, S.; Perez, B.; Pinaud, G.; Bouilly, J.-M.; Fischer, W. P. P.

    2015-04-01

    In view of spacecraft re-entry applications into planetary atmospheres, hybrid thermal protection systems based on layered composites of ablative materials and ceramic matrix composites are investigated. Joints of ASTERM™ lightweight ablative material with Cf/SiC (SICARBON™) were fabricated using commercial high temperature inorganic adhesives. Sound joints without defects are produced and very good bonding of the adhesive with both base materials is observed. Mechanical shear tests under ambient conditions and in liquid nitrogen show that mechanical failure always takes place inside the ablative material with no decohesion of the interface of the adhesive layer with the bonded materials. Surface treatment of the ablative surface prior to bonding enhances both the shear strength and the ultimate shear strain by up to about 60%.

  8. New class of Si-based superlattices - Alternating layers of crystalline Si and porous amorphous Si(1-x)Ge(x) alloys

    Science.gov (United States)

    Fathauer, R. W.; George, T.; Jones, E. W.; Pike, W. T.; Ksendzov, A.; Vasquez, R. P.

    1992-01-01

    Superlattices consisting of alternating layers of crystalline Si and porous amorphous Si(1-x)Ge(x) have been fabricated. This is accomplished by first growing a Si/Si(0.7)Ge(0.3) superlattice by molecular beam epitaxy, followed by Ar-ion milling to form mesa structures, and finally by immersion in HF:HNO3:H2O. This solution creates a porous structure similar to that created by anodic etching, and a high selectivity is observed for the conversion of the alloy layers relative to the Si layers. The degree of selectivity is found to depend on alloy-layer thickness and strain. Superlattices have been fabricated from 1-micron wide mesas with Si(0.7)Ge(0.3) layers fully converted to 5-nm thick porous amorphous material.

  9. Enhancing Lifetime and Efficiency of Organic Solar Cell by Applying an In Situ Synthesized Low-Crystalline ZnO Layer.

    Science.gov (United States)

    Arabpour Roghabadi, Farzaneh; Ahmadi, Vahid; Abdollahi Nejand, Bahram; Oniy Aghmiuni, Karim

    2017-06-09

    By introducing an in situ synthesized low-crystalline ZnO (LC-ZnO) (amorphous) layer between the cathode and the active layer of PCPDTBT:CdSe solar cell {PCPDTBT: poly[2,6-(4,4-bis(2-ethylhexyl)-4H-cyclopenta [2,1-b:3,4-b']dithiophene)-alt-4,7(2,1,3-benzothiadiazole)]}, the device keeps more than 80 and 40 % of its initial lifetime after 180 and 360 days without any encapsulation, respectively. In this regard, 180 days is the highest lifetime achieved for polymer-based solar cells with direct configuration. In addition, the power conversion efficiency (PCE) is improved up to 70 % in the presence of the LC-ZnO interfacial layer. The LC-ZnO layer is synthesized during polymer annealing after solution-deposition of the precursor at a low temperature (140 °C) and a short time. Highly crystalline ZnO (HC-ZnO) nanoparticles are also synthesized and applied as an interfacial layer. The results show that the LC-ZnO is superior to the HC-ZnO in acting as cathode interfacial layer and moisture scavenger because of the high coverage and surface area provided by the in situ synthesis method. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Growth of novel ceramic layers on metals via chemical and heat treatments for inducing various biological functions

    Directory of Open Access Journals (Sweden)

    Tadashi eKokubo

    2015-10-01

    Full Text Available The present authors’ systematic studies on growth of novel ceramic layers on Ti metal and its alloys by chemical and heat treatments for inducing bone-bonding bioactivity and some other biological functions are reviewed. Ti metal formed an apatite on its surface in a simulated body fluid (SBF, when heat-treated after exposure to strong acid solutions to form rutile surface layer, or to strong alkali solutions to form sodium titanate surface layer. Both types of Ti metal tightly bonded to the living bone.The alkali and heat treatment was applied to the surface Ti metal of an artificial hip joint and successfully used in the clinic since 2007. The acid and heat treatments was applied to porous Ti metal to induce osteoconductivity as well as osteoinductivity. The resulting product was successfully used in clinical trials for spinal fusion devices. For the Ti-based alloys, the alkali and heat treatment was a little modified to form calcium titanate surface layer. Bone-growth promoting Mg, Sr, and Zn ions as well as the antibacterial Ag ion were successfully incorporated into the calcium titanate layer.

  11. Electrical and ferroelectric studies of the 2-layered SrBi{sub 2}Ta{sub 2}O{sub 9} based ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Swain, Sridevi [Department of Physics & Astronomy, National Institute of Technology, Rourkela 769008 (India); Kumar, Pawan, E-mail: pawankumar@nitrkl.ac.in [Department of Physics & Astronomy, National Institute of Technology, Rourkela 769008 (India); Choudhary, Ram Bilash [Department of Applied Physics, Indian School of Mines, Dhanbad 826004 (India)

    2015-11-15

    SrBi{sub 2}Ta{sub 2}O{sub 9}/SBT, Sr{sub 0.8}Bi{sub 2.15}Ta{sub 2}O{sub 9}/SB{sub ex}T and SrBi{sub 2}(Ta{sub 0.925}W{sub 0.075}){sub 2}O{sub 9}/SBTW, 2-layered perovskite ferroelectric ceramic samples were prepared in single phase by solid-state reaction technique. Similar crystal structure was observed from the XRD study of the calcined powders of all the SBT based systems. Enhanced transition temperature (T{sub c}), dielectric constant (ε{sub r}) and ferroelectric properties were observed in both the SB{sub ex}T and SBTW ceramic samples compared to the pure SBT ceramic samples. The higher remnant polarization (P{sub r})~8.07 μC/cm{sup 2} and lower coercive field (E{sub c})~15.18 kV/cm were observed in the SB{sub ex}T ceramic samples. The bipolar fatigue study was carried out and the normalized polarization vs. number of cycles (up to 10{sup 9}) behavior confirmed the fatigue resistant nature of all the SBT based ceramic samples. In comparison to the pure SBT ceramic samples, decreased leakage current with increased piezoelectric properties were observed in both the SB{sub ex}T and SBTW ceramic samples.

  12. Low cost sol–gel derived SiC–SiO{sub 2} nanocomposite as anti reflection layer for enhanced performance of crystalline silicon solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Jannat, Azmira [School of Semiconductor and Chemical Engineering, Solar Energy Research Center, Chonbuk National University, Jeonju, Jeonbuk 54896 (Korea, Republic of); Solar Energy Engineering, Chonbuk National University, Jeonju, Jeonbuk 54896 (Korea, Republic of); Lee, Woojin [School of Semiconductor and Chemical Engineering, Solar Energy Research Center, Chonbuk National University, Jeonju, Jeonbuk 54896 (Korea, Republic of); Akhtar, M. Shaheer, E-mail: shaheerakhtar@jbnu.ac.kr [School of Semiconductor and Chemical Engineering, Solar Energy Research Center, Chonbuk National University, Jeonju, Jeonbuk 54896 (Korea, Republic of); New & Renewable Energy Materials Development Center (NewREC), Chonbuk National University, Jeonbuk (Korea, Republic of); Li, Zhen Yu [School of Semiconductor and Chemical Engineering, Solar Energy Research Center, Chonbuk National University, Jeonju, Jeonbuk 54896 (Korea, Republic of); Yang, O.-Bong, E-mail: obyang@jbnu.ac.kr [School of Semiconductor and Chemical Engineering, Solar Energy Research Center, Chonbuk National University, Jeonju, Jeonbuk 54896 (Korea, Republic of); New & Renewable Energy Materials Development Center (NewREC), Chonbuk National University, Jeonbuk (Korea, Republic of)

    2016-04-30

    Graphical abstract: - Highlights: • Sol–gel derived SiC–SiO{sub 2} nanocomposite was prepared. • It effectively coated as AR layer on p-type Si-wafer. • SiC–SiO{sub 2} layer on Si solar cells exhibited relatively low reflectance of 7.08%. • Fabricated Si solar cell attained highly comparable performance of 16.99% to commercial device. - Abstract: This paper describes the preparation, characterizations and the antireflection (AR) coating application in crystalline silicon solar cells of sol–gel derived SiC–SiO{sub 2} nanocomposite. The prepared SiC–SiO{sub 2} nanocomposite was effectively applied as AR layer on p-type Si-wafer via two step processes, where the sol–gel of precursor solution was first coated on p-type Si-wafer using spin coating at 2000 rpm and then subjected to annealing at 450 °C for 1 h. The crystalline, and structural observations revealed the existence of SiC and SiO{sub 2} phases, which noticeably confirmed the formation of SiC–SiO{sub 2} nanocomposite. The SiC–SiO{sub 2} layer on Si solar cells was found to be an excellent AR coating, exhibiting the low reflectance of 7.08% at wavelengths ranging from 400 to 1000 nm. The fabricated crystalline Si solar cell with SiC–SiO{sub 2} nanocomposite AR coating showed comparable power conversion efficiency of 16.99% to the conventional Si{sub x}N{sub x} AR coated Si solar cell. New and effective sol–gel derived SiC–SiO{sub 2} AR layer would offer a promising technique to produce high performance Si solar cells with low-cost.

  13. Bioactive glass ceramics: properties and applications.

    Science.gov (United States)

    Kokubo, T

    1991-03-01

    Heat treatment of an MgO-CaO-SiO2-P2O5 glass gave a glass ceramic containing crystalline apatite (Ca10(PO4)6O,F2] and beta-wollastonite (CaO,SiO2) in an MgO-CaO-SiO2 glassy matrix. It showed bioactivity and a fairly high mechanical strength which decreased only slowly, even under load-bearing conditions in the body. It is used clinically as artificial vertebrae, iliac bones, etc. The bioactivity of this glass ceramic was attributed to apatite formation on its surface in the body. Dissolution of calcium and silicate ions from the glass ceramic was considered to play an important role in forming the surface apatite layer. It was shown that some new kinds of bioactive materials can be developed from CaO,SiO2-based glasses. Ceramics, metals and organic polymers coated with bone-like apatite were obtained when such materials were placed in the vicinity of a CaO,SiO2-based glass in a simulated body fluid. A bioactive bone cement which was hardened within 4 min and bonded to living bone, forming an apatite, was obtained by mixing a CaO,SiO2-based glass powder with a neutral ammonium phosphate solution. Its compressive strength reached 80 MPa comparable to that of poly(methyl methacrylate) within 3 d. A bioactive and ferromagnetic glass ceramic containing crystalline magnetite (Fe3O4) in a matrix of CaO,SiO2-based glassy and crystalline phases was obtained by a heat treatment of a Fe2O3-CaO.SiO2-B2O3-P2O5 glass. This glass ceramic was shown to be useful as thermoseeds for hyperthermia treatment of cancer.

  14. Biosorption of uranium and copper by Bacillus Sphaericus JG-A12 cells, spores and S-layer proteins embedded in sol-gel ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Raff, J.; Soltmann, U.; Boettcher, H. [Arbeitsgruppe Funktionelle Schichten, GMBU e.V., Dresden (Germany); Matys, S.; Pompe, W. [Inst. fuer Materialwissenschaft, Technische Univ. Dresden (Germany); Selenska-Pobell, S.

    2002-05-01

    Vegetative cells, spores and stabilized S-layer sheets of B. sphaericus JG-A12 were embedded in SiO{sub 2} bulk particles using sol-gel techniques. In sorption experiments the metal binding capacity of the free biocomponents and the corresponding biological ceramics were compared. (orig.)

  15. Three-unit posterior zirconia-ceramic fixed dental prostheses (FDPs) veneered with layered and milled (CAD-on) veneering ceramics: 1-year follow-up of a randomized controlled clinical trial.

    Science.gov (United States)

    Grohmann, Philipp; Bindl, Andreas; Hämmerle, Christoph; Mehl, Albert; Sailer, Irena

    2015-01-01

    The aim of this multicenter randomized controlled clinical trial was to test posterior zirconia-ceramic fixed dental prostheses (FDPs) veneered with a computer-aided design/computer- assisted manufacture (CAD/CAM) lithium disilicate veneering ceramic (CAD-on) and manually layered zirconia veneering ceramic with respect to survival of the FDPs, and technical and biologic outcomes. Sixty patients in need of one posterior three-unit FDP were included. The zirconia frameworks were produced with a CAD/CAM system (Cerec inLab 3D/Cerec inEOS inLab). Thirty FDPs were veneered with a CAD/CAM lithium disilicate veneering ceramic (Cad-on) (test) and 30 were veneered with a layered zirconia veneering ceramic (control). For the clinical evaluation at baseline, 6, and 12 months, the United States Public Health Service (USPHS) criteria were used. The biologic outcome was judged by comparing the plaque control record (PCR), bleeding on probing (BOP), and probing pocket depth (PPD). Data were statistically analyzed. Fifty-six patients were examined at a mean follow-up of 13.9 months. At the 1-year follow-up the survival rate was 100% in the test and in the control group. No significant differences of the technical outcomes occurred. Major chipping occurred in the control group (n = 3) and predominantly minor chipping in the test group (minor n = 2, major n = 1). No biologic problems or differences were found. Both types of zirconia-ceramic FDPs exhibited very good clinical outcomes without differences between groups. Chipping occurred in both types of FDPs at small amounts, yet the extension of the chippings differed. The test FDPs predominantly exhibited minor chipping, the control FDPs major chipping.

  16. Characterization of crystallinity of Ge{sub 1−x}Sn{sub x} epitaxial layers grown using metal-organic chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Inuzuka, Yuki [Department of Crystalline Materials Science, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Ike, Shinichi; Asano, Takanori [Department of Crystalline Materials Science, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Japan Society for the Promotion of Science, Chiyoda-ku, Tokyo 102-8472 (Japan); Takeuchi, Wakana [Department of Crystalline Materials Science, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Nakatsuka, Osamu, E-mail: nakatuka@alice.xtal.nagoya-u.ac.jp [Department of Crystalline Materials Science, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Zaima, Shigeaki [Department of Crystalline Materials Science, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); EcoTopia Science Institute, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan)

    2016-03-01

    The epitaxial growth of a Ge{sub 1−x}Sn{sub x} layer was examined using metal-organic chemical vapor deposition (MOCVD) with two types of Ge precursors; tetra-ethyl-germane (TEGe) and tertiary-butyl-germane (TBGe); and the Sn precursor tri-butyl-vinyl-tin (TBVSn). Though the growth of a Ge{sub 1−x}Sn{sub x} layer on a Ge(001) substrate by MOCVD has been reported, a high-Sn-content Ge{sub 1−x}Sn{sub x} layer and the exploration of MO material combinations for Ge{sub 1−x}Sn{sub x} growth have not been reported. Therefore, the epitaxial growth of a Ge{sub 1−x}Sn{sub x} layer on Ge(001) and Si(001) substrates was examined using these precursors. The Ge{sub 1−x}Sn{sub x} layers were pseudomorphically grown on a Ge(001) substrate, while the Ge{sub 1−x}Sn{sub x} layer with a high degree of strain relaxation was obtained on a Si(001) substrate. Additionally, it was found that the two Ge precursors have different growth temperature ranges, where the TBGe could realize a higher growth rate at a lower growth temperature than the TEGe. The Ge{sub 1−x}Sn{sub x} layers grown using a combination of TBGe and TBVSn exhibited a higher crystalline quality and a smoother surface compared with the Ge{sub 1−x}Sn{sub x} layer prepared by low-temperature molecular beam epitaxy. In this study, a Ge{sub 1−x}Sn{sub x} epitaxial layer with a Sn content as high as 5.1% on a Ge(001) substrate was achieved by MOCVD at 300 °C. - Highlights: • Tertiary-butyl-germane and tri-butyl-vinyl-tin are suitable for Ge{sub 1−x}Sn{sub x} MOCVD growth. • We achieved a Sn content of 5.1% in Ge{sub 1−x}Sn{sub x} epitaxial layer on Ge(001). • The Ge{sub 1−x}Sn{sub x} layers grown on Ge and Si by MOCVD have high crystalline quality.

  17. Long-term Bond Strength between Layering Indirect Composite Material and Zirconia Coated with Silicabased Ceramics.

    Science.gov (United States)

    Fushiki, Ryosuke; Komine, Futoshi; Honda, Junichi; Kamio, Shingo; Blatz, Markus B; Matsumura, Hideo

    2015-06-01

    This study evaluated the long-term shear bond strength between an indirect composite material and a zirconia framework coated with silica-based ceramics, taking the effect of different primers into account. A total of 165 airborne-particle abraded zirconia disks were subjected to one of three pretreatments: no pretreatment (ZR-AB), airborne-particle abrasion of zirconia coated with feldspathic porcelain (ZR-PO-AB), and 9.5% hydrofluoric acid etching of zirconia coated with feldspathic porcelain (ZR-PO-HF). An indirect composite material (Estenia C&B) was then bonded to the zirconia disks after they were treated with one of the following primers: Clearfil Photo Bond (CPB), Clearfil Photo Bond with Clearfil Porcelain Bond Activator (CPB + Activator), Estenia Opaque Primer (EOP), Porcelain Liner M Liquid B (PLB), or no priming (CON, control group). Shear bond strength was tested after 100,000 thermocycles, and the data were analyzed using the Steel-Dwass U-test (α = 0.05). For ZR-PO-AB and ZR-PO-HF specimens, bond strength was highest in the CPB+Activator group (25.8 MPa and 22.4 MPa, respectively). Bond strengths were significantly lower for ZR-AB specimens in the CON and PLB groups and for ZR-PO-AB specimens in the CON, CPB, and EOP groups. Combined application of a hydrophobic phosphate monomer (MDP) and silane coupling agent enhanced the long-term bond strength of indirect composite material to a zirconia coated with silica-based ceramics.

  18. Observation by conductive-probe atomic force microscopy of strongly inverted surface layers at the hydrogenated amorphous silicon/crystalline silicon heterojunctions

    Science.gov (United States)

    Maslova, O. A.; Alvarez, J.; Gushina, E. V.; Favre, W.; Gueunier-Farret, M. E.; Gudovskikh, A. S.; Ankudinov, A. V.; Terukov, E. I.; Kleider, J. P.

    2010-12-01

    Heterojunctions made of hydrogenated amorphous silicon (a-Si:H) and crystalline silicon (c-Si) are examined by conducting probe atomic force microscopy. Conductive channels at both (n )a-Si:H/(p)c-Si and (p)a-Si:H/(n)c-Si interfaces are clearly revealed. These are attributed to two-dimension electron and hole gases due to strong inversion layers at the c-Si surface in agreement with previous planar conductance measurements. The presence of a hole gas in (p )a-Si:H/(n)c-Si structures implies a quite large valence band offset (EVc-Si-EVa-Si:H>0.25 eV).

  19. Monolithic and bi-layer CAD/CAM lithium-disilicate versus metal-ceramic fixed dental prostheses: comparison of fracture loads and failure modes after fatigue.

    Science.gov (United States)

    Schultheis, Stefan; Strub, Joerg R; Gerds, Thomas A; Guess, Petra C

    2013-06-01

    The authors analyzed the effect of fatigue on the survival rate and fracture load of monolithic and bi-layer CAD/CAM lithium-disilicate posterior three-unit fixed dental prostheses (FDPs) in comparison to the metal-ceramic gold standard. The authors divided 96 human premolars and molars into three equal groups. Lithium-disilicate ceramic (IPS-e.max-CAD) was milled with the CEREC-3-system in full-anatomic FDP dimensions (monolithic: M-LiCAD) or as framework (Bi-layer: BL-LiCAD) with subsequent hand-layer veneering. Metal-ceramic FDPs (MC) served as control. Single-load-to-failure tests were performed before and after mouth-motion fatigue. No fracture failures occurred during fatigue. Median fracture loads in [N], before and after fatigue were, respectively, as follows: M-LiCAD, 1,298/1,900; BL-LiCAD, 817/699; MC, 1,966/1,818. M-LiCAD and MC FPDs revealed comparable fracture loads and were both significantly higher than BL-LiCAD. M-LiCAD and BL-LiCAD both failed from core/veneer bulk fracture within the connector area. MC failures were limited to ceramic veneer fractures exposing the metal core. Fatigue had no significant effect on any group. Posterior monolithic CAD/CAM fabricated lithium-disilicate FPDs were shown to be fracture resistant with failure load results comparable to the metal-ceramic gold standard. Clinical investigations are needed to confirm these promising laboratory results. Monolithic CAD/CAM fabricated lithium-disilicate FDPs appeared to be a reliable treatment alternative for the posterior load-bearing area, whereas FDPs in bi-layer configuration were susceptible to low load fracture failure.

  20. Development of Nano-crystalline Doped-Ceramic Enabled Fiber Sensors for High Temperature In-Situ Monitoring of Fossil Fuel Gases

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Hai [Missouri Univ. of Science and Technology, Rolla, MO (United States); Dong, Junhang [Univ. of Cincinnati, OH (United States); Lin, Jerry [Arizona State Univ., Tempe, AZ (United States); Romero, Van [New Mexico Institute of Mining and Technology, Socorro, NM (United States)

    2012-03-01

    This is a final technical report for the first project year from July 1, 2005 to Jan 31, 2012 for DoE/NETL funded project DE-FC26-05NT42439: Development of Nanocrystalline Doped-Ceramic Enabled Fiber Sensors for High Temperature In-Situ Monitoring of Fossil Fuel Gases. This report summarizes the technical progresses and achievements towards the development of novel nanocrystalline doped ceramic material-enabled optical fiber sensors for in situ and real time monitoring the gas composition of flue or hot gas streams involved in fossil-fuel based power generation and hydrogen production.

  1. Microstructural characterization of alumina-zirconia layered ceramics using positron annihilation spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Parente, P., E-mail: pparente@fis.uc3m.es [Departamento de Fisica, Universidad Carlos III de Madrid, 28911 Leganes (Spain); Ortega, Y. [Departamento de Fisica de Materiales, Facultad de Ciencias Fisicas, Univ. Complutense de Madrid, 28040 Madrid (Spain); Savoini, B.; Monge, M.A. [Departamento de Fisica, Universidad Carlos III de Madrid, 28911 Leganes (Spain); Tucci, A.; Esposito, L. [Centro Ceramico Bologna, 40128 Bologna (Italy); Sanchez-Herencia, A.J. [Instituto de Ceramica y Vidrio, Consejo Superior de Investigaciones Cientificas, 28049 Madrid (Spain)

    2010-05-15

    Positron annihilation spectroscopy (PAS), indentation, nanoindentation experiments and scanning electron microscopy (SEM) observations were performed on Al{sub 2}O{sub 3}-ZrO{sub 2} laminates samples to assess the effect of residual stresses on their mechanical and microstructural properties. Layered samples were implemented by slip-casting, constituted by two thin Al{sub 2}O{sub 3} external layers and an intermediate thick one, consisting of a mixture of Al{sub 2}O{sub 3} and monoclinic ZrO{sub 2} in the range 0-30 vol.%. In these systems residual tensile stresses fields were generated inside the external layers during cooling from the sintering temperature, by the expansion of the adjacent ZrO{sub 2}-containing layer. SEM observations showed the microstructural effects due to the level of tension related to the zirconia content. A correlation between the PAS parameters and the microstructural changes caused by the presence of residual stresses was found. Nanoindentation measurements were used to trace the sign and magnitude of the residual stress gradient across the interface between the layers.

  2. Investigation of amorphous and crystalline phosphates in magnesium phosphate ceramics with solid-state H-1 and P-31 NMR spectroscopy

    Czech Academy of Sciences Publication Activity Database

    Viani, Alberto; Mali, G.; Mácová, Petra

    2017-01-01

    Roč. 43, č. 8 (2017), s. 6571-6579 ISSN 0272-8842 R&D Projects: GA MŠk(CZ) LO1219 Keywords : sol-gel processes * spectroscopy * MgO * chemically-bonded ceramics Subject RIV: JJ - Other Materials Impact factor: 2.986, year: 2016 http://www.sciencedirect.com/science/article/pii/S027288421730278X

  3. Development of a Novel Ceramic Support Layer for Planar Solid Oxide Cells

    DEFF Research Database (Denmark)

    Klemensø, Trine; Boccaccini, Dino; Brodersen, Karen

    2014-01-01

    of the support can be done simultaneously with forming the oxygen electrode, since some of the best performing oxygen electrodes are based on infiltrated LSC. The potential of the proposed structure was investigated by testing the mechanical and electrical properties of the support layer. Comparable strength...

  4. The gradient crystalline structure and microhardness in the treated layer of TC17 via high energy shot peening

    Energy Technology Data Exchange (ETDEWEB)

    Li, Huimin [School of Materials Science and Engineering, Northwestern Polytechnical University, Xi’an 710072 (China); Liu, Yingang, E-mail: lygsuper1987@163.com [School of Materials Science and Engineering, Northwestern Polytechnical University, Xi’an 710072 (China); State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072 (China); Li, Miaoquan, E-mail: honeymli@nwpu.edu.cn [School of Materials Science and Engineering, Northwestern Polytechnical University, Xi’an 710072 (China); State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072 (China); Liu, Hongjie [School of Materials Science and Engineering, Northwestern Polytechnical University, Xi’an 710072 (China)

    2015-12-01

    Graphical abstract: - Highlights: • The gradient nanocrystalline structure was induced in treated layer of TC17. • The thickness of nanograin layer with an average grain size of 10.5 nm was 20 μm. • The composition of the treated layer of TC17 was discussed. • The gradient variation of the microhardness was obtained in treated layer of TC17. - Abstract: The gradient nanocrystalline structure from the topmost surface to the matrix of a bulk coarse-grained TC17 was attained by using high energy shot peening treatment at an air pressure of 0.35 MPa and a processing duration of 30 min. The thickness from the topmost surface with a grain size of about 10.5 nm to the matrix with a micrometer structure was about 120 μm, and the thickness in the nanocrystalline layer was about 20 μm. The microscopic and nanocrystalline structure characteristic in the treated layer were investigated via X-ray diffraction, scanning electron microscopy and high-resolution transmission electron microscopy. The nanograins layer, the nanometer-thick laminated structure layer, the refined grains layer and the low-strain matrix layer occurred in sequence from the topmost surface to the matrix, and therefore the gradient nanocrystalline structure in the treated layer was produced by using high energy shot peening. TEM investigation confirmed that the dislocation activity with very high stacking fault energy induced by surface severe plastic deformation mainly controlled the grain refinement. The microhardness (HV{sub 0.02}) from the topmost surface to the matrix gradually increased by 43% from 440 to 629 and the gradient variation of the microhardness with the depths from the topmost surface to the matrix of treated TC17 was obtained.

  5. Crystalline TiO2: A Generic and Effective Electron-Conducting Protection Layer for Photoanodes and -cathodes

    DEFF Research Database (Denmark)

    Mei, Bastian Timo; Pedersen, Thomas; Malacrida, Paolo

    2015-01-01

    Stabilizing efficient photoabsorbers for solar water splitting has recently shown significant progress with the development of various protection layers. Suitable protection layers for tandem devices should be conductive, transparent, and stable in strongly acidic or alkaline solutions. This paper...... shows that under certain conditions n-type semiconductors, such as TiO2, can be used as protection layers for Si-based photoanodes. It also provides evidence that even in a photoanode assembly TiO2 is conducting only electrons (not holes as in p-type protection layers), and therefore TiO2 can...... be described as a simple ohmic contact. This renders n-type semiconductors, such as TiO2, to be versatile and simple protection layers, which can be used for photoanodes and as previously shown for photocathodes. The ohmic behavior of n-type TiO2 in a Si/TiO2-photoanode assembly is demonstrated under dark...

  6. Particle layering in the ceramic-metal thin film Pt-Al2O3

    Science.gov (United States)

    Gibaud, A.; Hazra, S.; Sella, C.; Laffez, P.; Désert, A.; Naudon, A.; van Tendeloo, G.

    2001-05-01

    Experiments performed by x-ray reflectivity, grazing incidence small angle x-ray scattering (GISAXS), and transmission electron microscopy (TEM) on a cosputtered nanocermet thin film of Pt-Al2O3 are presented. It is shown that the morphology of such a heterogeneous material can be well interpreted by combining the information obtained from the three techniques. In particular, the layering of metal nanoparticles in the immediate vicinity of the substrate is clearly evidenced. GISAXS results are interpreted via a model which yields spherical nanoparticles of diameter 2R=3.1 nm, separated on the average by a distance of 5.8 nm. The evidence for the layering of particles close to the substrate is deduced from the analysis of the specular reflectivity and probed directly by TEM.

  7. Strain and crystalline defects in epitaxial GaN layers studied by high-resolution X-ray diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Chierchia, Rosa

    2007-07-01

    This thesis treats strain and dislocations in MOVPE GaN layers. The mosaic structure of metalorganic vapour phase epitaxy (MOVPE)-grown GaN layers was studied in dependence on the grain diameter utilizing high-resolution XRD. Different models for the defect structure were analyzed, the edge type TD densities were calculated under the assumption that the dislocations are not randomly distributed but localized at the grain boundaries. Moreover, in situ measurements have shown that the layers are under tension in the c-plane when a nucleation layer is used. The second part of this thesis treats a particular approach to reduce dislocations in MOVPE GaN layers, i.e. maskless pendeo epitaxial growth of MOVPE GAN layers. FE simulations assuming the strain to be completely induced during cooling of the structures after growth agree only partly with experimental data. The strain state of single layers and stripes of GaN grown on SiC was studied to exploit the evolution of the strain in the different phases of the PE growth. The biaxial compressive stress, due to the lattice mismatch between the GaN layer and the AlN nucleation layer is plastically relieved before overgrowth. Temperature dependent measurements show a linear reduction of the wing tilt with increasing temperature varying from sample to sample. Bent TDs have been observed in TEM images of maskless PE samples. Stress induced from the mismatch between the AlN buffer layer and the GaN also contributes to the remaining part of the wing tilt not relieved thermally. It has to be noted that the rest tilt value varies from sample to sample at the growth temperature. In fact some of the data indicate that the wing tilt decreases with increasing V/III ratio. In the last Chapter the application of X-ray techniques for the analysis of strain and composition in layers of inhomogeneous composition is explored. In the first part of the Chapter the strain state and the Al content of AlGaN buffer layers grown directly on (0001

  8. Impedance analysis of Bi3.25La0.75Ti3O12 ferroelectric ceramic

    Indian Academy of Sciences (India)

    Abstract. AC impedance spectroscopy technique has been used to study electrical prop- erties of Bi3.25La0.75Ti3O12 (BLT) ceramic. Complex impedance plots were fitted with three depressed semicircles, which are attributed to crystalline layer, plate boundary and grain boundary and all three were found to comprise of ...

  9. Light emitting ceramic device

    Science.gov (United States)

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

    2010-05-18

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

  10. In situ characterization of delamination and crack growth of a CGO–LSM multi-layer ceramic sample investigated by X-ray tomographic microscopy

    DEFF Research Database (Denmark)

    Bjørk, Rasmus; Esposito, Vincenzo; Lauridsen, Erik Mejdal

    2014-01-01

    The densification, delamination and crack growth behavior in a Ce0.9Gd0.1O1.95 (CGO) and (La0.85Sr0.15)0.9MnO3 (LSM) multi-layer ceramic sample was studied using in situ X-ray tomographic microscopy (microtomography) to investigate the critical dynamics of crack propagation and delamination...... and delamination only accelerates when sintering occurs....

  11. Influence of Surface Properties of Filtration-Layer Metal Oxide on Ceramic Membrane Fouling during Ultrafiltration of Oil/Water Emulsion.

    Science.gov (United States)

    Lu, Dongwei; Zhang, Tao; Gutierrez, Leo; Ma, Jun; Croué, Jean-Philippe

    2016-05-03

    In this work, ceramic ultrafiltration membranes deposited with different metal oxides (i.e., TiO2, Fe2O3, MnO2, CuO, and CeO2) of around 10 nm in thickness and similar roughness were tested for O/W emulsion treatment. A distinct membrane fouling tendency was observed, which closely correlated to the properties of the filtration-layer metal oxides (i.e., surface hydroxyl groups, hydrophilicity, surface charge, and adhesion energy for oil droplets). Consistent with the distinct bond strength of the surface hydroxyl groups, hydrophilicity of these common metal oxides is quite different. The differences in hydrophilicity consequently lead to different adhesion of these metal oxides toward oil droplets, consistent with the irreversible membrane fouling tendency. In addition, the surface charge of the metal oxide opposite to that of emulsion can help to alleviate irreversible membrane fouling in ultrafiltration. Highly hydrophilic Fe2O3 with the lowest fouling tendency could be a potential filtration-layer material for the fabrication/modification of ceramic membranes for O/W emulsion treatment. To the best of our knowledge, this is the first study clearly showing the correlations between surface properties of filtration-layer metal oxides and ceramic membrane fouling tendency by O/W emulsion.

  12. Influence of surface properties of filtration-layer metal oxide on ceramic membrane fouling during ultrafiltration of oil/water emulsion

    KAUST Repository

    Lu, Dongwei

    2016-04-01

    In this work, ceramic ultrafiltration membranes deposited with different metal oxides (i.e., TiO2, Fe2O3, MnO2, CuO, and CeO2) of around 10 nm in thickness and similar roughness were tested for O/W emulsion treatment. Distinct membrane fouling tendency was observed, which closely correlated to the properties of the filtration-layer metal oxides (i.e. surface hydroxyl groups, hydrophilicity, surface charge, and adhesion energy for oil droplets). In consistent with the distinct bond strength of the surface hydroxyl groups, hydrophilicity of these common metal oxides are quite different. The differences in hydrophilicity consequently lead to different adhesion of these metal oxides towards oil droplets which consists very well with irreversible membrane fouling tendency. In addition, the surface charge of the metal oxide opposite to that of emulsion can help to alleviate irreversible membrane fouling in ultrafiltration. Highly hydrophilic Fe2O3 with lowest fouling tendency could be a potential filtration-layer material for the fabrication/modification of ceramic membranes for O/W emulsion treatment. To the best of our knowledge, this is the first study clearly showing the correlations between surface properties of filtration-layer metal oxides and ceramic membrane fouling tendency by O/W emulsion.

  13. Relation of lifetime to surface passivation for atomic-layer-deposited Al{sub 2}O{sub 3} on crystalline silicon solar cell

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Young Joon [Graduate School of Energy Science and Technology, Chungnam National University, Yuseong-gu, Daejeon 305-764 (Korea, Republic of); Song, Hee Eun, E-mail: hsong@kier.re.kr [Photovoltaic Center, Korea Institute of Energy Research, Yuseong-gu, Daejeon 305-343 (Korea, Republic of); Chang, Hyo Sik, E-mail: hschang@cnu.ac.kr [Graduate School of Energy Science and Technology, Chungnam National University, Yuseong-gu, Daejeon 305-764 (Korea, Republic of)

    2015-03-15

    Highlights: • We investigated the relation of potassium contamination on Si solar wafer to lifetime. • We deposited Al{sub 2}O{sub 3} layer by atomic layer deposition (ALD) on Si solar wafer after several cleaning process. • Potassium can be left on Si surface by incomplete cleaning process and degrade the Al{sub 2}O{sub 3} passivation quality. - Abstract: We investigated the relation of potassium contamination on a crystalline silicon (c-Si) surface after potassium hydroxide (KOH) etching to the lifetime of the c-Si solar cell. Alkaline solution was employed for saw damage removal (SDR), texturing, and planarization of a textured c-Si solar wafer prior to atomic layer deposition (ALD) Al{sub 2}O{sub 3} growth. In the solar-cell manufacturing process, ALD Al{sub 2}O{sub 3} passivation is utilized to obtain higher conversion efficiency. ALD Al{sub 2}O{sub 3} shows excellent surface passivation, though minority carrier lifetime varies with cleaning conditions. In the present study, we investigated the relation of potassium contamination to lifetime in solar-cell processing. The results showed that the potassium-contaminated samples, due to incomplete cleaning of KOH, had a short lifetime, thus establishing that residual potassium can degrade Al{sub 2}O{sub 3} surface passivation.

  14. Variation in the Optical Properties of the SiC-SiO2 Composite Antireflection Layer in Crystalline Silicon Solar Cells by Annealing

    Science.gov (United States)

    Jannat, Azmira; Li, Zhen Yu; Akhter, M. Shaheer; Yang, O.-Bong

    2017-11-01

    This study showed the effects of annealing on a sol-gel-derived SiC-SiO2 composite antireflection (AR) layer and investigated the optical and photovoltaic properties of crystalline silicon (Si) solar cells. The SiC-SiO2 composite AR coating showed a considerable decrease in reflectance from 7.18% to 3.23% at varying annealing temperatures of 450-800°C. The refractive indices of the SiC-SiO2 composite AR layer were tuned from 2.06 to 2.45 with the increase in annealing temperature. The analysis of the current density-voltage characteristics indicated that the energy conversion efficiencies of the fabricated Si solar cells gradually increased from 16.99% to 17.73% with increasing annealing temperatures of 450-800°C. The annealing of the SiC-SiO2 composite AR layer in Si solar cells was crucial to improving the optical, morphological, and photovoltaic properties.

  15. Using (18)O/(16)O exchange to probe an equilibrium space-charge layer at the surface of a crystalline oxide: method and application.

    Science.gov (United States)

    De Souza, Roger A; Martin, Manfred

    2008-05-07

    The use of an (18)O/(16)O exchange experiment as a means for probing surface space-charge layers in oxides is examined theoretically and experimentally. On the basis of a theoretical treatment, isotope penetration profiles are calculated for (18)O/(16)O exchange across a gas-solid interface and subsequent diffusion of the labelled isotope through an equilibrium space-charge layer depleted of mobile oxygen vacancies and into a homogeneous bulk phase. Profiles calculated for a range of conditions all have a characteristic shape: a sharp drop in isotope fraction close to the surface followed by a normal bulk diffusion profile. Experimental (18)O profiles in an exchanged (001) oriented single crystal of Fe-doped SrTiO(3) were measured by time-of-flight secondary ion mass spectrometry (ToF-SIMS). By extracting the space-charge potential from such profiles, we demonstrate that this method allows the spatially resolved characterization of space-charge layers at the surfaces of crystalline oxides under thermodynamically well-defined conditions.

  16. Wearable high-performance supercapacitors based on Ni-coated cotton textile with low-crystalline Ni-Al layered double hydroxide nanoparticles.

    Science.gov (United States)

    Lu, Haicui; Chen, Jizhang; Tian, Qinghua

    2017-11-16

    Wearable electronics are developing rapidly in recent years. In this work, we develop a cost-effective, facile, and scalable approach to transform insulating cotton textile to highly conductive Ni-coated cotton textile (NCT). In order to verify the feasibility of NCT as a flexible current collector for wearable supercapacitors, we electrodeposit low-crystalline Ni-Al layered double hydroxide (LDH) nanoparticles onto the NCT. The obtained NCT@NiAl-LDH shows high specific capacitance (935.2 mF cm -2 ), superior rate capability, and good cyclability. Besides, the asymmetric supercapacitor (ASC) assembled from NCT@NiAl-LDH exhibits high specific energy of 58.8 Wh kg -1 (134 μWh cm -2 ) when the specific power is 539 W kg -1 (1228 μW cm -2 ). The results demonstrate great potential of our methodology. Copyright © 2017 Elsevier Inc. All rights reserved.

  17. In vitro chipping behaviour of all-ceramic crowns with a zirconia framework and feldspathic veneering: comparison of CAD/CAM-produced veneer with manually layered veneer.

    Science.gov (United States)

    Schmitter, M; Mueller, D; Rues, S

    2013-07-01

    The purpose of this in vitro study was to assess the breaking load of zirconia-based crowns veneered with either CAD/CAM-produced or manually layered feldspathic ceramic. Thirty-two identical zirconia frameworks (Sirona inCoris ZI, mono L F1), 0·6 mm thick with an anatomically shaped occlusal area, were constructed (Sirona inLab 3.80). Sixteen of the crowns were then veneered by the use of CAD/CAM-fabricated feldspathic ceramic (CEREC Bloc, Sirona) and 16 by the use of hand-layered ceramic. The CAD/CAM-manufactured veneer was attached to the frameworks by the use of Panavia 2.0 (Kuraray). Half of the specimens were loaded until failure without artificial ageing; the other half of the specimens underwent thermal cycling and cyclic loading (1·2 million chewing cycles, force magnitude F(max) = 108 N) before the assessment of the ultimate load. To investigate the new technique further, finite element (FE) computations were conducted on the basis of the original geometry. Statistical assessment was made by the use of non-parametric tests. Initial breaking load was significantly higher in the hand-layered group than in the CAD/CAM group (mean: 1165·86 N versus 395·45 N). During chewing simulation, however, 87·5% (7/8) of the crowns in the hand-layered group failed, whereas no crown in the CAD/CAM group failed. The CAD/CAM-produced veneer was significantly less sensitive to ageing than the hand-layered veneer. © 2013 John Wiley & Sons Ltd.

  18. Effects of anodizing conditions and annealing temperature on the morphology and crystalline structure of anodic oxide layers grown on iron

    Science.gov (United States)

    Pawlik, Anna; Hnida, Katarzyna; Socha, Robert P.; Wiercigroch, Ewelina; Małek, Kamilla; Sulka, Grzegorz D.

    2017-12-01

    Anodic iron oxide layers were formed by anodization of the iron foil in an ethylene glycol-based electrolyte containing 0.2 M NH4F and 0.5 M H2O at 40 V for 1 h. The anodizing conditions such as electrolyte composition and applied potential were optimized. In order to examine the influence of electrolyte stirring and applied magnetic field, the anodic samples were prepared under the dynamic and static conditions in the presence or absence of magnetic field. It was shown that ordered iron oxide nanopore arrays could be obtained at lower anodizing temperatures (10 and 20 °C) at the static conditions without the magnetic field or at the dynamic conditions with the applied magnetic field. Since the as-prepared anodic layers are amorphous in nature, the samples were annealed in air at different temperatures (200-500 °C) for a fixed duration of time (1 h). The morphology and crystal phases developed after anodization and subsequent annealing were characterized using field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. The results proved that the annealing process transforms the amorphous layer into magnetite and hematite phases. In addition, the heat treatment results in a substantial decrease in the fluorine content and increase in the oxygen content.

  19. Silica-sol-based spin-coating barrier layer against phosphorous diffusion for crystalline silicon solar cells

    Science.gov (United States)

    Uzum, Abdullah; Fukatsu, Ken; Kanda, Hiroyuki; Kimura, Yutaka; Tanimoto, Kenji; Yoshinaga, Seiya; Jiang, Yunjian; Ishikawa, Yasuaki; Uraoka, Yukiharu; Ito, Seigo

    2014-12-01

    The phosphorus barrier layers at the doping procedure of silicon wafers were fabricated using a spin-coating method with a mixture of silica-sol and tetramethylammonium hydroxide, which can be formed at the rear surface prior to the front phosphorus spin-on-demand (SOD) diffusion and directly annealed simultaneously with the front phosphorus layer. The optimization of coating thickness was obtained by changing the applied spin-coating speed; from 2,000 to 8,000 rpm. The CZ-Si p-type silicon solar cells were fabricated with/without using the rear silica-sol layer after taking the sheet resistance measurements, SIMS analysis, and SEM measurements of the silica-sol material evaluations into consideration. For the fabrication of solar cells, a spin-coating phosphorus source was used to form the n+ emitter and was then diffused at 930°C for 35 min. The out-gas diffusion of phosphorus could be completely prevented by spin-coated silica-sol film placed on the rear side of the wafers coated prior to the diffusion process. A roughly 2% improvement in the conversion efficiency was observed when silica-sol was utilized during the phosphorus diffusion step. These results can suggest that the silica-sol material can be an attractive candidate for low-cost and easily applicable spin-coating barrier for any masking purpose involving phosphorus diffusion.

  20. Silica-sol-based spin-coating barrier layer against phosphorous diffusion for crystalline silicon solar cells.

    Science.gov (United States)

    Uzum, Abdullah; Fukatsu, Ken; Kanda, Hiroyuki; Kimura, Yutaka; Tanimoto, Kenji; Yoshinaga, Seiya; Jiang, Yunjian; Ishikawa, Yasuaki; Uraoka, Yukiharu; Ito, Seigo

    2014-01-01

    The phosphorus barrier layers at the doping procedure of silicon wafers were fabricated using a spin-coating method with a mixture of silica-sol and tetramethylammonium hydroxide, which can be formed at the rear surface prior to the front phosphorus spin-on-demand (SOD) diffusion and directly annealed simultaneously with the front phosphorus layer. The optimization of coating thickness was obtained by changing the applied spin-coating speed; from 2,000 to 8,000 rpm. The CZ-Si p-type silicon solar cells were fabricated with/without using the rear silica-sol layer after taking the sheet resistance measurements, SIMS analysis, and SEM measurements of the silica-sol material evaluations into consideration. For the fabrication of solar cells, a spin-coating phosphorus source was used to form the n(+) emitter and was then diffused at 930°C for 35 min. The out-gas diffusion of phosphorus could be completely prevented by spin-coated silica-sol film placed on the rear side of the wafers coated prior to the diffusion process. A roughly 2% improvement in the conversion efficiency was observed when silica-sol was utilized during the phosphorus diffusion step. These results can suggest that the silica-sol material can be an attractive candidate for low-cost and easily applicable spin-coating barrier for any masking purpose involving phosphorus diffusion.

  1. Combining Esthetic Layering and Lithium Disilicate Sintering Technique on Zirconia Frameworks: A Veneering Option to Prevent Ceramic Chipping.

    Science.gov (United States)

    Saeidi Pour, Reza; Edelhoff, Daniel; Rafael, Caroline Freitas; Prandtner, Otto; Frei, Stefan; Maziero Volpato, Claudia Angela; Liebermann, Anja

    Major and minor chipping of veneering porcelain are two of the most frequent complications in all-ceramic restorations with zirconia frameworks. In cases of major chipping, replacement of the affected restoration may be necessary. High-strength lithium disilicate ceramic offers new options to serve as veneering material in a sintering technique or as repair material for chipping in combination with the adhesive technique. The purpose of three case presentations here was to describe the use of lithium disilicate ceramic on zirconia frameworks for reliable and esthetic veneering in the posterior region and to repair extended chipping in conventional veneering materials.

  2. SEM-EPMA observation of three types of apatite-containing glass-ceramics implanted in bone: the variance of a Ca-P-rich layer.

    Science.gov (United States)

    Kitsugi, T; Nakamura, T; Yamamura, T; Kokubu, T; Shibuya, T; Takagi, M

    1987-10-01

    The progressive changes of a Ca-P-rich layer between bone and three types of apatite-containing glass-ceramics of the same chemical composition: MgO 4.6, CaO 44.9, SiO2 34.2, P2O5 16.3, CaF2 0.5 (in weight ratio) were examined. Plates (15 mm X 10 mm X 2 mm, mirror surface) containing apatite (35 wt%) (designated A-GC), apatite (35 wt%) and wollastonite (40 wt%) (designated A.W-GC), and apatite (20 wt%), wollastonite (55 wt%), and whitlockite (15 wt%) (designated A.W.CP-GC) were prepared. They were implanted into the tibia of mature male rabbits for 5 days, 10 days, 20 days, 30 days, 60 days, 6 months, and 12 months. All three types of glass-ceramics showed direct bonding to the bone 30 days after implantation. It was observed by SEM-EPMA 30 days after implantation that Si and Mg content decreased, P content increased, and Ca content did not change across the reactive zone from the glass-ceramics to bone. The level of P and Si in the A.W.CP-GC changed five days after implantation. In A.W-GC and A-GC, a little change in P and Si levels was observed between 10 and 20 days after implantation. The width of reactive zone was narrowest with A-GC, wider with A.W-GC, and widest with A.W.CP-GC. The dissolution of glass-ceramics stopped 6 months after implantation. This phenomenon shows that the glass-ceramics may be suitable for clinical use.

  3. Crystalline MoOx Thin-Films as Hole Transport Layers in DBP/C70 Based Organic Solar Cell

    DEFF Research Database (Denmark)

    Ahmadpour, Mehrad; Fernandes Cauduro, André Luis; dos Reis, Roberto

    Transition Metal Oxides such as Molybdenum oxide (MoOx) have been intensively used as hole transport layers in different organic, inorganic and hybrid technologies, demonstrating also important improvements on the power conversion efficiency as well as on the stability of different types of solar...... cells. Among several different deposition methods available for fabrication of MoOx thin-films, reactive sputtering arises as an interesting alternative due to its full control over the deposition parameters such as the deposition power, reactive gas partial pressure and the deposition rate....

  4. PECVD-ONO: A New Deposited Firing Stable Rear Surface Passivation Layer System for Crystalline Silicon Solar Cells

    Directory of Open Access Journals (Sweden)

    M. Hofmann

    2008-01-01

    Full Text Available A novel plasma-enhanced chemical vapour deposited (PECVD stack layer system consisting of a-SiOx:H, a-SiNx:H, and a-SiOx:H is presented for silicon solar cell rear side passivation. Surface recombination velocities below 60 cm/s (after firing and below 30 cm/s (after forming gas anneal were achieved. Solar cell precursors without front and rear metallisation showed implied open-circuit voltages Voc values extracted from quasi-steady-state photoconductance (QSSPC measurements above 680 mV. Fully finished solar cells with up to 20.0% energy conversion efficiency are presented. A fit of the cell's internal quantum efficiency using software tool PC1D and a comparison to a full-area aluminium-back surface field (Al-BSF and thermal SiO2 is shown. PECVD-ONO was found to be clearly superior to Al-BSF. A separation of recombination at the metallised and the passivated area at the solar cell's rear is presented using the equations of Fischer and Kray. Nuclear reaction analysis (NRA has been used to evaluate the hydrogen depth profile of the passivation layer system at different stages.

  5. Comparison of three and four point bending evaluation of two adhesive bonding systems for glass-ceramic zirconia bi-layered ceramics.

    Science.gov (United States)

    Gee, C; Weddell, J N; Swain, M V

    2017-09-01

    To quantify the adhesion of two bonding approaches of zirconia to more aesthetic glass-ceramic materials using the Schwickerath (ISO 9693-2:2016) three point bend (3PB) [1] test to determine the fracture initiation strength and strain energy release rate associated with stable crack extension with this test and the Charalamabides et al. (1989) [2] four point bend (4PB) test. Two glass-ceramic materials (VITABLOCS Triluxe forte, Vita Zahnfabrik, Germany and IPS.emax CAD, Ivoclar Vivadent, Liechtenstein) were bonded to sintered zirconia (VITA InCeram YZ). The former was resin bonded using a dual-cure composite resin (Panavia F 2.0, Kuraray Medical Inc., Osaka, Japan) following etching and silane conditioning, while the IPS.emax CAD was glass bonded (IPS e.max CAD Crystall/Connect) during crystallization of the IPS.emax CAD. Specimens (30) of the appropriate dimensions were fabricated for the Schwickerath 3PB and 4PB tests. Strength values were determined from crack initiation while strain energy release rate values were determined from the minima in the force-displacement curves with the 3PB test (Schneider and Swain, 2015) [3] and for 4PB test from the plateau region of stable crack extension. Strength values for the resin and glass bonded glass ceramics to zirconia were 22.20±6.72MPa and 27.02±3.49MPa respectively. The strain energy release rates for the two methods used were very similar and for the glass bonding, (4PB) 15.14±5.06N/m (or J/m2) and (3PB) 16.83±3.91N/m and resin bonding (4PB) 8.34±1.93N/m and (3PB) 8.44±2.81N/m respectively. The differences in strength and strain energy release rate for the two bonding approaches were statistically significant (pzirconia. Copyright © 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  6. Flux Growth of Highly Crystalline Photocatalytic BaTiO3 Particle Layers on Porous Titanium Sponge Substrate and Insights into the Formation Mechanism

    Science.gov (United States)

    Wang, Q.; Li, B.

    2017-09-01

    A unique architecture of idiomorphic and highly crystalline BaTiO3 particle layers directly grown on a porous titanium sponge substrate was successfully achieved for the first time using a facile molten salt method at a relatively low temperature of 700 °C. Specifically, the low-melting KCl-NaCl eutectic salts and barium hydroxide octahydrate were employed as the reaction medium and barium source, respectively. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and UV-vis diffuse reflectance spectrophotometry were used to characterize the structure, morphology and optical property of the obtained samples. The results revealed that the flux-grown tetragonal BaTiO3 products had well-defined and uniform morphology with an average size of 300 nm and a band gap of ∼3.16 eV. Based on XRD, EDS, SEM, and TEM, the possible formation mechanism responsible for the well-developed architecture of BaTiO3 particle layers was proposed and discussed. Furthermore, the photocatalytic activity of the flux-grown BaTiO3 products for organic pollutant degradation under simulated sunlight irradiation was also investigated.

  7. Comparison of the metal-to-ceramic bond strengths of four noble alloys with press-on-metal and conventional porcelain layering techniques.

    Science.gov (United States)

    Khmaj, Mofida R; Khmaj, Abdulfatah B; Brantley, William A; Johnston, William M; Dasgupta, Tridib

    2014-11-01

    New noble alloys for metal ceramic restorations introduced by manufacturers are generally lower-cost alternatives to traditional higher-gold alloys. Information about the metal-to-ceramic bond strength for these alloys, which is needed for rational clinical selection, is often lacking. The purpose of this study was to evaluate the bond strength of 4 recently introduced noble alloys by using 2 techniques for porcelain application. Aquarius Hard (high-gold: 86.1 gold, 8.5 platinum, 2.6 palladium, 1.4 indium; values in wt. %), Evolution Lite (reduced-gold: 40.3 gold, 39.3 palladium, 9.3 indium, 9.2 silver, 1.8 gallium), Callisto 75 Pd (palladium-silver containing gold: 75.2 palladium, 7.1 silver, 2.5 gold, 9.3 tin, 1.0 indium), and Aries, (conventional palladium-silver: 63.7 palladium, 26.0 silver, 7.0 tin, 1.8 gallium, 1.5 indium) were selected for bonding to leucite-containing veneering porcelains. Ten metal ceramic specimens that met dimensional requirements for International Organization for Standardization (ISO) Standard 9693 were prepared for each alloy by using conventional porcelain layering and press-on-metal methods. The 3-point bending test in ISO Standard 9693 was used to determine bond strength. Values were compared with 2-way ANOVA (maximum likelihood analysis, SAS Mixed Procedure) and the Tukey test (α=.05). Means (standard deviations) for bond strength with conventional porcelain layering were as follows: Aquarius Hard (50.7 ±5.5 MPa), Evolution Lite (40.2 ±3.3 MPa), Callisto 75 Pd (37.2 ±3.9 MPa), and Aries (34.0 ±4.9 MPa). For the press-on-metal technique, bond strength results were as follows: Aquarius Hard (33.7 ±11.5 MPa), Evolution Lite (34.9 ±4.5 MPa), Callisto 75 Pd (37.2 ±11.9 MPa), and Aries (30.7 ±10.8 MPa). From statistical analyses, the following 3 significant differences were found for metal-to-ceramic bond strength: the bond strength for Aquarius Hard was significantly higher for conventional porcelain layers compared with

  8. Testing method for ceramic armour and bare ceramic tiles

    NARCIS (Netherlands)

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

    2016-01-01

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

  9. Testing method for ceramic armor and bare ceramic tiles

    NARCIS (Netherlands)

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

    2014-01-01

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

  10. Low-Temperature Sintering and Microwave Dielectric Properties of Zn2SiO4 Ceramic Added with Crystalline Zinc Borate

    Science.gov (United States)

    Chaware, Varsha; Deshmukh, Ravindra; Sarode, Chetan; Gokhale, Suresh; Phatak, Girish

    2015-07-01

    The physical and dielectric properties of composites of known microwave materials, Zn2SiO4 and Zn3B2O6, prepared by solid-state reaction, were investigated with the purpose of developing a low-loss dielectric material for low-temperature co-fired ceramic applications. An off-stoichiometric phase of Zn2SiO4 with extra SiO2 was used to avoid the occurrence of unreacted ZnO. During sintering, zinc borate was found to partially react with residual SiO2 to form Zn2SiO4. The residual zinc borate was converted to a boron-rich glassy phase which helped to reduce the sintering temperature of the composite. Good relative sintering density (>90%) at temperatures below the melting temperature of zinc borate is indicative of a sintering mechanism of diffusion-based mass transfer. Composites containing 15 wt.% zinc borate, 2.5 wt.% lithium carbonate and 20 wt.% zinc borate in zinc silicate had dielectric constants of 6.8 and 6.1, quality factors (Q×f) of 48,800 and 94,300 GHz when sintered at 900°C and 950°C, respectively. These quality factor results are close to the best values reported for zinc silicate at these sintering temperatures.

  11. Anions derived from squaric acid form interionic pi-stack and layered, hydrogen-bonded superstructures with organometallic sandwich cations: the magnetic behaviour of crystalline

    Science.gov (United States)

    Braga; Maini; Prodi; Caneschi; Sessoli; Grepioni

    2000-04-14

    Depending on the stoichiometric ratio, squaric acid (3,4-dihydroxy-3-cyclobutene-1,2-dione, H2SQA) reacts with [(eta6-C6H6)2Cr] in THF to form the crystalline material [(eta6-C6H6)2Cr][HSQA] (1) and in water to yield [[(eta6-C6H6)2Cr]2][SQA] x 6H2O (3); it also reacts with [(eta5-C5H5)2Co][OH] in water to form [[(eta5-C5H5)2Co]2][SQA] x 6H2O (4). Compound 1 is almost isostructural with the previously reported salt [(eta5-C5H5)2Co][HSQA] (2); its structure is based on pi-pi stacks between the benzene ligands and the hydrogen squarate anionic chains (pi-pi distance 3.375 A). Compounds 3 and 4 are isomorphous and have a structure in which layers of organometallic cations intercalate with layers of water molecules hydrogen bonded to squarate dianions. All crystals contain charge-assisted C-Hdelta+...Odelta- hydrogen bonds between the organometallic and the organic components, while negative O-H(-)...O(-) and O-H...O(2-) interactions are present in the pairs 1/3 and 2/4, respectively. In constrast to most organic salts of [(eta6-C6H6)2Cr]+ and [(eta5-C5H5)2Co]+ which are yellow, crystals of compounds 1-4 are orange. Reflectance spectra measured on the crystalline material 1 show the presence of an intense tail that can be assigned to a charge-transfer transition through the [(eta6-C6H6)2Cr]+/[HSQA]- pi-stacking interactions, while the pi stacking in 2 causes only a broadening of the band. The magnetic behaviour of 1 and 3 has been investigated by SQUID magnetometry. Both compounds are characterised by a weak antiferromagnetic interaction between the S=1/2 Cr centres of the [(eta6-C6H6)2Cr]+ cations, which is significantly stronger in 1 due to the pi-stacking with the HSQA- anions.

  12. EFFECTS OF INCORPORATING NATURAL MINERALS ON PRODUCTION AND BIOACTIVITY OF BIOACTIVE GLASS CERAMICS

    Directory of Open Access Journals (Sweden)

    Franco Matias Stabile

    2016-07-01

    Full Text Available Two glass-ceramics composition were produced from natural minerals. Quartzes and feldspars were pre-selected on the basis of their purities studied by X-ray diffraction (XRD and chemical analysis. Prepared compositions of glasses precursors were two different theoretical leucite (KAlSi₂O₆ /Bioglass 45S5 (L/Bg ratios. Transformations of raw materials mixtures and glass precursors were studied by differential thermal analyses. On the basis of thermal analysis results, glass ceramics were produced and characterized by XRD. Glass-ceramics were composed of two major crystalline phases, leucite and sodium calcium silicate. Bioactivity tests were performed submerging the glass-ceramics into simulated body fluid (SBF for different periods (1, 5 and 10 days. Bioactive behavior was monitored by XRD and scanning electron microscopy (SEM. Studied samples were found to be bioactive, in which hydroxyapatite layer was developed within 5 days of contact with SBF.

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

    Science.gov (United States)

    de Diego, Peter; Zhang, James

    2017-05-30

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

  14. FEM numerical analysis of excimer laser induced modification in alternating multi-layers of amorphous and nano-crystalline silicon films

    Energy Technology Data Exchange (ETDEWEB)

    Conde, J.C., E-mail: jconde@uvigo.es [Dpto. Fisica Aplicada, Universidade de Vigo, Rua Maxwell s/n, Campus Universitario Lagoas Marcosende, Vigo (Spain); Martin, E. [Dpto. Mecanica, Maquinas, Motores Termicos y Fluidos, Universidade de Vigo, Rua Maxwell s/n, Campus Universitario Lagoas Marcosende, Vigo (Spain); Stefanov, S. [Dpto. Fisica Aplicada, Universidade de Vigo, Rua Maxwell s/n, Campus Universitario Lagoas Marcosende, Vigo (Spain); Alpuim, P. [Departamento de Fisica, Universidade do Minho, 4800-058 Guimaraes (Portugal); Chiussi, S. [Dpto. Fisica Aplicada, Universidade de Vigo, Rua Maxwell s/n, Campus Universitario Lagoas Marcosende, Vigo (Spain)

    2012-09-15

    Highlights: Black-Right-Pointing-Pointer nc-Si:H is a material with growing importance for a large-area of nano-electronic, photovoltaic or biomedical devices. Black-Right-Pointing-Pointer UV-ELA technique causes a rapid heating that provokes the H{sub 2} desorption from the Si surface and bulk material. Black-Right-Pointing-Pointer Next, diffusion of P doped nc-Si films and eventually, for high energy densities would be possible to reach the melting point. Black-Right-Pointing-Pointer These multilayer structures consisting of thin alternating a-Si:H(10 nm) and n-doped nc-Si:H(60 nm) films deposited on SiO{sub 2}. Black-Right-Pointing-Pointer To optimize parameters involved in this processing, FEM numerical analysis of multilayer structures have been performed. Black-Right-Pointing-Pointer The numerical results are compared with exhaustive characterization of the experimental results. - Abstract: UV excimer laser annealing (UV-ELA) is an alternative annealing process that, during the last few years, has gained enormous importance for the CMOS nano-electronic technologies, with the ability to provide films and alloys with electrical and optical properties to fit the desired device performance. The UV-ELA of amorphous (a-) and/or doped nano-crystalline (nc-) silicon films is based on the rapid (nanoseconds) formation of temperature profiles caused by laser radiation that is absorbed in the material and lead to crystallisation, diffusion in solid or even in liquid phase. To achieve the desired temperature profiles and to optimize the parameters involved in the processing of hydrogenated nanocrystalline silicon (nc-Si:H) films with the UV-ELA, a numerical analysis by finite element method (FEM) of a multilayer structure has been performed. The multilayer structures, consisting of thin alternating a-Si:H(10 nm) and n-doped nc-Si:H(60 nm) layers, deposited on a glass substrate, has also been experimentally analyzed. Temperature profiles caused by 193 nm radiation with 25

  15. Ceramic hot-gas filter

    Science.gov (United States)

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

    1999-01-01

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

  16. Bi-layered zirconia/fluor-apatite bridges supported by ceramic dental implants: a prospective case series after thirty months of observation.

    Science.gov (United States)

    Spies, Benedikt Christopher; Witkowski, Siegbert; Butz, Frank; Vach, Kirstin; Kohal, Ralf-Joachim

    2016-10-01

    The aim of this study was to determine the success and survival rate of all-ceramic bi-layered implant-supported three-unit fixed dental prostheses (IS-FDPs) 3 years after implant placement. Thirteen patients (seven males, six females; age: 41-78 years) received two one-piece ceramic implants (alumina-toughened zirconia) each in the region of the premolars or the first molar and were finally restored with adhesively cemented bi-layered zirconia-based IS-FDPs (3 in the maxilla, 10 in the mandible) composed of CAD/CAM-fabricated zirconia frameworks pressed-over with fluor-apatite glass-ceramic ingots. At prosthetic delivery and the follow-ups after 1, 2 and 3 years, the restorations were evaluated using modified United States Public Health Service (USPHS) criteria. Restorations with minor veneer chippings, a small-area occlusal roughness, slightly soundable restoration margins, minimal contour deficiencies and tolerable color deviations were regarded as success. In case of more distinct defects that could, however, be repaired to a clinically acceptable level, IS-FDPs were regarded as surviving. Kaplan-Meier plots were used for the success/survival analyses. To verify an impact on subjective patients' perceptions, satisfaction was evaluated by visual analog scales (VAS). All patients were seen 3 years after implant installation. No IS-FDP had to be replaced, resulting in 100% survival after a mean observation period of 29.5 months (median: 30.7). At the 3-year follow-up, 7/13 IS-FDPs showed a veneer chipping, 13/13 an occlusal roughness and 12/13 minimal deficiencies of contour/color. Since six restorations showed a major chipping and/or a major occlusal roughness, the Kaplan-Meier success rate was 53.8%. However, patients' significantly improved perceptions of function, esthetics, sense, and speech at prosthetic delivery remained stable over time. Bi-layered zirconia/fluor-apatite IS-FDPs entirely survived the observation period but showed a high frequency of

  17. Visible photoinduced hydrophilicity of V{sub 2}O{sub 5}-TiO{sub 2} nanoporous ceramic layers grown via micro-arc oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Bayati, M R; Molaei, Roya, E-mail: bayati@iust.ac.i [School of Metallurgy and Materials Engineering, Iran University of Science and Technology, PO Box 16845-161, Tehran (Iran, Islamic Republic of)

    2010-12-22

    V{sub 2}O{sub 5}-TiO{sub 2} porous layers with a pore size of 50-400 nm were synthesized via a micro-arc oxidation process under different applied voltages. Morphological and topographical studies, performed by SEM and AFM techniques, revealed a nanoporous morphology with a rough surface where the pores' size as well as the surface roughness increased with voltage. In addition, our XRD and XPS results demonstrated that the layers consisted of anatase, rutile and vanadia phases. It was also found that V{sub 2}O{sub 5} not only dispersed in the TiO{sub 2} matrix, but also doped into the crystalline lattice. Hydrophilicity of the synthesized layers was determined using a water contact angle apparatus. It was observed that the layer synthesized under the applied voltage of 450 V exhibited the highest hydrophilicity. Finally, a correlation between measured contact angles and MAO parameters was suggested with emphasis on the electrochemical foundations.

  18. Crystalline Bioceramic Materials

    Directory of Open Access Journals (Sweden)

    de Aza, P. N.

    2005-06-01

    Full Text Available A strong interest in the use of ceramics for biomedical engineering applications developed in the late 1960´s. Used initially as alternatives to metallic materials in order to increase the biocompatibility of implants, bioceramics have become a diverse class of biomaterials, presently including three basic types: relatively bioinert ceramics; bioactive or surface reactive bioceramics and bioresorbable ceramics. This review will only refer to bioceramics “sensus stricto”, it is to say, those ceramic materials constituted for nonmetallic inorganic compounds, crystallines and consolidated by thermal treatments of powders to high temperatures. Leaving bioglasses, glass-ceramics and biocements apart, since, although all of them are obtained by thermal treatments to high temperatures, the first are amorphous, the second are obtained by desvitrification of a glass and in them vitreous phase normally prevails on the crystalline phases and the third are consolidated by means of a hydraulic or chemical reaction to room temperature. A review of the composition, physiochemical properties and biological behaviour of the principal types of crystalline bioceramics is given, based on the literature data and on the own experience of the authors.

    A finales de los años sesenta se despertó un gran interés por el uso de los materiales cerámicos para aplicaciones biomédicas. Inicialmente utilizados como una alternativa a los materiales metálicos, con el propósito de incrementar la biocompatibilidad de los implantes, las biocerámicas se han convertido en una clase diversa de biomateriales, incluyendo actualmente tres tipos: cerámicas cuasi inertes; cerámicas bioactivas o reactivas superficialmente y cerámicas reabsorbibles o biodegradables. En la presente revisión se hace referencia a las biocerámicas en sentido estricto, es decir, a aquellos materiales constitutitos por compuestos inorgánicos no metálicos, cristalinos y consolidados

  19. Ceramic Composite Thin Films

    Science.gov (United States)

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

    2013-01-01

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

  20. Influence of temperature on the dielectric nonlinearity of BaTiO{sub 3}-based multi-layer ceramic capacitors

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Seok-Hyun, E-mail: seokhyun72.yoon@samsung.com; Kim, Mi-Yang [LCR Materials Group, Corporate R& D Institute, Samsung Electro-Mechanics Co., Ltd., Suwon, Gyunggi-Do 443-743 (Korea, Republic of)

    2016-06-13

    Temperature dependence of the dielectric nonlinearity was investigated for the BaTiO{sub 3} multilayer ceramic capacitor. The decrease in temperature caused a significant increase in the degree of dielectric nonlinearity. The Preisach analysis shows that such effect corresponds to a decrease in reversible and a significant increase in irreversible domain wall contribution to polarization. The magnitude of spontaneous polarization (P{sub S}) was increased with decreasing temperature. It can be associated with phase transition from pseudo-cubic to monoclinic and its resultant change in the polar direction, which was observed through transmission electron microscopy. These results demonstrate that the increase in P{sub S} with the decrease in temperature inhibits domain wall motion in low driving field as it is anticipated to increase the degree of intergranular constraints during domain wall motion. But it results in a more steep increase in the dielectric constants beyond the threshold field where domain wall motion can occur.

  1. Dynamic and Steady Characteristics of Polymer-Ceramic Pressure-Sensitive Paint with Variation in Layer Thickness

    Science.gov (United States)

    Hayashi, Tatsunori; Sakaue, Hirotaka

    2017-01-01

    Polymer-ceramic pressure-sensitive paint (PC-PSP) has been investigated as a surface-pressure sensor for unsteady aerodynamics and short duration measurements. This PSP provides a fast response to a change in pressures with a spray-coating ability. Because it is sprayed onto an aerodynamic surface, the thickness of PC-PSP may play an important role in determining the performance of this sensor. The thickness of other fast PSPs, such as anodized aluminum pressure-sensitive paint, is a major factor in determining its performance. We vary the thickness of PC-PSP from 10 to 240 μm in order to study its effects on PSP measurement characteristics including time response, signal level, pressure sensitivity, and temperature dependency. It is found that the thickness does affect these characteristics. However, a thickness over 80 μm provides uniform performance in these characteristics. PMID:28505122

  2. Residual Stress and Bonding Strength in the ElectricalSialon Ceramics Joint Made by Using the Brazing Metal Layer

    OpenAIRE

    Kimura, Mitsuhiko; Asari, Koichi; Goto, Shoji; Aso, Setsuo

    2002-01-01

    Electrical Sialons which have some TiN contents were joined with Ag-Cu-Ti active brazing metal layer having a thickness from 30μm to 400μm at a temperature from 1113 K to 1213 K in a vacuum. Residual stress in the brazed joint specimens was not observed when the thickness of brazing metal layer was 30 μ m. However, the residual stress of 80 MPa was detected when the thickness of brazing metal layer increased up to 400μm. When the brazing temperature was 1113 K, four-point bending strengths of...

  3. Incorporation of RANKL promotes osteoclast formation and osteoclast activity on β-TCP ceramics.

    Science.gov (United States)

    Choy, John; Albers, Christoph E; Siebenrock, Klaus A; Dolder, Silvia; Hofstetter, Wilhelm; Klenke, Frank M

    2014-12-01

    β-Tricalcium phosphate (β-TCP) ceramics are approved for the repair of osseous defects. In large defects, however, the substitution of the material by authentic bone is inadequate to provide sufficient long-term mechanical stability. We aimed to develop composites of β-TCP ceramics and receptor activator of nuclear factor κ-B ligand (RANKL) to enhance the formation of osteoclasts and promote cell mediated calcium phosphate resorption. RANKL was adsorbed superficially onto β-TCP ceramics or incorporated into a crystalline layer of calcium phosphate by the use of a co-precipitation technique. Murine osteoclast precursors were seeded onto the ceramics. After 15 days, the formation of osteoclasts was quantified cytologically and colorimetrically with tartrate-resistant acidic phosphatase (TRAP) staining and TRAP activity measurements, respectively. Additionally, the expression of transcripts encoding the osteoclast gene products cathepsin K, calcitonin receptor, and of the sodium/hydrogen exchanger NHA2 were quantified by real-time PCR. The activity of newly formed osteoclasts was evaluated by means of a calcium phosphate resorption assay. Superficially adsorbed RANKL did not induce the formation of osteoclasts on β-TCP ceramics. When co-precipitated onto β-TCP ceramics RANKL supported the formation of mature osteoclasts. The development of osteoclast lineage cells was further confirmed by the increased expression of cathepsin K, calcitonin receptor, and NHA2. Incorporated RANKL stimulated the cells to resorb crystalline calcium phosphate. Our in vitro study shows that RANKL incorporated into β-TCP ceramics induces the formation of active, resorbing osteoclasts on the material surface. Once formed, osteoclasts mediate the release of RANKL thereby perpetuating their differentiation and activation. In vivo, the stimulation of osteoclast-mediated resorption may contribute to a coordinated sequence of material resorption and bone formation. Further in vivo studies

  4. Preparation of calcium phosphate glass-ceramics and their coating on titanium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Kasuga, T.; Nogami, M. [Nagoya Inst. of Tech. (Japan). Dept. of Materials Science and Engineering; Niinomi, M. [Toyohashi Univ. of Technology (Japan). Dept. of Production Systems Engineering

    2001-07-01

    Novel silica-free calcium phosphate glass-ceramics was prepared by heating a compact of 60CaO . 30P{sub 2}O{sub 5} . 3TiO{sub 2} . 7Na{sub 2}O glass powders. When powder-compacts of the glasses were heated at 850 C, they crystallized and subsequently sintered, resulting in glass-ceramics containing {beta}Ca{sub 3}(PO{sub 4}){sub 2} and {beta}-Ca{sub 2}P{sub 2}O{sub 7} crystalline phases. The glass-ceramics show relatively high mechanical strength of 100 {proportional_to} 120 MPa in bending and fracture toughness of K{sub IC} {approx} 1.9 MPa.m{sup 0.5}. Hydroxyapatite was formed newly on the surface of the glass-ceramic in simulated body fluid at 37 C. By heating a new type of titanium alloy (Ti-29Nb-13Ta-4.6Zr), on which the glass powders were placed, at 800 C in air, a glass-ceramic layer containing {beta}-Ca{sub 3}(PO{sub 4}){sub 2} crystal was found to be joined easily with the metal. The joining between the coating layer and the metal substrate is very strong in tensile bonding strength. (orig.)

  5. Effect of wollastonite ceramics and bioactive glass on the formation of a bonelike apatite layer on a cobalt base alloy.

    Science.gov (United States)

    Cortés, D A; Medina, A; Escobedo, J C; Escobedo, S; López, M A

    2004-08-01

    A biomimetic method was used to promote a bioactive surface on a cobalt base alloy (ASTM F-75). The metallic substrates were alkali treated and some of the samples were subsequently heat treated. The treated samples were immersed in simulated body fluid (SBF) on granular particles of either bioactive glass or wollastonite. For comparative purposes, no bioactive system was used in some tests. Three different methods were used for the immersion of the samples in SBF: 1) 21 days in SBF, 2) 21 days in 1.5 SBF, and 3) 7 days in SBF followed by 14 days in 1.5 SBF (re-immersion method). A bonelike apatite layer was formed on all the samples placed on wollastonite and bioactive glass particles. The morphology of the apatite layer formed by using the re-immersion method and wollastonite closely resembled the existing bioactive systems. No apatite layer was observed on the samples treated without bioactive material and soaked for 21 days in SBF or 1.5 SBF, apart from the substrates treated by using the re-immersion method. The heat treatment delayed the apatite formation in all the cases studied. Copyright 2004 Wiley Periodicals, Inc. J Biomed Mater Res 70A: 341-346, 2004

  6. Oxidant effect of La(NO{sub 3}){sub 3}·6H{sub 2}O solution on the crystalline characteristics of nanocrystalline ZrO{sub 2} films grown by atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Oh, Nam Khen [Graduate School of Energy Science and Technology, Chungnam National University, 99 Daehak-ro, Yuseong-gu, Daejeon 34134 (Korea, Republic of); Vacuum Center, Korea Research Institute of Standards and Science (KRISS), 267 Gajeong-ro, Yuseong-gu, Daejeon 34113 (Korea, Republic of); Kim, Jin-Tae [Vacuum Center, Korea Research Institute of Standards and Science (KRISS), 267 Gajeong-ro, Yuseong-gu, Daejeon 34113 (Korea, Republic of); Department of Nanomaterials Science and Engineering, University of Science and Technology, 217 Gajeong-ro, Yuseong-gu, Daejeon 34113 (Korea, Republic of); Kang, Goru; An, Jong-Ki; Nam, Minwoo [Vacuum Center, Korea Research Institute of Standards and Science (KRISS), 267 Gajeong-ro, Yuseong-gu, Daejeon 34113 (Korea, Republic of); Kim, So Yeon [Graduate School of Energy Science and Technology, Chungnam National University, 99 Daehak-ro, Yuseong-gu, Daejeon 34134 (Korea, Republic of); Park, In-Sung, E-mail: parkis77@hanyang.ac.kr [Institute of Nano Science and Technology, Hanyang University, 222 Wangsimni-ro, Seongdong-gu, Seoul 04763 (Korea, Republic of); Yun, Ju-Young, E-mail: jyun@kriss.re.kr [Vacuum Center, Korea Research Institute of Standards and Science (KRISS), 267 Gajeong-ro, Yuseong-gu, Daejeon 34113 (Korea, Republic of); Department of Nanomaterials Science and Engineering, University of Science and Technology, 217 Gajeong-ro, Yuseong-gu, Daejeon 34113 (Korea, Republic of)

    2017-02-01

    Highlights: • The La(NO{sub 3}){sub 3}·6H{sub 2}O aqua solution is introduced as an oxidant in ALD process. • The H{sub 2}O and La(NO{sub 3}){sub 3}·6H{sub 2}O lead different crystalline properties of ZrO{sub 2} films. • Concentration of La(NO{sub 3}){sub 3}·6H{sub 2}O solution minimally influences crystalline status. - Abstract: Nanocrystalline ZrO{sub 2} films were synthesized by atomic layer deposition method using CpZr[N(CH{sub 3}){sub 2}]{sub 3} (Cp = C{sub 5}H{sub 5}) as the metal precursor and La(NO{sub 3}){sub 3}·6H{sub 2}O solution as the oxygen source. La element in the deposited ZrO{sub 2} films could not be detected as its content was below the resolution limit of the X-ray photoelectron spectroscopy. The alternative introduction of La(NO{sub 3}){sub 3}·6H{sub 2}O solution to conventionally used H{sub 2}O as the oxidant effectively altered the crystalline structure, grain size, and surface roughness of the grown ZrO{sub 2} films. Specifically, the crystalline structure of the ZrO{sub 2} film changed from a mixture of tetragonal and monoclinic phases to monoclinic phase. The average grain size also increased, and the resulting film surface became rougher. The average grain sizes of the ZrO{sub 2} films prepared from La(NO{sub 3}){sub 3}·6H{sub 2}O solution at concentrations of 10, 20, 30, and 40% were 280, 256, 208, and 200 nm, respectively, whereas that prepared using H{sub 2}O oxidant was 142 nm. However, the concentration of La(NO{sub 3}){sub 3}·6H{sub 2}O solution minimally influenced the crystalline characteristics of the nanocrystalline ZrO{sub 2} films i.e., the crystalline structure, grain size, and surface roughness except for crystallite size.

  7. 2D photonic crystal layer assisted thiosilicate ceramic plate with red-emitting film for high quality w -LEDs

    Energy Technology Data Exchange (ETDEWEB)

    Dai, Wubin; Lei, Yifeng; Zhou, Jia; Zhao, Yan; Zheng, Yunhao; Xu, Man; Wang, Shulin; Shen, Fan (Wuhan)

    2017-07-05

    In this work, we have succeeded in obtaining high quality warm w-light-emitting-diodes (LEDs) by adopting hybrid two-dimensional (2D) structure of SiNx photonic crystal layer (PCL) assisted cyan-emitting ceramic-plate thiosilicate SrLa2Si2S8:Ce3+ with red-emitting film SrLiAl3N4:Eu2+ phosphor on a 430 nm blue LED chip at 350 mA. 2D SiNx PCL was capped with thiosilicate is because it can enhance the luminous efficacy and maintain the low correlated color temperature (CCT) and high color-rendering index (CRI). High luminous efficacy (82.3 lm/W), high special CRI (R9=75) as well as the low CCT (5431 K) of the optimal w-LED was obtained due to the assistances of 2D SiNx PCL and narrow-band red-emitting phosphor with the doping percentage at 10 wt%. The synthesis processes, structural analysis, optical properties and LED device performances were detailed investigated to find out the relationship between the optimum composition and good optical properties. Based on intriguing luminescence properties by the 2D SiNx PCL and red-emitting film phosphor introducing, we proclaim this method could also have high potential application in other phosphor-converted w-LEDs.

  8. Realizing a facile and environmental-friendly fabrication of high-performance multi-crystalline silicon solar cells by employing ZnO nanostructures and an Al2O3 passivation layer.

    Science.gov (United States)

    Chen, Hong-Yan; Lu, Hong-Liang; Sun, Long; Ren, Qing-Hua; Zhang, Hao; Ji, Xin-Ming; Liu, Wen-Jun; Ding, Shi-Jin; Yang, Xiao-Feng; Zhang, David Wei

    2016-12-07

    Nowadays, the multi-crystalline silicon (mc-Si) solar cells dominate the photovoltaic industry. However, the current acid etching method on mc-Si surface used by firms can hardly suppress the average reflectance value below 25% in the visible light spectrum. Meanwhile, the nitric acid and the hydrofluoric contained in the etching solution is both environmental unfriendly and highly toxic to human. Here, a mc-Si solar cell based on ZnO nanostructures and an Al2O3 spacer layer is demonstrated. The eco-friendly fabrication is realized by low temperature atomic layer deposition of Al2O3 layer as well as ZnO seed layer. Moreover, the ZnO nanostructures are prepared by nontoxic and low cost hydro-thermal growth process. Results show that the best passivation quality of the n+ -type mc-Si surface can be achieved by balancing the Si dangling bond saturation level and the negative charge concentration in the Al2O3 film. Moreover, the average reflectance on cell surface can be suppressed to 8.2% in 400-900 nm range by controlling the thickness of ZnO seed layer. With these two combined refinements, a maximum solar cell efficiency of 15.8% is obtained eventually. This work offer a facile way to realize the environmental friendly fabrication of high performance mc-Si solar cells.

  9. Realizing a facile and environmental-friendly fabrication of high-performance multi-crystalline silicon solar cells by employing ZnO nanostructures and an Al2O3 passivation layer

    Science.gov (United States)

    Chen, Hong-Yan; Lu, Hong-Liang; Sun, Long; Ren, Qing-Hua; Zhang, Hao; Ji, Xin-Ming; Liu, Wen-Jun; Ding, Shi-Jin; Yang, Xiao-Feng; Zhang, David Wei

    2016-12-01

    Nowadays, the multi-crystalline silicon (mc-Si) solar cells dominate the photovoltaic industry. However, the current acid etching method on mc-Si surface used by firms can hardly suppress the average reflectance value below 25% in the visible light spectrum. Meanwhile, the nitric acid and the hydrofluoric contained in the etching solution is both environmental unfriendly and highly toxic to human. Here, a mc-Si solar cell based on ZnO nanostructures and an Al2O3 spacer layer is demonstrated. The eco-friendly fabrication is realized by low temperature atomic layer deposition of Al2O3 layer as well as ZnO seed layer. Moreover, the ZnO nanostructures are prepared by nontoxic and low cost hydro-thermal growth process. Results show that the best passivation quality of the n+ -type mc-Si surface can be achieved by balancing the Si dangling bond saturation level and the negative charge concentration in the Al2O3 film. Moreover, the average reflectance on cell surface can be suppressed to 8.2% in 400-900 nm range by controlling the thickness of ZnO seed layer. With these two combined refinements, a maximum solar cell efficiency of 15.8% is obtained eventually. This work offer a facile way to realize the environmental friendly fabrication of high performance mc-Si solar cells.

  10. A.C. Conductivity Investigations on Layered Na2-x-yLixKyTi3O7 Ceramics

    Directory of Open Access Journals (Sweden)

    Rakesh Singh

    2013-01-01

    Full Text Available Frequency and temperature dependence of a.c. electrical conductivity of layered mixed ionic alkali trititanates, Na1.89Li0.10K0.01Ti3O7, Na1.88Li0.10K0.02Ti3O7, Na1.86Li0.10K0.04Ti3O7, and Na1.85Li0.10K0.05Ti3O7, have been investigated over a wide temperature 350 K ≤T≥ 725 K and frequency 10 kHz to 1 MHz range. For this, Arrhenius plots are used for a.c. electrical conductivity of these compounds. The obtained conductivity plots have been divided into four distinct regions and discussed the relevant theory. According to slop variation, the conduction mechanisms occurring are different in different temperature regions. At lower temperatures, the hopping electron disorders the surroundings by moving to its neighboring Ti atoms from their equilibrium positions, causing structural defect in the polycrystalline network named small polaron. At higher temperatures, associated/unassociated interlayer ionic conduction occurs along with the alkali ions hopping through the interlayer space and electron hopping (small polaron conduction through Ti–Ti chains in these layered polar alkali titanates.

  11. A Spray Pyrolysis Method to Grow Carbon Nanotubes on Carbon Fibres, Steel and Ceramic Bricks.

    Science.gov (United States)

    Vilatela, Juan J; Rabanal, M E; Cervantes-Sodi, Felipe; García-Ruiz, Máximo; Jiménez-Rodríguez, José A; Reiband, Gerd; Terrones, Mauricio

    2015-04-01

    We demonstrate a spray pyrolysis method to grow carbon nanotubes (CNTs) with high degree of crystallinity, aspect ratio and degree of alignment on a variety of different substrates, such as conventional steel, carbon fibres (CF) and ceramics. The process consists in the chemical vapour deposition of both a thin SiO2 layer and CNTs that subsequently grow on this thin layer. After CNT growth, increases in specific surface by factors of 1000 and 30 for the steel and CF samples, respectively, are observed. CNTs growth on ceramic surfaces results in a surface resistance of 37.5 Ohm/sq. When using conventional steel as a rector tube, we observed CNTs growth rates of 0.6 g/min. Details of nanotube morphology and the growth mechanism are discussed. Since the method discussed here is highly versatile, it opens up a wide variety of applications in which specific substrates could be used in combination with CNTs.

  12. Process for making ceramic hot gas filter

    Science.gov (United States)

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

    2001-01-01

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

  13. Ceramic substrate including thin film multilayer surface conductor

    Science.gov (United States)

    Wolf, Joseph Ambrose; Peterson, Kenneth A.

    2017-05-09

    A ceramic substrate comprises a plurality of ceramic sheets, a plurality of inner conductive layers, a plurality of vias, and an upper conductive layer. The ceramic sheets are stacked one on top of another and include a top ceramic sheet. The inner conductive layers include electrically conductive material that forms electrically conductive features on an upper surface of each ceramic sheet excluding the top ceramic sheet. The vias are formed in each of the ceramic sheets with each via being filled with electrically conductive material. The upper conductive layer includes electrically conductive material that forms electrically conductive features on an upper surface of the top ceramic sheet. The upper conductive layer is constructed from a stack of four sublayers. A first sublayer is formed from titanium. A second sublayer is formed from copper. A third sublayer is formed from platinum. A fourth sublayer is formed from gold.

  14. Soft x-ray photoemission spectroscopy of the Ba atomic layer deposition on the ceramic multiferroic BiFeO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Benemanskaya, G.V., E-mail: galina.benemanskaya@mail.ioffe.ru [Ioffe Institute, Politekhnicheskaya str. 26, St. Petersburg, 194021 (Russian Federation); Dementev, P.A.; Lapushkin, M.N. [Ioffe Institute, Politekhnicheskaya str. 26, St. Petersburg, 194021 (Russian Federation); Timoshnev, S.N. [St Petersburg Academic University, Khlopina str.8/3, St. Petersburg, 194021 (Russian Federation); Senkovskiy, B. [Helmholts-Zentrum Berlin, Elektronenspeicherring BESSY II, Albert-Einstein-Strasse 15, D-12489 Berlin (Germany)

    2017-04-01

    Highlights: • Ba/BiFeO{sub 3} interface was studied by X-ray synchrotron- photoemission spectroscopy. • Ba adsorption is found to modify the Bi 4f, O 1s and Fe 2p core level spectra. • Ba induced charge transfer causes increasing in Bi-valency and O-ionicity. • Ba adsorption results in increasing the amount of Fe{sup 2+} ions in the surface region. - Abstract: Electronic structure of the ceramic multiferroic BiFeO{sub 3} and the Ba/BiFeO{sub 3} nanointerface is investigated in situ in an ultrahigh vacuum by synchrotron-based photoemission spectroscopy with the excited photon energy from 120 eV to 900 eV. The Bi 4f, O 1s, Fe 2p, and Ba 5p core-levels spectra are studied. The Ba atomic layer deposition is found to induce a significant change in spectra that is originated from the charge transfer between Ba adatoms and Bi, O surface atoms with increasing the Bi-valency and O-ionicity. The Fe 2p{sub 3/2} core level spectrum for the clean BiFeO{sub 3} is shown to contain both the Fe{sup 2+} and Fe{sup 3+} ion components with the atomic ratio of Fe{sup 2+}/Fe{sup 3+} ∼1. The Ba adsorption is found to increase the ratio up to ∼1.5. This new effect is clearly caused by recharge between Fe{sup 3+} ↔ Fe{sup 2+} ions with increasing the amount of Fe{sup 2+} ions.

  15. Thick ceramic coating technique. Atsuniku ceramic coating gijutsu

    Energy Technology Data Exchange (ETDEWEB)

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

    1987-10-15

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

  16. Assessment of nickel oxide substituted bioactive glass-ceramic on in vitro bioactivity and mechanical properties

    Energy Technology Data Exchange (ETDEWEB)

    Kumar Vyas, V.; Sampath Kumar, A.; Ali, A.; Prasad, S.; Srivastava, P.; Prasanna Mallick, S.; Ershad, Md.; Prasad Singh, S.; Pyare, R.

    2016-07-01

    Many type of oxide substituted glass-ceramics like strontium, cobalt, barium and titanium have shown bioactivity with improved mechanical properties. The present work reports the in vitro bioactivity and mechanical properties of nickel oxide substituted in bioactive glass-ceramic and results were compared with 45S5 bioactive glass-ceramic. Bioactive glass ceramics were processed through controlled crystallization of their respective bioactive glasses. The formed crystalline phases in bioactive glass-ceramics were identified using X-ray diffraction (XRD) analysis. The formation of HA layer was assessed by immersing them in the simulated body fluid (SBF) for different soaking periods. The formation of hydroxyapatite was confirmed by FTIR spectrometry, SEM and pH measurement. Densities and mechanical properties of the samples were found to increase considerably with an increasing the concentration of nickel oxide. A decrease in glass transition temperature (Tg) with NiO addition showed that the nickel oxide had acted as an intermediate in smaller quantities in the bioactive glass. The cell culture studies demonstrated that the samples containing low concentration of NiO from 0 to 1.65mol% were non-cytotoxic against osteoblast cells. Finally, this investigation clearly concluded that NiO doped bioactive glass would be potential biomaterials for biomedical applications. (Author)

  17. Characterization of some bioglass-ceramics

    Energy Technology Data Exchange (ETDEWEB)

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

    2003-06-26

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

  18. Impacts of amorphous and crystalline cobalt ferrite layers on the giant magneto-impedance response of a soft ferromagnetic amorphous ribbon

    Energy Technology Data Exchange (ETDEWEB)

    Mukherjee, D.; Devkota, J.; Ruiz, A.; Hordagoda, M.; Hyde, R.; Witanachchi, S.; Mukherjee, P.; Srikanth, H.; Phan, M. H., E-mail: phanm@usf.edu [Center for Integrated Functional Materials, Department of Physics, University of South Florida, Tampa, Florida 33620 (United States)

    2014-09-28

    A systematic study of the effect of depositing CoFe₂O₄ (CFO) films of various thicknesses (d = 0–600 nm) on the giant magneto-impedance (GMI) response of a soft ferromagnetic amorphous ribbon Co₆₅Fe₄Ni₂Si₁₅B₁₄ has been performed. The CFO films were grown on the amorphous ribbons by the pulsed laser deposition technique. X-ray diffraction and transmission electron microscopy revealed a structural variation of the CFO film from amorphous to polycrystalline as the thickness of the CFO film exceeded a critical value of 300 nm. Atomic force microscopy evidenced the increase in surface roughness of the CFO film as the thickness of the CFO film was increased. These changes in the crystallinity and morphology of the CFO film were found to have a distinct impact on the GMI response of the ribbon. Relative to the bare ribbon, coating of amorphous CFO films significantly enhanced the GMI response of the ribbon, while polycrystalline CFO films decreased it considerably. The maximum GMI response was achieved near the onset of the structural transition of the CFO film. These findings are of practical importance in developing high-sensitivity magnetic sensors.

  19. A micro-scale hot wire anemometer based on low stress (Ni/W) multi-layers deposited on nano-crystalline diamond for air flow sensing

    Science.gov (United States)

    Talbi, A.; Gimeno, L.; Gerbedoen, J.-C.; Viard, R.; Soltani, A.; Mortet, V.; Preobrazhensky, V.; Merlen, A.; Pernod, P.

    2015-12-01

    A linear array of microscale thermal anemometers has been designed, fabricated and characterized. The sensitive element consists of a self-compensated-stress multilayer (Ni/W) patterned to form a wire with length, width, and thickness close to 200 μm, 5 μm and 2 μm respectively. The wire is deposited and supported by prongs made of nano-crystalline diamond (NCD) of about 2 μm in thickness. Due to its high Young’s modulus, NCD allows a very high mechanical toughness without the need for thicker support for the hot wire. Also, depending on grain size, the NCD is able to present thermal conductivity smaller than 10 W mK-1, providing good thermal insulation from the substrate and less conductive end losses to the prongs. The sensor was characterized experimentally. Its electrical and thermal properties were obtained first in the absence of fluid flow. The results confirm the effectiveness of thermal insulation and the mechanical robustness of the structure. The fluidic characterizations were performed and analysed in the case of an airflow with velocities of up to 30 m s-1.

  20. Ceramic joining

    Energy Technology Data Exchange (ETDEWEB)

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

    1996-04-01

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

  1. 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.

  2. Method of making multilayered titanium ceramic composites

    Energy Technology Data Exchange (ETDEWEB)

    Fisher, George T., II; Hansen; Jeffrey S.; Oden; Laurance L.; Turner; Paul C.; Ochs; Thomas L.

    1998-08-25

    A method making a titanium ceramic composite involves forming a hot pressed powder body having a microstructure comprising at least one titanium metal or alloy layer and at least one ceramic particulate reinforced titanium metal or alloy layer and hot forging the hot pressed body follwed by hot rolling to substantially reduce a thickness dimension and substantially increase a lateral dimension thereof to form a composite plate or sheet that retains in the microstructure at least one titanium based layer and at least one ceramic reinforced titanium based layer in the thickness direction of the composite plate or sheet.

  3. THE THICKNESS DEPENDENCE OF OXYGEN PERMEABILITY IN SOL-GEL DERIVED CGO-COFE2O4 THIN FILMS ON POROUS CERAMIC SUBSTRATES: A SPUTTERED BLOCKING LAYER FOR THICKNESS CONTROL

    Energy Technology Data Exchange (ETDEWEB)

    Brinkman, K

    2009-01-08

    Mixed conductive oxides are a topic of interest for applications in oxygen separation membranes as well as use in producing hydrogen fuel through the partial oxidation of methane. The oxygen flux through the membrane is governed both by the oxygen ionic conductivity as well as the material's electronic conductivity; composite membranes like Ce{sub 0.8}Gd{sub 0.2}O{sub 2-{delta}} (CGO)-CoFe{sub 2}O{sub 4} (CFO) use gadolinium doped ceria oxides as the ionic conducting material combined with cobalt iron spinel which serves as the electronic conductor. In this study we employ {approx} 50 nm sputtered CeO{sub 2} layers on the surface of porous CGO ceramic substrates which serve as solution 'blocking' layers during the thin film fabrication process facilitating the control of film thickness. Films with thickness of {approx} 2 and 4 microns were prepared by depositing 40 and 95 separate sol-gel layers respectively. Oxygen flux measurements indicated that the permeation increased with decreasing membrane thickness; thin film membrane with thickness on the micron level showed flux values an order of magnitude greater (0.03 {micro}mol/cm{sup 2} s) at 800 C as compared to 1mm thick bulk ceramic membranes (0.003 {micro}mol/cm{sup 2}).

  4. Structure and electrical properties of intergrowth bismuth layer-structured Bi4Ti3O12-CaBi4Ti4O15 ferroelectric ceramics

    Science.gov (United States)

    Choi, Gi Ppeum; Cho, Sam Yeon; Bu, Sang Don

    2016-09-01

    Pb-free ferroelectric Bi4Ti3O12-CaBi4Ti4O15 (BIT-CBT) ceramics were manufactured using a solid-state reaction method. Structural analysis by using X-ray diffraction confirmed the presence of a second phase of Bi2Ti2O7, and the surface depth X-ray diffraction analysis revealed that this phase existed only on the surface. This second phase appears to have been caused by the volatilization of Bi ions at high sintering temperatures. For resolution of the issue of volatilization of Bi ions and manufacture of BIT-CBT ceramics with a single phase, Bi2O3 powder was added to the BIT-CBT mixture, and a powder-bed method, in which pellets were covered with BIT-CBT powder, was used to manufacture the ceramic. The piezoelectric coefficient of the single-phase BIT-CBT ceramics was 12.4 pC/N while the residual polarization and the coercive electric field were 11.3 μC/cm2, and 125 kV/cm, respectively. The results suggest that single-phase BIT-CBT ceramics are suitable for the manufacture of elements incorporating these electrical characteristics.

  5. Ceramics: Durability and radiation effects

    Energy Technology Data Exchange (ETDEWEB)

    Ewing, R.C.; Lutze, W. [Univ. of New Mexico, Albuquerque, NM (United States); Weber, W.J. [Pacific Northwest National Lab., Richland, WA (United States)

    1996-05-01

    At present, there are three seriously considered options for the disposition of excess weapons plutonium: (1) incorporation, partial burn-up and direct disposal of MOX-fuel; (2) vitrification with defense waste and disposal as glass {open_quotes}logs{close_quotes}; (3) deep borehole disposal. The first two options provide a safeguard due to the high activity of fission products in the irradiated fuel and the defense waste. The latter option has only been examined in a preliminary manner, and the exact form of the plutonium has not been identified. In this paper, we review the potential for the immobilization of plutonium in highly durable crystalline ceramics apatite, pyrochlore, zirconolite, monazite and zircon. Based on available data, we propose zircon as the preferred crystalline ceramic for the permanent disposition of excess weapons plutonium.

  6. [Ceramic posts].

    Science.gov (United States)

    Mainjot, Amélie; Legros, Caroline; Vanheusden, Alain

    2006-01-01

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

  7. Effect of crystalline structure of TiO{sub 2} substrates on initial growth of atomic layer deposited Ru thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Seong Keun; Han, Sora; Han, Jeong Hwan [WCU Hybrid Materials Program, Department of Materials Science and Engineering and Interuniversity, Semiconductor Research Center, Seoul National University, Seoul 151-744 (Korea, Republic of); Hwang, Cheol Seong, E-mail: cheolsh@snu.ac.kr [WCU Hybrid Materials Program, Department of Materials Science and Engineering and Interuniversity, Semiconductor Research Center, Seoul National University, Seoul 151-744 (Korea, Republic of)

    2011-02-15

    Ru thin films were grown on polymorphic TiO{sub 2} thin film substrates at 230 and 250 deg. C by atomic layer deposition using 2,4-(dimethylpentadienyl)(ethylcyclopentadienyl)Ru and an O{sub 2} gas. While the Ru films grown on amorphous and rutile TiO{sub 2} substrates showed a relatively long incubation cycle number of approximately 350 and 100 at 230 and 250 deg. C, respectively, the Ru films grown on anatase TiO{sub 2} substrates exhibited a significantly shorter incubation delay which was attributed to the catalytic activity of anatase TiO{sub 2}. This difference in the incubation cycle affected the surface morphology of the Ru films on different TiO{sub 2} substrates.

  8. In vitro apatite formation on nano-crystalline titania layer aligned parallel to Ti6Al4V alloy substrates with sub-millimeter gap.

    Science.gov (United States)

    Hayakawa, Satoshi; Matsumoto, Yuko; Uetsuki, Keita; Shirosaki, Yuki; Osaka, Akiyoshi

    2015-06-01

    Pure titanium substrates were chemically oxidized with H2O2 and subsequent thermally oxidized at 400 °C in air to form anatase-type titania layer on their surface. The chemically and thermally oxidized titanium substrate (CHT) was aligned parallel to the counter specimen such as commercially pure titanium (cpTi), titanium alloy (Ti6Al4V) popularly used as implant materials or Al substrate with 0.3-mm gap. Then, they were soaked in Kokubo's simulated body fluid (SBF, pH 7.4, 36.5 °C) for 7 days. XRD and SEM analysis showed that the in vitro apatite-forming ability of the contact surface of the CHT specimen decreased in the order: cpTi > Ti6Al4V > Al. EDX and XPS surface analysis showed that aluminum species were present on the contact surface of the CHT specimen aligned parallel to the counter specimen such as Ti6Al4V and Al. This result indicated that Ti6Al4V or Al specimens released the aluminum species into the SBF under the spatial gap. The released aluminum species might be positively or negatively charged in the SBF and thus can interact with calcium or phosphate species as well as titania layer, causing the suppression of the primary heterogeneous nucleation and growth of apatite on the contact surface of the CHT specimen under the spatial gap. The diffusion and adsorption of aluminum species derived from the half-sized counter specimen under the spatial gap resulted in two dimensionally area-selective deposition of apatite particles on the contact surfaces of the CHT specimen.

  9. Crystalline and Crystalline International Disposal Activities

    Energy Technology Data Exchange (ETDEWEB)

    Viswanathan, Hari S. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Chu, Shaoping [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Reimus, Paul William [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Makedonska, Nataliia [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Hyman, Jeffrey De' Haven [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Karra, Satish [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Dittrich, Timothy M. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-12-21

    This report presents the results of work conducted between September 2014 and July 2015 at Los Alamos National Laboratory in the crystalline disposal and crystalline international disposal work packages of the Used Fuel Disposition Campaign (UFDC) for DOE-NE’s Fuel Cycle Research and Development program.

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

    Energy Technology Data Exchange (ETDEWEB)

    Tortorelli, P.F.

    1996-06-01

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

  11. Tantalum-Based Ceramics for Refractory Composites

    Science.gov (United States)

    Stewart, David A.; Leiser, Daniel; DiFiore, Robert; Kalvala, Victor

    2006-01-01

    A family of tantalum-based ceramics has been invented as ingredients of high-temperature composite insulating tiles. These materials are suitable for coating and/or permeating the outer layers of rigid porous (foam-like or fibrous) ceramic substrates to (1) render the resulting composite ceramic tiles impervious to hot gases and (2) enable the tiles to survive high heat fluxes at temperatures that can exceed 3,000 F ( 1,600 C).

  12. Avaliação das fases cristalinas de dióxido de titânio suportado em cerâmica vermelha Evaluation of the crystalline phases of supported titanium dioxide in red ceramic

    Directory of Open Access Journals (Sweden)

    G. T Saleiro

    2010-06-01

    Full Text Available O dióxido de titânio apresenta boas propriedades como um material fotocatalisador para aplicação em processos de degradação fotocatalítica. No entanto, o dióxido de titânio deve ser usado ancorado num suporte adequado. O uso de cerâmica vermelha como suporte de fotocatalisadores pode ser uma boa alternativa devido ao seu baixo custo e facilidade de fabricação. Neste trabalho foi estudado, via difração de raios X, o dióxido de titânio suportado em cerâmica vermelha produzida com argilas cauliníticas da região de Campos dos Goytacazes, RJ. Os resultados mostram que o dióxido de titânio apresenta mudança estrutural da fase mais fotoativa (anatásio para a fase menos fotoativa (rutilo com o aumento da temperatura de sinterização. Em 700 ºC cerca de 50% da fase anatásio é retida para o dióxido de titânio suportado em cerâmica vermelha, independentemente do tipo de argila usada.The titanium dioxide presents good properties as a photocatalyst material for application in processes of photocatalytic degradation. However, the titanium dioxide should be anchored on a suitable support. The use of red ceramic as supporting material can be an alternative very interesting due to the its low cost and ease of manufacturing. In this work was studied via X-ray diffraction the phase transformation anatase-rutile at different temperatures for supported titanium dioxide in red ceramic substrate prepared with kaolinitic clays from the Campos dos Goytacazes-RJ region. The results showed that the effect of the sintering temperature was promoting the structural change of the phase more photoactive (anatase for the less photoactive (rutile. At 700 ºC about 50% of the anatase phase is retained for supported titanium dioxide in red ceramic substrate, independently of the clay type used.

  13. Amorphous silicon oxide layers for surface passivation and contacting of heterostructure solar cells of amorphous and crystalline silicon; Amorphe Siliziumoxidschichten zur Oberflaechenpassivierung und Kontaktierung von Heterostruktur-Solarzellen aus amorphen und kristallinem Silizium

    Energy Technology Data Exchange (ETDEWEB)

    Einsele, Florian

    2010-02-05

    Atomic hydrogen plays a dominant role in the passivation of crystalline silicon surfaces by layers of amorphous silicon. In order to research into this role, this thesis presents the method of hydrogen effusion from thin amorphous films of silicon (a-Si:H) and silicon oxide (a-SiO{sub x}:H). The oxygen concentration of the sub-stoichiometric a-SiO{sub x}:H films ranges up to 10 at.-%. The effusion experiment yields information about the content and thermal stability of hydrogen and about the microstructure of the films. A mathematical description of the diffusion process of atomic hydrogen yields an analytical expression of the effusion rate R{sub E} depending on the linearly increasing temperature in the experiment. Fitting of the calculated effusion rates R{sub E} to measured effusion spectra yields the diffusion coefficient of atomic hydrogen in a-SiO{sub x}:H. With increasing oxygen concentration, the diffusion coefficient of hydrogen in the a-SiO{sub x}:H films decreases. This is attributed to an increasing Si-H bond energy due to back bonded oxygen, resulting in a higher stability of hydrogen in the films. This result is confirmed by an increasing thermal stability of the p-type c-Si passivation with a-SiO{sub x}:H of increasing oxygen concentrations up to 5 at.-%. The passivation reaches very low recombination velocities of S < 10 cm/s at the interface. However, for higher oxygen concentrations up to 10 at.-%, the passivation quality decreases significantly. Here, infrared spectroscopy of Si-H vibrational modes and hydrogen effusion show an increase of hydrogen-rich interconnected voids in the films. This microstructure results in a high amount of molecular hydrogen (H{sub 2}) in the layers, which is not suitable for the saturation of c-Si interface defects. Annealing of the films at temperatures around 400 C leads to a release of H{sub 2} from the voids, as a result of which Si-Si bonds in the material reconstruct. Subsequently, hydrogen migration in the

  14. Engineering ceramics

    CERN Document Server

    Bengisu, Murat

    2001-01-01

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

  15. EFFECT OF NANOPOWDER ADDITION ON THE FLEXURAL STRENGTH OF ALUMINA CERAMIC - A WEIBULL MODEL ANALYSIS

    OpenAIRE

    Daidong Guo; Shiquan Liu

    2016-01-01

    Alumina ceramics were prepared either with micrometer-sized alumina powder (MAP) or with the addition of nanometer-sized alumina powder (NAP). The density, crystalline phase, flexural strength and the fracture surface of the two ceramics were measured and compared. Emphasis has been put on the influence of nanopowder addition on the flexural strength of Al₂O₃ ceramic. The analysis based on the Weibull distribution model suggests the distribution of the flexural strength of the NAP ceramic is ...

  16. Biaxial flexural strength of bilayered zirconia using various veneering ceramics

    OpenAIRE

    Chantranikul, Natravee; Salimee, Prarom

    2015-01-01

    PURPOSE The aim of this study was to evaluate the biaxial flexural strength (BFS) of one zirconia-based ceramic used with various veneering ceramics. MATERIALS AND METHODS Zirconia core material (Katana) and five veneering ceramics (Cerabien ZR; CZR, Lava Ceram; LV, Cercon Ceram Kiss; CC, IPS e.max Ceram; EM and VITA VM9; VT) were selected. Using the powder/liquid layering technique, bilayered disk specimens (diameter: 12.50 mm, thickness: 1.50 mm) were prepared to follow ISO standard 6872:20...

  17. Nano-Ceramic Coated Plastics

    Science.gov (United States)

    Cho, Junghyun

    2013-01-01

    Plastic products, due to their durability, safety, and low manufacturing cost, are now rapidly replacing cookware items traditionally made of glass and ceramics. Despite this trend, some still prefer relatively expensive and more fragile ceramic/glassware because plastics can deteriorate over time after exposure to foods, which can generate odors, bad appearance, and/or color change. Nano-ceramic coatings can eliminate these drawbacks while still retaining the advantages of the plastic, since the coating only alters the surface of the plastic. The surface coating adds functionality to the plastics such as self-cleaning and disinfectant capabilities that result from a photocatalytic effect of certain ceramic systems. These ceramic coatings can also provide non-stick surfaces and higher temperature capabilities for the base plastics without resorting to ceramic or glass materials. Titanium dioxide (TiO2) and zinc oxide (ZnO) are the candidates for a nano-ceramic coating to deposit on the plastics or plastic films used in cookware and kitchenware. Both are wide-bandgap semiconductors (3.0 to 3.2 eV for TiO2 and 3.2 to 3.3 eV for ZnO), so they exhibit a photocatalytic property under ultraviolet (UV) light. This will lead to decomposition of organic compounds. Decomposed products can be easily washed off by water, so the use of detergents will be minimal. High-crystalline film with large surface area for the reaction is essential to guarantee good photocatalytic performance of these oxides. Low-temperature processing (plastics. One possible way of processing nanoceramic coatings at low temperatures (plastic materials (silicone, Teflon, PET, etc.) that can possess both photocatalytic oxide properties and flexible plastic properties. Processing cost is low and it does not require any expensive equipment investment. Processing can be scalable to current manufacturing infrastructure.

  18. EFFECT OF NANOPOWDER ADDITION ON THE FLEXURAL STRENGTH OF ALUMINA CERAMIC - A WEIBULL MODEL ANALYSIS

    Directory of Open Access Journals (Sweden)

    Daidong Guo

    2016-05-01

    Full Text Available Alumina ceramics were prepared either with micrometer-sized alumina powder (MAP or with the addition of nanometer-sized alumina powder (NAP. The density, crystalline phase, flexural strength and the fracture surface of the two ceramics were measured and compared. Emphasis has been put on the influence of nanopowder addition on the flexural strength of Al₂O₃ ceramic. The analysis based on the Weibull distribution model suggests the distribution of the flexural strength of the NAP ceramic is more concentrated than that of the MAP ceramic. Therefore, the NAP ceramics will be more stable and reliable in real applications.

  19. Ceramic-Metal Interfaces in Multilayer Actuators

    DEFF Research Database (Denmark)

    Engell, John; Pedersen, Henrik Guldberg; Andersen, Bjørn

    1996-01-01

    on the quality and strength of this interface. In the case of a weak ceramic-metal interface, delaminations will occur under severe working conditions.Work has been carried out on a commercial PZT type ceramic and various types of Pt electrode paste. The present study involves characterization of the interface......Multilayer actuators consist of a number of piezoelectric or electrostrictive ceramic layers, separated by thin metal electrodes. Thus, the ceramic-metal interface plays an even more important role than for bulk piezoceramics. The performance and durability of the actuator depends closely...

  20. Bioactive glass 45S5 powders: effect of synthesis route and resultant surface chemistry and crystallinity on protein adsorption from human plasma.

    Science.gov (United States)

    Bahniuk, Markian S; Pirayesh, Hamidreza; Singh, Harsh D; Nychka, John A; Unsworth, Larry D

    2012-12-01

    Despite its medical applications, the mechanisms responsible for the osseointegration of bioactive glass (45S5) have yet to be fully understood. Evidence suggests that the strongest predictor for osseointegration of bioactive glasses, and ceramics, with bone tissue as the formation of an apatitic calcium phosphate layer atop the implanted material, with osteoblasts being the main mediator for new bone formation. Most have tried to understand the formation of this apatitic calcium phosphate layer, and other bioresponses between the host and bioactive glass 45S5 using Simulated Body Fluid; a solution containing ion concentrations similar to that found in human plasma without the presence of proteins. However, it is likely that cell attachment is probably largely mediated via the adsorbed protein layer. Plasma protein adsorption at the tissue bioactive glass interface has been largely overlooked. Herein, we compare crystalline and amorphous bioactive glass 45S5, in both melt-derived as well as sol-gel forms. Thus, allowing for a detailed understanding of both the role of crystallinity and powder morphology on surface ions, and plasma protein adsorption. It was found that sol-gel 45S5 powders, regardless of crystallinity, adsorbed 3-5 times as much protein as the crystalline melt-derived counterpart, as well as a greater variety of plasma proteins. The devitrification of melt-cast 45S5 resulted in only small differences in the amount and variety of the adsorbed proteome. Surface properties, and not material crystallinity, play a role in directing protein adsorption phenomena for bioactive glasses given the differences found between crystalline melt-cast 45S5 and sol-gel derived 45S5.

  1. Influence of microstructure on electromechanical properties of nano-crystalline La-Pb(Ni{sub 1/3}Sb{sub 2/3})-PbZrTiO{sub 3} ferroelectric ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, H.H.; Lonkar, C.M. [Armament Research and Development Establishment, Pune (India); Balasubramanian, K. [Defence Institute of Advanced Technology (Deemed University), Pune (India)

    2017-10-15

    A ferroelectric ceramic composition, Pb{sub 0.98}La{sub 0.02}(Ni{sub 1/3}Sb{sub 2/3}){sub 0.05}[(Zr{sub 0.52}Ti{sub 0.48}){sub 0.995}] {sub 0.95}O{sub 3}, has been synthesized by columbite precursor method followed by mechanical activation for 10 h (MA-10) using high-energy ball mill. Formation of desired perovskite phase during activation was confirmed from analysis of X-ray diffraction patterns, while powder particle size, in nano-meter range, was revealed from high-resolution transmission electron microscopic (HRTEM) investigations. Samples were sintered between 1170 and 1320 C, and were investigated for microstructure and its influence on electromechanical properties. Increment in grain size with sintering temperature was noticed. 1220 C sintering temperature posed denser and uniform microstructure amongst all the temperatures and also showed composition close to morphotropic phase boundary (MPB) of PZT with optimum tetragonality which resulted in better electromechanical properties, suggesting the suitability of this composition for power harvesting applications. Phase transition studies revealed normal ferroelectric behaviour with transition temperature of 286 C. (orig.)

  2. Bioactivity and cytotoxicity of glass and glass-ceramics based on the 3CaO·P₂O₅--SiO₂--MgO system.

    Science.gov (United States)

    Daguano, Juliana K M F; Rogero, Sizue O; Crovace, Murilo C; Peitl, Oscar; Strecker, Kurt; Dos Santos, Claudinei

    2013-09-01

    The mechanical strength of bioactive glasses can be improved by controlled crystallization, turning its use as bulk bone implants viable. However, crystallization may affect the bioactivity of the material. The aim of this study was to develop glass-ceramics of the nominal composition (wt%) 52.75(3CaO·P₂O₅)-30SiO₂-17.25MgO, with different crystallized fractions and to evaluate their in vitro cytotoxicity and bioactivity. Specimens were heat-treated at 700, 775 and 975 °C, for 4 h. The major crystalline phase identified was whitlockite, an Mg-substituted tricalcium phosphate. The evaluation of the cytotoxicity was carried out by the neutral red uptake methodology. Ionic exchanges with the simulated body fluid SBF-K9 acellular solution during the in vitro bioactivity tests highlight the differences in terms of chemical reactivity between the glass and the glass-ceramics. The effect of crystallinity on the rates of hydroxycarbonate apatite (HCA) formation was followed by Fourier transformed infrared spectroscopy. Although all glass-ceramics can be considered bioactive, the glass-ceramic heat-treated at 775 °C (V775-4) presented the most interesting result, because the onset for HCA formation is at about 24 h and after 7 days the HCA layer dominates completely the spectrum. This occurs probably due to the presence of the whitlockite phase (3(Ca,Mg)O·P₂O₅). All samples were considered not cytotoxic.

  3. Development of nano-macroporous soda-lime phosphofluorosilicate bioactive glass and glass-ceramics.

    Science.gov (United States)

    Moawad, H M M; Jain, H

    2009-07-01

    We have extended the usefulness of bioactive glass-ceramics for the repair and reconstruction of hard tissues by introducing F ions that are known to be beneficial, especially in dentistry. Nano-macro multimodal porosity in soda-lime phosphofluorosilicate bulk samples was introduced by the recently developed melt-quench-heat-etch method. The choice of starting glass composition is based on 48SiO2-2.7P2O5-xCaF2-yCaO-zNa2O where x = 0, 1, 4, 8, 10, 12, and (y + z) = 49.3-x (mol%). The effect of thermal and chemical treatment on the microstructure of samples is characterized by SEM, XRD and EDX. We find the formation of many crystalline phases, but mainly sodium calcium silicate, calcium phosphate, fluorapatite and calcium silicate. The bioactivity of soda-lime phosphofluorosilicate glass-ceramics is assessed by monitoring the formation of hydroxyl apatite (HA) layer: fluorapatite phase accelerates the rate of HA layer formation; the initial composition and multi-modal porosity are other key parameters that impact the formation of HA. The present porous glass-ceramics should be superior candidates for use in dental bone regeneration.

  4. Evaluating the Type of Light Transmittance in Mono Crystalline, Poly Crystalline and Sapphire Brackets- An Invitro Spectrofluorometer Study.

    Science.gov (United States)

    Mohamed, Jauhar P; Kommi, Pradeep Babu; Kumar, M Senthil; Hanumanth; Venkatesan; Aniruddh; Arvinth; Kumar, Arani Nanda

    2016-08-01

    Most of the patients seek orthodontic treatment to improve the smile, which improves the facial profile by means of fixed appliances i.e., brackets and wires. The brackets are of different types like stainless steel and ceramic. Ceramic brackets were considered as aesthetic appliance which was divided into mono-crystalline, polycrystalline and sapphire brackets. The light transmittance might influence the degree of curing adhesive material in mono crystalline, polycrystalline and sapphire brackets. The aim of the present study was to evaluate the translucency and intensity of three different aesthetic brackets (mono crystalline, poly crystalline and sapphire ceramic brackets) and to determine their influence on shear bond strength of the brackets. The adhesive remnant index was also measured after debonding of the brackets from the tooth surface. Twenty six samples each of monocrystalline, polycrystalline and sapphire brackets (total 78 ceramic brackets) were used for the study. The bracket samples were subjected to optical fluorescence test using spectrofluorometer to measure the intensity of the brackets. Seventy eight extracted premolar teeth were procured and divided into 3 groups. The brackets were then bonded to the tooth using Transbond XT (3M Unitek) light cure composite material and cured with new light cure unit (Light Emitting Diode) of wood pecker company (400-450nm) for 30 seconds, and these samples were subjected to shear bond strength test with Instron Universal Testing Machine (UNITEK-94100) with a load range between 0 to 100 KN with a maximum cross head speed of 0.5mm/min. ARI (Adhesive Remnant Index) scores were evaluated according to Artun and Bergland scoring system using stereomicroscope at 20x magnification. The light absorption values obtained from spectrofluorometeric study were 3300000-3500000 cps for group 1 (monocrystalline ceramic brackets), 6000000-6500000 cps for Group 2 (polycrystalline ceramic brackets) and 2700000 -3000000 cps for

  5. Crystalline and Crystalline International Disposal Activities

    Energy Technology Data Exchange (ETDEWEB)

    Viswanathan, Hari S. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Chu, Shaoping [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Dittrich, Timothy M. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Hyman, Jeffrey De' Haven [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Karra, Satish [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Makedonska, Nataliia [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Reimus, Paul William [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-03-06

    This report presents the results of work conducted between September 2015 and July 2016 at Los Alamos National Laboratory in the crystalline disposal and crystalline international disposal work packages of the Used Fuel Disposition Campaign (UFDC) for DOE-NE’s Fuel Cycle Research and Development program. Los Alamos focused on two main activities during this period: Discrete fracture network (DFN) modeling to describe flow and radionuclide transport in complex fracture networks that are typical of crystalline rock environments, and a comprehensive interpretation of three different colloid-facilitated radionuclide transport experiments conducted in a fractured granodiorite at the Grimsel Test Site in Switzerland between 2002 and 2013. Chapter 1 presents the results of the DFN work and is divided into three main sections: (1) we show results of our recent study on the correlation between fracture size and fracture transmissivity (2) we present an analysis and visualization prototype using the concept of a flow topology graph for characterization of discrete fracture networks, and (3) we describe the Crystalline International work in support of the Swedish Task Force. Chapter 2 presents interpretation of the colloidfacilitated radionuclide transport experiments in the crystalline rock at the Grimsel Test Site.

  6. Study of clay chemical composition in formation of new phases in crystalline materials ceramic; Estudo da composicao quimica de argilas na formacao de novas fases cristalinas em materiais ceramicos

    Energy Technology Data Exchange (ETDEWEB)

    Lima, L.K.S.; Goncalves, W.P.; Silva, V.J.; Dias, G.; Neves, G.A.; Santana, L.N.L., E-mail: lizandralima15@gmail.com, E-mail: lisiane@dema.ufcg.edu.br [Universidade Federal de Campina Grande (UFCG), PB (Brazil). Unidade Academica de Engenharia dos Materiais

    2016-07-01

    The knowledge of the characteristics of raw materials and the behavior of these during the heat treatment is crucial before starting any manufacturing process of clay-based products. The objective of this work was to study phase transformations of clay under different heat treatments using conventional oven. To achieve the same were used two clays coming from the municipality of Cubati - PB and kaolin from an industry in the Northeast. The samples were subjected to beneficiation process, crushing, grinding and sieving and further characterized: chemical analysis, particle size, thermal and mineralogical. For heat treatment temperatures employed were 1000, 1100 and 1200 ° C, heating rate 5 ° C / min and residence time of 60min. After this step, the mineralogical characterization was performed by x-ray diffraction technique. Clays with larger particle size fraction below 2um and greater amount of flux oxides showed higher amount of mullite for the temperatures studied. The results also showed nucleation of mullite phase from 1100 °C, a band 2theta in the range of between 20 and 25°, characteristic of amorphous silica and the temperature rise was observed intensification of crystalline phases. (author)

  7. Crystalline Silica Primer

    Science.gov (United States)

    ,

    1992-01-01

    Crystalline silica is the scientific name for a group of minerals composed of silicon and oxygen. The term crystalline refers to the fact that the oxygen and silicon atoms are arranged in a threedimensional repeating pattern. This group of minerals has shaped human history since the beginning of civilization. From the sand used for making glass to the piezoelectric quartz crystals used in advanced communication systems, crystalline silica has been a part of our technological development. Crystalline silica's pervasiveness in our technology is matched only by its abundance in nature. It's found in samples from every geologic era and from every location around the globe. Scientists have known for decades that prolonged and excessive exposure to crystalline silica dust in mining environments can cause silicosis, a noncancerous lung disease. During the 1980's, studies were conducted that suggested that crystalline silica also was a carcinogen. As a result of these findings, crystalline silica has been regulated under the Occupational Safety and Health Administration's (OSHA) Hazard Communication Standard (HCS). Under HCS, OSHAregulated businesses that use materials containing 0.1% or more crystalline silica must follow Federal guidelines concerning hazard communication and worker training. Although the HCS does not require that samples be analyzed for crystalline silica, mineral suppliers or OSHAregulated

  8. Properties of paving units incorporating crushed ceramic

    Directory of Open Access Journals (Sweden)

    Dina M. Sadek

    2014-08-01

    Full Text Available The aim of this study is to investigate the effects of using crushed ceramic in the production of interlocking paving units. Eight mixes were cast. The first mix was the control mix, in which natural aggregates were used in the upper and lower layers. In the second and third mixes, coarse crushed ceramic was used in the lower layer replacing 50% and 100% of crushed stone, respectively. In the fourth and fifth mixes, fine crushed ceramic was used in the lower layer replacing 50% and 100% of natural sand, respectively. In the sixth mix, coarse and fine crushed ceramic were used in the lower layer replacing 50% of crushed stone and 50% of natural sand, respectively. Finally, in the seventh and eighth mixes, fine crushed ceramic was used in the upper layer replacing 50% and 100% of natural sand, respectively while natural sand was used in the lower layer. Tests were carried out in order to investigate the properties of the manufactured specimens after 28 days of curing. Compressive strength and abrasion resistance were determined according to the American Society for Testing and Materials (ASTM C 140 and ASTM C418, respectively. Water absorption, split tensile strength, abrasion resistance, as well as, skid resistance were determined according to both Egyptian Standard Specifications (ESS 4382 and European Standard (EN 1338. The Egyptian standard is identical with the European standard. The results indicate that it is feasible to use fine crushed ceramic in the manufacture of paving blocks.

  9. Ceramic Seal.

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-11-01

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

  10. ceramic pigment

    Indian Academy of Sciences (India)

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

  11. Light emitting ceramic device and method for fabricating the same

    Science.gov (United States)

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

    2004-11-30

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

  12. Fracture-induced amorphization of polycrystalline SiO2 stishovite: a potential platform for toughening in ceramics

    Science.gov (United States)

    Nishiyama, Norimasa; Wakai, Fumihiro; Ohfuji, Hiroaki; Tamenori, Yusuke; Murata, Hidenobu; Taniguchi, Takashi; Matsushita, Masafumi; Takahashi, Manabu; Kulik, Eleonora; Yoshida, Kimiko; Wada, Kouhei; Bednarcik, Jozef; Irifune, Tetsuo

    2014-10-01

    Silicon dioxide has eight stable crystalline phases at conditions of the Earth's rocky parts. Many metastable phases including amorphous phases have been known, which indicates the presence of large kinetic barriers. As a consequence, some crystalline silica phases transform to amorphous phases by bypassing the liquid via two different pathways. Here we show a new pathway, a fracture-induced amorphization of stishovite that is a high-pressure polymorph. The amorphization accompanies a huge volume expansion of ~100% and occurs in a thin layer whose thickness from the fracture surface is several tens of nanometers. Amorphous silica materials that look like strings or worms were observed on the fracture surfaces. The amount of amorphous silica near the fracture surfaces is positively correlated with indentation fracture toughness. This result indicates that the fracture-induced amorphization causes toughening of stishovite polycrystals. The fracture-induced solid-state amorphization may provide a potential platform for toughening in ceramics.

  13. The radiolysis of lithium oxide ceramics

    Energy Technology Data Exchange (ETDEWEB)

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

    1998-03-01

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

  14. Storing Waste in Ceramic

    Energy Technology Data Exchange (ETDEWEB)

    Bourcier, W L; Sickafus, K

    2004-07-20

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

  15. Ceramic Sintering

    Science.gov (United States)

    1974-10-01

    Plessy Co. of Frenchtown, N.J. The vendor’s analysis showed it to be 91% alpha Si^ and the rest beta . The impurity content, as determined... Cristobalite . This was also the crystalline form of the oxide on the powder on which the samples lay. Figure 5 showj oxidation data obtained at 1550oC

  16. Application of artificial neural network and adaptive neuro-fuzzy inference system to investigate corrosion rate of zirconium-based nano-ceramic layer on galvanized steel in 3.5% NaCl solution

    Energy Technology Data Exchange (ETDEWEB)

    Mousavifard, S.M. [Department of Polymer Engineering and Color Technology, Amirkabir University of Technology, Tehran (Iran, Islamic Republic of); Attar, M.M., E-mail: attar@aut.ac.ir [Department of Polymer Engineering and Color Technology, Amirkabir University of Technology, Tehran (Iran, Islamic Republic of); Ghanbari, A. [Department of Polymer Engineering and Color Technology, Amirkabir University of Technology, Tehran (Iran, Islamic Republic of); Dadgar, M. [Textile Engineering Department, Neyshabur University, Neyshabur (Iran, Islamic Republic of)

    2015-08-05

    Highlights: • Film formation of Zr-based conversion coating under different conditions was investigated. • We study the effect of some parameters on anticorrosion performance of conversion coating. • Optimization of processing conditions for surface treatment of galvanized steel was obtained. • Modeling and predicting corrosion current density of treated surfaces was performed using ANN and ANFIS. - Abstract: A nano-ceramic Zr-based conversion solution was prepared and optimization of Zr concentration, pH, temperature and immersion time for the treatment of hot-dip galvanized steel (HDG) was performed. SEM microscopy was utilized to investigate the microstructure and film formation of the layer and the anticorrosion performance of conversion coating was studied using polarization test. Artificial intelligence systems (ANN and ANFIS) were applied on the data obtained from polarization test and the models for predicting corrosion current density values were attained. The outcome of these models showed proper predictability of the methods. The influence of input parameters was discussed and the optimized conditions for Zr-based conversion layer formation on the galvanized steel were obtained as follows: pH 3.8–4.5, Zr concentration of about 100 ppm, ambient temperature and immersion time of about 90 s.

  17. Triamterene crystalline nephropathy.

    Science.gov (United States)

    Nasr, Samih H; Milliner, Dawn S; Wooldridge, Thomas D; Sethi, Sanjeev

    2014-01-01

    Medications can cause a tubulointerstitial insult leading to acute kidney injury through multiple mechanisms. Acute tubular injury, a dose-dependent process, occurs due to direct toxicity on tubular cells. Acute interstitial nephritis characterized by interstitial inflammation and tubulitis develops from drugs that incite an allergic reaction. Other less common mechanisms include osmotic nephrosis and crystalline nephropathy. The latter complication is rare but has been associated with several drugs, such as sulfadiazine, indinavir, methotrexate, and ciprofloxacin. Triamterene crystalline nephropathy has been reported only rarely, and its histologic characteristics are not well characterized. We report 2 cases of triamterene crystalline nephropathy, one of which initially was misdiagnosed as 2,8-dihydroxyadenine crystalline nephropathy. Copyright © 2013 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.

  18. What Is Crystalline Silica?

    Science.gov (United States)

    ... carcinogen. Additionally, breathing crystalline silica dust can cause silicosis , which in severe cases can be disabling, or ... take in oxygen. There is no cure for silicosis. Since silicosis affects lung function, it makes one ...

  19. Nanomembrane structures having mixed crystalline orientations and compositions

    Energy Technology Data Exchange (ETDEWEB)

    Lagally, Max G.; Scott, Shelley A.; Savage, Donald E.

    2014-08-12

    The present nanomembrane structures include a multilayer film comprising a single-crystalline layer of semiconductor material disposed between two other single-crystalline layers of semiconductor material. A plurality of holes extending through the nanomembrane are at least partially, and preferably entirely, filled with a filler material which is also a semiconductor, but which differs from the nanomembrane semiconductor materials in composition, crystal orientation, or both.

  20. An Experimental Study on Mechanical Modeling of Ceramics Based on Microstructure

    Directory of Open Access Journals (Sweden)

    Ya-Nan Zhang

    2015-11-01

    Full Text Available The actual grinding result of ceramics has not been well predicted by the present mechanical models. No allowance is made for direct effects of materials microstructure and almost all the mechanical models were obtained based on crystalline ceramics. In order to improve the mechanical models of ceramics, surface grinding experiments on crystalline ceramics and non-crystalline ceramics were conducted in this research. The normal and tangential grinding forces were measured to calculate single grit force and specific grinding energy. Grinding surfaces were observed. For crystalline alumina ceramics, the predictive modeling of normal force per grit fits well with the experimental result, when the maximum undeformed chip thickness is less than a critical depth, which turns out to be close to the grain size of alumina. Meanwhile, there is a negative correlation between the specific grinding energy and the maximum undeformed chip thickness. With the decreasing maximum undeformed chip thickness, the proportions of ductile removal and transgranular fracture increase. However, the grinding force models are not applicable for non-crystalline ceramic fused silica and the specific grinding energy fluctuates irregularly as a function of maximum undeformed chip thickness seen from the experiment.

  1. Letter report on PCT/Monolith glass ceramic corrosion tests

    Energy Technology Data Exchange (ETDEWEB)

    Crawford, Charles L. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2015-09-24

    The Savannah River National Laboratory (SRNL) is collaborating with personnel from Pacific Northwest National Laboratory (PNNL) to study advanced waste form glass ceramics for immobilization of waste from Used Nuclear Fuel (UNF) separations processes. The glass ceramic waste forms take advantage of both crystalline and glassy phases where ‘troublesome’ elements (e.g., low solubility in glass or very long-lived) partition to highly durable ceramic phases with the remainder of elements residing in the glassy phase. The ceramic phases are tailored to create certain minerals or unique crystalline structures that can host the radionuclides by binding them in their specific crystalline network while not adversely impacting the residual glass network (Crum et al., 2011). Glass ceramics have been demonstrated using a scaled melter test performed in a pilot scale (1/4 scale) cold crucible induction melter (CCIM) (Crum et al., 2014; Maio et al., 2015). This report summarizes recent results from both Phase I and Phase II bench scale tests involving crucible fabrication and corrosion testing of glass ceramics using the Product Consistency Test (PCT). Preliminary results from both Phase I and Phase II bench scale tests involving statistically designed matrices have previously been reported (Crawford, 2013; Crawford, 2014).

  2. Reliability and properties of core materials for all-ceramic dental restorations

    National Research Council Canada - National Science Library

    Ban, Seiji

    2008-01-01

    ... preparation than ceramics. Sixty years later, reinforcement of the jacket crown with aluminum oxide was achieved as a result of the work of McLean and Hughes. Further materials developments were based on increasing the crystalline content, for example leucite (Empress), mica (Dicor), hydroxyapatite (Cerapearl) or mixed glass oxides (In-Ceram). Pure ...

  3. Spectroradiometric and spectrophotometric translucency of ceramic materials.

    Science.gov (United States)

    Lim, Ho-Nam; Yu, Bin; Lee, Yong-Keun

    2010-10-01

    The spectroradiometer (SR) was introduced as an alternative instrument to the spectrophotometer (SP) for measuring color in dentistry. No published studies were identified on the SR-based translucency of clinically simulated dental ceramics that closely reflect clinical conditions. Furthermore, it is unclear whether there is a correlation between SR- and SP-based translucency values. The purpose of this study was to compare the translucency parameter (TP) of core, veneer, and layered ceramics determined by an SR, and to determine the correlations in TPs measured by an SR and a reflection SP. Seven A2 shade core ceramics and corresponding A2 and A3 shade veneer ceramics were fabricated with a layered thickness of 1.5 mm. The color of core, veneer, and A2- and A3-layered ceramics was measured over white and black backgrounds by an SR with 2 measuring apertures of 2.63 and 5.25 mm in diameter, and also by an SP (n=7). TP values were calculated and the differences in SR (5.25)-based TP values of the layered ceramics were analyzed with 2-way ANOVA with the fixed factors of shade designation and type of ceramic core (α=.05). The influence of the brand on the TP values of core, veneer, and A2- and A3-layered ceramics was also analyzed with 1-way ANOVA. Correlation analysis and paired t test were performed for the SR- and SP-based TP values (α=.05). SR (5.25)-based TP values of layered ceramics ranged from 4.4 to 12.5, and were influenced by the type but not by the shade designation. SR-based TP values of core, veneer, and A2- and A3-layered ceramics were influenced by the brand. SR- and SP-based TP values were highly correlated (r=0.982 to 0.987, Pceramic specimens. TP values measured by the SR and the SP were significantly different but highly correlated. Copyright © 2010 The Editorial Council of the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.

  4. Monolithic ceramics

    Science.gov (United States)

    Herbell, Thomas P.; Sanders, William A.

    1992-01-01

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

  5. The human crystallin gene families

    Directory of Open Access Journals (Sweden)

    Wistow Graeme

    2012-12-01

    Full Text Available Abstract Crystallins are the abundant, long-lived proteins of the eye lens. The major human crystallins belong to two different superfamilies: the small heat-shock proteins (α-crystallins and the βγ-crystallins. During evolution, other proteins have sometimes been recruited as crystallins to modify the properties of the lens. In the developing human lens, the enzyme betaine-homocysteine methyltransferase serves such a role. Evolutionary modification has also resulted in loss of expression of some human crystallin genes or of specific splice forms. Crystallin organization is essential for lens transparency and mutations; even minor changes to surface residues can cause cataract and loss of vision.

  6. Thermodynamics of Crystalline States

    CERN Document Server

    Fujimoto, Minoru

    2010-01-01

    Thermodynamics is a well-established discipline of physics for properties of matter in thermal equilibrium surroundings. Applying to crystals, however, the laws encounter undefined properties of crystal lattices, which therefore need to be determined for a clear and well-defined description of crystalline states. Thermodynamics of Crystalline States explores the roles played by order variables and dynamic lattices in crystals in a wholly new way. This book is divided into three parts. The book begins by clarifying basic concepts for stable crystals. Next, binary phase transitions are discussed to study collective motion of order variables, as described mostly as classical phenomena. In the third part, the multi-electron system is discussed theoretically, as a quantum-mechanical example, for the superconducting state in metallic crystals. Throughout the book, the role played by the lattice is emphasized and examined in-depth. Thermodynamics of Crystalline States is an introductory treatise and textbook on meso...

  7. Liquid crystalline dihydroazulene photoswitches

    DEFF Research Database (Denmark)

    Petersen, Anne Ugleholdt; Jevric, Martyn; Mandle, Richard J.

    2015-01-01

    A large selection of photochromic dihydroazulene (DHA) molecules incorporating various substituents at position 2 of the DHA core was prepared and investigated for their ability to form liquid crystalline phases. Incorporation of an octyloxy-substituted biphenyl substituent resulted in nematic...... to the DHA where the alignment is maintained. The systematic structural variation has revealed that a biaryl spacer between the DHA and the alkyl chain is needed for liquid crystallinity and that the one aromatic ring in the spacer cannot be substituted by a triazole. This work presents an important step...

  8. The precursors effects on biomimetic hydroxyapatite ceramic powders.

    Science.gov (United States)

    Yoruç, Afife Binnaz Hazar; Aydınoğlu, Aysu

    2017-06-01

    In this study, effects of the starting material on chemical, physical, and biological properties of biomimetic hydroxyapatite ceramic powders (BHA) were investigated. Characterization and chemical analysis of BHA powders were performed by using XRD, FT-IR, and ICP-AES. Microstructural features such as size and morphology of the resulting BHA powders were characterized by using BET, nano particle sizer, pycnometer, and SEM. Additionally, biological properties of the BHA ceramic powders were also investigated by using water-soluble tetrazolium salts test (WST-1). According to the chemical analysis of BHA ceramic powders, chemical structures of ceramics which are prepared under different conditions and by using different starting materials show differences. Ceramic powders which are produced at 80°C are mainly composed of hydroxyapatite, dental hydroxyapatite (contain Na and Mg elements in addition to Ca), and calcium phosphate sulfide. However, these structures are altered at high temperatures such as 900°C depending on the features of starting materials and form various calcium phosphate ceramics and/or their mixtures such as Na-Mg-hydroxyapatite, hydroxyapatite, Mg-Whitlockit, and chloroapatite. In vitro cytotoxicity studies showed that amorphous ceramics produced at 80°C and ceramics containing chloroapatite structure as main or secondary phases were found to be extremely cytotoxic. Furthermore, cell culture studies showed that highly crystalline pure hydroxyapatite structures were extremely cytotoxic due to their high crystallinity values. Consequently, the current study indicates that the selection of starting materials which can be used in the production of calcium phosphate ceramics is very important. It is possible to produce calcium phosphate ceramics which have sufficient biocompatibility at physiological pH values and by using appropriate starting materials. Copyright © 2017 Elsevier B.V. All rights reserved.

  9. Contact method to allow benign failure in ceramic capacitor having self-clearing feature

    Science.gov (United States)

    Myers, John D; Taylor, Ralph S

    2012-06-26

    A capacitor exhibiting a benign failure mode has a first electrode layer, a first ceramic dielectric layer deposited on a surface of the first electrode, and a second electrode layer disposed on the ceramic dielectric layer, wherein selected areas of the ceramic dielectric layer have additional dielectric material of sufficient thickness to exhibit a higher dielectric breakdown voltage than the remaining majority of the dielectric layer. The added thickness of the dielectric layer in selected areas allows lead connections to be made at the selected areas of greater dielectric thickness while substantially eliminating a risk of dielectric breakdown and failure at the lead connections, whereby the benign failure mode is preserved.

  10. Method for fabrication of ceramic dielectric films on copper foils

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Beihai; Narayanan, Manoj; Dorris, Stephen E.; Balachandran, Uthamalingam

    2017-06-14

    The present invention provides copper substrate coated with a lead-lanthanum-zirconium-titanium (PLZT) ceramic film, which is prepared by a method comprising applying a layer of a sol-gel composition onto a copper foil. The sol-gel composition comprises a precursor of a ceramic material suspended in 2-methoxyethanol. The layer of sol-gel is then dried at a temperature up to about 250.degree. C. The dried layer is then pyrolyzed at a temperature in the range of about 300 to about 450.degree. C. to form a ceramic film from the ceramic precursor. The ceramic film is then crystallized at a temperature in the range of about 600 to about 750.degree. C. The drying, pyrolyzing and crystallizing are performed under a flowing stream of an inert gas.

  11. Multiscale Modeling of Non-crystalline Ceramics (Glass)

    Science.gov (United States)

    2013-03-01

    theory, MD, Monte Carlo methods, or master equation techniques) this archetypal material to predict of elastic properties, diffusivity, surface...connected networks (1) a Monte -Carlo bond switching model (72- and 114-atom models) and (2) MD simulated annealing of melted silica. The ring statistics...INFORMATION CTR DTIC OCA 8725 JOHN J KINGMAN RD STE 0944 FORT BELVOIR VA 22060-6218 1 DIRECTOR US ARMY RESEARCH LAB IMAL HRA 2800 POWDER MILL RD ADELPHI

  12. POLYAMIDE WITH REDUCED CRYSTALLINITY

    NARCIS (Netherlands)

    HARINGS, JULES; DESHMUKH, YOGESH SHESHRAO; VINKEN, ESTHER; RASTOGI, SANJAY

    2009-01-01

    The invention relates to a novel process for making compositions comprising a polyamid, water and a salt, having reduced crystallinity, wherein the process comprising the steps of: a. mixing the polyamide, water and a salt b. heating the mixture to a temperature above 100°C in a range between 120°C

  13. Artificial crystalline lens

    NARCIS (Netherlands)

    Norrby, S.; Koopmans, S.; Terwee, T.

    2006-01-01

    Replacement of the crystalline lens with a synthetic soft material (ACL) has been shown to produce 3 to 5 D of accommodation following pharmacologic stimulation in primates for up to 1 year postoperatively. The eyes were relatively clear, suggesting that an injectable synthetic lens is a feasible

  14. Ceramic fiber reinforced filter

    Science.gov (United States)

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

    1991-01-01

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

  15. Fracture of ceramic/ceramic/polymer trilayers for biomechanical applications.

    Science.gov (United States)

    Deng, Yan; Miranda, Pedro; Pajares, Antonia; Guiberteau, Fernando; Lawn, Brian R

    2003-12-01

    Fracture damage in trilayers consisting of outer and inner brittle layers bonded to a compliant (polycarbonate) substrate and subjected to concentrated surface loading is analyzed. The principal mode of fracture is radial cracking at the undersurface of the inner (core) layer, even in the strongest of core ceramics--other damage modes, including radial cracking in the outer (veneer) layer, are less invasive in these all-brittle coating systems. Tests on simple trilayer structures fabricated from glasses, sapphire, and dental ceramics are used to examine the dependence of the critical load for radial fracture in terms of relative outer/inner layer thickness and modulus, and inner layer strength. An explicit relation for the critical load, based on a flexing plate model in which the outer/inner bilayer is reduced to an "equivalent" monolithic coating with "effective" composite modulus, is used to examine these dependencies. The theoretical relation describes all the major trends in the critical load data over a broad range of variables, thus providing a sound basis for trilayer design. Relevance of the analysis to dental crowns and other biomechanical applications is a central theme of the study. Copyright 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 828-833, 2003

  16. Phase evolution in zirconolite glass-ceramic wasteforms

    Science.gov (United States)

    Maddrell, Ewan R.; Paterson, Hannah C.; May, Sarah E.; Burns, Kerry M.

    2017-09-01

    The evolution of crystalline phases in a model glass-ceramic wasteform system has been studied as a function of temperature and time. The work has shown that perovskite and sphene form as transient phases before final formation of zirconolite. The study also suggests some evidence for subtle structural transformations within the zirconolite phase.

  17. Production and Characterization of Glass-Ceramic Materials for Potential Use in Dental Applications: Thermal and Mechanical Properties, Microstructure, and In Vitro Bioactivity

    Directory of Open Access Journals (Sweden)

    Francesco Baino

    2017-12-01

    Full Text Available Multicomponent silicate glasses and their corresponding glass-ceramic derivatives were prepared and tested for potential applications in dentistry. The glasses were produced via a melting-quenching process, ground and sieved to obtain fine-grained powders that were pressed in the form of small cylinders and thermally treated to obtain sintered glass-ceramic samples. X-ray diffraction investigations were carried out on the materials before and after sintering to detect the presence of crystalline phases. Thermal analyses, mechanical characterizations (assessment of bending strength, Young’s modulus, Vickers hardness, fracture toughness, and in vitro bioactivity tests in simulated body fluid were performed. On the basis of the acquired results, different potential applications in the dental field were discussed for the proposed glass-ceramics. The use of such materials can be suggested for either restorative dentistry or dental implantology, mainly depending on their peculiar bioactive and mechanical properties. At the end of the work, the feasibility of a novel full-ceramic bilayered implant was explored and discussed. This implant, comprising a highly bioactive layer expected to promote osteointegration and another one mimicking the features of tooth enamel, can have an interesting potential for whole tooth substitution.

  18. Thermodynamics of Crystalline States

    CERN Document Server

    Fujimoto, Minoru

    2013-01-01

    Thermodynamics is a well-established discipline of physics for properties of matter in thermal equilibrium with the surroundings. Applying to crystals, however, the laws encounter undefined properties of crystal lattice, which therefore need to be determined for a clear and well-defined description of crystalline states. Thermodynamics of Crystalline States explores the roles played by order variables and dynamic lattices in crystals in a wholly new way. The book begins by clarifying basic concepts for stable crystals. Next, binary phase transitions are discussed to study collective motion of order variables, as described mostly as classical phenomena. New to this edition is the examination of magnetic crystals, where magnetic symmetry is essential for magnetic phase transitions. The multi-electron system is also discussed  theoretically, as a quantum-mechanical example, for superconductivity in metallic crystals. Throughout the book, the role played by the lattice is emphasized and studied in-depth. Thermod...

  19. Liquid Crystalline Polymers

    Science.gov (United States)

    1990-02-28

    Kunststoffe (German Plastics) 78(5):411-419. Calundann, G., M. Jaffe, R. S. Jones, and H. Yoon. 1988. Fibre Reinforcements for Composite Materials, A... Kunststoffe - German Plastics 77(10):1032-1035. 47 Williams, D. J. 1987. P. 405 in Nonlinear Optical Properties of Organic Molecules and Crystals, Vol. 1...crystalline acrylate. Makromol. Chem.-Macromol. Chem. Phys. 189(l):185-194. Browstow, W. 1988. Kunststoffe (German Plastics) 78:411. Clark, N. A. and

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-02-15

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

  1. Uveitic crystalline maculopathy.

    Science.gov (United States)

    Or, Chris; Kirker, Andrew W; Forooghian, Farzin

    2015-01-01

    The purpose of this case report is to present a novel cause of crystalline maculopathy. A 52-year-old Japanese female presented with a 4-month history of decreased vision in the left eye. Best corrected visual acuity in the left eye was 20/40. Dilated fundus examination of the right eye was unremarkable, but that of the left eye demonstrated foveal yellow-green intraretinal crystals and mild vitritis. Optical coherence tomography of the left eye revealed small intraretinal fluid cysts and intraretinal crystals. Ultra-widefield fluorescein angiography was normal in the right eye, but that of the left eye demonstrated features of intermediate uveitis. There was no history or findings to suggest any cause for the crystals other than the uveitis. We propose that this may represent a novel category of crystalline retinopathy, termed uveitic crystalline maculopathy. We hypothesize that breakdown of the blood-retinal barrier as seen in uveitis may contribute to the deposition of crystals in the macula, although the precise composition of the crystals is unknown.

  2. West African crystalline maculopathy.

    Science.gov (United States)

    Browning, David J

    2004-05-01

    To report new observations in West African crystalline maculopathy. Retrospective, observational case series. Three patients drawn from a private retina practice. Review of clinical charts and photographic studies. Distribution of intraretinal crystals and changes after laser photocoagulation, and history of ingesting foods typical in a West African diet but atypical for an American diet. All patients were older than 50 years, had diabetic retinopathy, ate green vegetables not found in American diets, and showed no deleterious effects of the crystals. Kola nut ingestion in 2 patients was remote and sparse, and was unknown in a third patient. The first 2 affected patients originating outside the Ibo tribe of Nigeria are reported. The pattern of retinal crystals can be changed, and the quantity of crystals reduced, by laser photocoagulation of associated diabetic retinopathy. West African crystalline retinopathy is distinguishable from other causes of crystalline retinopathy. It may reflect a component of the West African diet, seems to have diabetic retinopathy as a promoting factor via breakdown of the blood-retina barrier, and can be modified by laser photocoagulation of diabetic retinopathy. Increased awareness of the condition will allow physicians seeing West African immigrants to make the diagnosis and treat the patients appropriately.

  3. A pseudo-single-crystalline germanium film for flexible electronics

    Energy Technology Data Exchange (ETDEWEB)

    Higashi, H.; Yamada, S.; Kanashima, T.; Hamaya, K., E-mail: hamaya@ee.es.osaka-u.ac.jp [Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531 (Japan); Kasahara, K.; Park, J.-H.; Miyao, M. [Department of Electronics, Kyushu University, 744 Motooka, Fukuoka 819-0395 (Japan); Kudo, K.; Okamoto, H.; Moto, K.; Tsunoda, I. [Kumamoto National College of Technology, 2659-2 Suya, Koshi, Kumamoto 861-1102 (Japan)

    2015-01-26

    We demonstrate large-area (∼600 μm), (111)-oriented, and high-crystallinity, i.e., pseudo-single-crystalline, germanium (Ge) films at 275 °C, where the temperature is lower than the softening temperature of a flexible substrate. A modulated gold-induced layer exchange crystallization method with an atomic-layer deposited Al{sub 2}O{sub 3} barrier and amorphous-Ge/Au multilayers is established. From the Raman measurements, we can judge that the crystallinity of the obtained Ge films is higher than those grown by aluminum-induced-crystallization methods. Even on a flexible substrate, the pseudo-single-crystalline Ge films for the circuit with thin-film transistor arrays can be achieved, leading to high-performance flexible electronics based on an inorganic-semiconductor channel.

  4. The In Vitro Bioactivity, Degradation, and Cytotoxicity of Polymer-Derived Wollastonite-Diopside Glass-Ceramics

    Science.gov (United States)

    Juraski, Amanda De Castro; Dorion Rodas, Andrea Cecilia; Elsayed, Hamada; Bernardo, Enrico; Oliveira Soares, Viviane; Daguano, Juliana

    2017-01-01

    Ca-Mg silicates are receiving a growing interest in the field of bioceramics. In a previous study, wollastonite-diopside (WD) glass-ceramics were successfully prepared by a new processing route, consisting of the heat treatment of a silicone resin embedding reactive oxide particles and a Ca/Mg-rich glass. The in vitro degradation, bioactivity, and cell response of these new WD glass-ceramics, fired at 900–1100 °C for 1 h, as a function of the Ca/Mg-rich glass content, are the aim of this investigation The results showed that WD glass-ceramics from formulations comprising different glass contents (70–100% at 900 °C, 30% at 1100 °C) exhibit the formation of an apatite-like layer on their surface after immersion in SBF for seven days, thus confirming their surface bioactivity. The XRD results showed that these samples crystallized, mainly forming wollastonite (CaSiO3) and diopside (CaMgSi2O6), but combeite (Na2Ca2Si3O9) crystalline phase was also detected. Besides in vitro bioactivity, cytotoxicity and osteoblast adhesion and proliferation tests were applied after all characterizations, and the formulation comprising 70% glass was demonstrated to be promising for further in vivo studies. PMID:28772783

  5. Cold Spray Coating of Submicronic Ceramic Particles on Poly(vinyl alcohol) in Dry and Hydrogel States

    Science.gov (United States)

    Moreau, David; Borit, François; Corté, Laurent; Guipont, Vincent

    2017-06-01

    We report an approach using cold spray technology to coat poly(vinyl alcohol) (PVA) in polymer and hydrogel states with hydroxyapatite (HA). Using porous aggregated HA powder, we hypothesized that fragmentation of the powder upon cold spray could lead to formation of a ceramic coating on the surface of the PVA substrate. However, direct spraying of this powder led to complete destruction of the swollen PVA hydrogel substrate. As an alternative, HA coatings were successfully produced by spraying onto dry PVA substrates prior to swelling in water. Dense homogeneous HA coatings composed of submicron particles were obtained using rather low-energy spraying parameters (temperature 200-250 °C, pressure 1-3 MPa). Coated PVA substrates could swell in water without removal of the ceramic layer to form HA-coated hydrogels. Microscopic observations and in situ measurements were used to explain how local heating and impact of sprayed aggregates induced surface roughening and strong binding of HA particles to the molten PVA substrate. Such an approach could lead to design of ceramic coatings whose roughness and crystallinity can be finely adjusted to improve interfacing with biological tissues.

  6. Biological evaluation of an apatite-mullite glass-ceramic produced via selective laser sintering.

    Science.gov (United States)

    Goodridge, Ruth D; Wood, David J; Ohtsuki, Chikara; Dalgarno, Kenneth W

    2007-03-01

    The biological performance of a porous apatite-mullite glass-ceramic, manufactured via a selective laser sintering (SLS) method, was evaluated to determine its potential as a bone replacement material. Direct contact and extract assays were used to assess the cytotoxicity of the material. A pilot animal study, implanting the material into rabbit tibiae for 4 weeks, was also carried out to assess in vivo bioactivity. The material produced by SLS did not show any acute cytotoxic effects by either contact or extract methods. There was no evidence of an apatite layer forming on the surface of the material when soaked in SBF for 30 days, suggesting that the material was unlikely to exhibit bioactive behaviour in vivo. It is hypothesized that the material was unable to form an apatite layer in SBF due to the fact that this glass-ceramic was highly crystalline and the fluorapatite crystal phase was relatively stable in SBF, as were the two aluminosilicate crystal phases. There was thus no release of calcium and phosphorus and no formation of silanol groups to trigger apatite deposition from solution within the test time period. Following implantation in rabbit tibiae for 4 weeks, bone was seen to have grown into the porous structure of the laser-sintered parts, and appeared to be very close to, or directly contacting, the material surface. This result may reflect the local environment in vivo compared to that artificially found with the in vitro SBF test and, furthermore, confirms previous in vivo data on these glass-ceramics.

  7. Verification of ceramic structures

    NARCIS (Netherlands)

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

    2012-01-01

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

  8. Ceramic Laser Materials

    Directory of Open Access Journals (Sweden)

    Guillermo Villalobos

    2012-02-01

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

  9. Joining Ceramics By Brazing

    Science.gov (United States)

    Chiaramonte, Francis P.; Sudsina, Michael W.

    1992-01-01

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

  10. Evaluation of a novel multiple phase veneering ceramic.

    Science.gov (United States)

    Sinthuprasirt, Pannapa; van Noort, Richard; Moorehead, Robert; Pollington, Sarah

    2015-04-01

    To produce a new veneering ceramic based on the production of a multiple phase glass-ceramic with improved performance in terms of strength and toughness. A composition of 60% leucite, 20% diopside and 20% feldspathic glass was prepared, blended and a heat treatment schedule of 930°C for 5 min was derived from differential thermal analysis (DTA) of the glasses. X-ray diffraction (XRD) and SEM analysis determined the crystalline phases and microstructure. Chemical solubility, biaxial flexural strength (BFS), fracture toughness, hardness, total transmittance and coefficient of thermal expansion (CTE) were all measured in comparison to a commercial veneering ceramic (VITA VM9). Thermal shock resistance of the leucite-diopside and VITA VM9 veneered onto a commercial high strength zirconia (Vita In-Ceram YZ) was also assessed. Statistical analysis was undertaken using Independent Samples t-test. Weibull analysis was employed to examine the reliability of the strength data. The mean chemical solubility was 6 μg/cm(2) for both ceramics (P=1.00). The mean BFS was 109 ± 8 MPa for leucite-diopside ceramic and 79 ± 11 MPa for VITA VM9 ceramic (P=0.01). Similarly, the leucite-diopside ceramic demonstrated a significantly higher fracture toughness and hardness. The average total transmittance was 46.3% for leucite-diopside ceramic and 39.8% for VITA VM9 (P=0.01). The leucite-diopside outperformed the VITA VM9 in terms of thermal shock resistance. Significance This novel veneering ceramic exhibits significant improvements in terms of mechanical properties, yet retains a high translucency and is the most appropriate choice as a veneering ceramic for a zirconia base core material. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  11. Preparation of basalt-based glass ceramics

    Directory of Open Access Journals (Sweden)

    MIHOVIL LOGAR

    2003-06-01

    Full Text Available Local and conventional raw materials–massive basalt from the Vrelo locality on Kopaonik mountain–have been used as starting materials to test their suitability for the production of glass-ceramics. Crystallization phenomena of glasses of the fused basalt rocks were studied by X-ray phase analysis, optical microscopy and other techniques. Various heat treatments were used, and their influences, on controlling the microstructures and properties of the products were studied with the aim of developing high strength glass-ceramic materials. Diopside CaMg(SiO32 and hypersthene ((Mg,FeSiO3 were identifies as the crystalline phases. The final products contained considerable amounts of a glassy phase. The crystalline size was in range of 8–480 mm with plate or needle shape. Microhardness, crashing strength and wears resistence of the glass-ceramics ranged from 6.5–7.5, from 2000–6300 kg/cm2 and from 0.1–0.2 g/cm, respectively.

  12. Crystallization and properties of a spodumene-willemite glass ceramic

    Energy Technology Data Exchange (ETDEWEB)

    Hu, A.M. [State Key Laboratory of the Metal Matrix Composites, Shanghai Jiaotong University, Shanghai 200030 (China)]. E-mail: huanmin@tsinghua.org.cn; Li, M. [State Key Laboratory of the Metal Matrix Composites, Shanghai Jiaotong University, Shanghai 200030 (China); Dali, D.L. Mao [State Key Laboratory of the Metal Matrix Composites, Shanghai Jiaotong University, Shanghai 200030 (China); Liang, K.M. [Department of Materials Science and Engineering Tsinghua University, Beijing 100084 (China)

    2005-10-15

    Spodumene-willemite glass ceramics were produced by replacement of Al{sub 2}O{sub 3} in lithium aluminium silicate by ZnO. With replacement of Al{sub 2}O{sub 3} by ZnO, the batch melting temperature, glass transition temperature (T {sub g}) and crystallization temperature (T {sub p}) all decreased. The main crystalline phases precipitated were eucriptite, {beta}-spodumene and willemite (Zn{sub 2}SiO{sub 4}). All compositions of glass ceramics showed bulk crystallization. As ZnO content increased, the grain sizes and thermal expansion coefficients increased, while the flexural strength and fracture toughness of the glass-ceramics increased first, and then decreased. The mechanical properties were correlated with crystallization and morphology of glass ceramics.

  13. Long ceramic-lined pipes produced by a centrifugal-thermit process

    Energy Technology Data Exchange (ETDEWEB)

    Odawara, O. (Dept. of Electronic Chemistry, Tokyo Institute of Technology, Nagatsuta, Midori-ku, Yokohama 227 (JP))

    1990-03-01

    Longer than 3-m ceramic-lined pipes can be produced by means of a thermit-reaction-induced process under the influence of a centrifugal force (centrifugal-thermit process). By igniting only a part of the reactant, the thermit reaction rapidly proceeds to provide a ceramic lining of homogeneous quality in the direction of the pipe length. As a result of the residual stress measurement of each layer forming the present ceramic-lined pipe, it is confirmed that the intermediate metal layer produced plays an important role in balancing the stress between the ceramic and outer pipe layers.

  14. Synthesis and characterization of ceramic-supported and metal-supported membrane layers for the separation of CO{sub 2} in fossil-fuel power plants; Herstellung und Charakterisierung von keramik- und metallgestuetzten Membranschichten fuer die CO{sub 2}-Abtrennung in fossilen Kraftwerken

    Energy Technology Data Exchange (ETDEWEB)

    Hauler, Felix

    2010-07-01

    The separation of CO{sub 2} in fossil fuel power plants has become a very important issue due to the contribution of this greenhouse gas to global warming. Thin microporous membranes are promising candidates for separating CO{sub 2} from gas flow before being exhausted into the atmosphere. The membrane demands are good permeation and separation properties and high stability under operation conditions. Novel sol-gel derived materials composed of TiO{sub 2}/ZrO{sub 2} and stabilized SiO{sub 2} seem to be promising due to their good chemical stability and microporous character, especially for the separation of H{sub 2} and CO{sub 2}. Metallic substrates should be preferred as membrane support because they exhibit practical advantages combining good mechanical stability and the benefit of facilitated joining. The present thesis deals with the development of sol-gel derived microporous membrane layers on ceramic and metallic supports for the separation of CO{sub 2}. In this context, the optimized preparation of high-quality membranes with TiO{sub 2}/ZrO{sub 2} and Ni, Co, Zr, Ti doped SiO{sub 2} top layers is presented. These multilayered membranes consist of a graded pore structure to provide a smooth transition of the pore size from the support to the functional layer. Due to the good surface properties, the ceramic substrates only need one interlayer, whereas the rough metallic substrates exhibiting larger pores require a total of three interlayers to obtain an enhanced surface quality. On both types of supports, crack-free functional layers with a thickness below 100 nm were deposited by dip-coating. The unsupported and supported sol-gel materials used for the top layers were investigated in terms of structural properties by thermal analysis, sorption measurements, X-ray diffraction and electron microscopy. Gas permeation tests with He, H{sub 2}, CO{sub 2} und N{sub 2} were carried out to determine the membrane performance with regard to permeation rates and

  15. Sintering behavior of nano-ceramic coatings

    NARCIS (Netherlands)

    De Hosson, JTM; Popma, R; Hooijmans, J; Komarneni, S; Parker, JC; Hahn, H

    2000-01-01

    This paper concentrates on the densification of sol gel derived thin nano-ceramic coatings by laser radiation and by furnace treatment. Deposition of the film is done by means of spin coating of Zirconia. The sintering of the layer is observed using a number of different measuring techniques.

  16. Creep in ceramics

    CERN Document Server

    Pelleg, Joshua

    2017-01-01

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

  17. Thin film ceramic thermocouples

    Science.gov (United States)

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

    2011-01-01

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

  18. Ceramic gas turbine shroud

    Science.gov (United States)

    Shi, Jun; Green, Kevin E.

    2014-07-22

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

  19. Modelling of fluid flow in tape casting of thin ceramics: Analytical approaches and numerical investigations

    DEFF Research Database (Denmark)

    Jabbaribehnam, Mirmasoud; Hattel, Jesper Henri

    2016-01-01

    Tape casting has been used to produce thin layers of ceramics that can be used as single layers or can be stacked and laminated into multilayered structures. Many startup products such as multilayered inductors, multilayered varistors, piezoelectrics, ceramic fuel cells and lithium ion battery co...

  20. Synthesis of nucleated glass-ceramics using oil shale fly ash.

    Science.gov (United States)

    Luan, Jingde; Li, Aimin; Su, Tong; Cui, Xiaobo

    2010-01-15

    Nucleated glass-ceramics materials were produced from oil shale fly ash obtained from Huadian thermal power plant in China with the addition of analytic reagent CaO. On basis of differential thermal analysis (DTA) results, the nucleation and crystallization temperature of two parent glass samples with different alkalinity (Ak=m(CaO)/m(SiO(2)) were identified as Tn(1)=810 degrees C, Tc(1)=956 degrees C and Tn(2)=824 degrees C, Tc(2)=966 degrees C, respectively. X-ray diffraction (XRD) analysis of the produced nucleated glass-ceramics materials revealed that there was a coexistence phenomenon of multi-crystalline phase and the main crystalline phase was anorthite ([Ca,Na][AI,Si](2)Si(2)O(8)). The microstructure of the glass-ceramics materials was examined by scanning electron microscope (SEM). SEM observation indicated that there was an increase in the quantity of sphere-shaped crystals when crystallization time increased. Furthermore, the increase of alkalinity caused more amorphous phase occurring in glass-ceramics materials. Through the tests of physical and mechanical properties, the glass-ceramics materials with more crystalline phase and fine microstructure had high density, fine performance of resisting compression (328.92 MPa) and negligible water absorption. Through chemical resistance tests, the glass-ceramics samples showed strong corrosion resistance. Overall results indicated that it was a feasible attempt to produce nucleated glass-ceramics materials for building and decorative materials from oil shale fly ash.

  1. Joining of Cf/SiC Ceramics to Nimonic Alloys

    Science.gov (United States)

    Jiménez, C.; Mergia, K.; Moutis, N. V.; Azpiroz, X. A.; Wilhelmi, Ch.; Speliotis, Th.; Messoloras, S.

    2012-05-01

    Cf/SiC ceramic composites have been brazed to Nimonic alloys using TiCuAg filler metal. In order to improve wettability and to provide compatibility between ceramic and metal, the Cf/SiC surface was metallized through the deposition of a chromium layer. Subsequent heat treatments were carried out to develop intermediate layers of chromium carbides. Excellent wetting of both the composite ceramic and the metal from the filler metal is observed in the fabricated joints. Shear tests show that failure occurs always within the ceramic material and not at the joint. In the filler region depletion of Ti and formation of Ag and Cu rich regions are observed. At the Cf/SiC-filler interface a layered structure of the filler metallic elements is observed. Titanium interacts with the SiC matrix to form carbides and silicides.

  2. Transparent ceramic scintillators for gamma-ray spectroscopy and radiography

    Energy Technology Data Exchange (ETDEWEB)

    Cherepy, Nerine

    2010-01-01

    Transparent ceramics have become available in useful sizes for a variety of applications within the past 15 years thanks to improved understanding of sintering phenomena on the nanoscale.1,2 While traditional ceramics may comprise single or multiple crystalline and amorphous mineral phases and are typically translucent or opaque to light, modern optically transparent ceramics are fully dense monoliths of micron-scale (or smaller) crystallites, in most cases formed from pure-phase cubic crystal structures. Fabrication of transparent ceramics begins with high-purity ceramic nanopowders, which are consolidated into a ‘green body’ by pressing or casting. The green body is sintered to near-full density, and the residual porosity is removed by processing the samples in a pressure vessel with high-pressure argon gas (hot isostatic pressing). A few commercial transparent ceramics are Lumicera lenses (a barium-based oxide made by Murata Mfg.), laser gain media—Nd:YAG (neodymium-doped yttrium aluminum garnet) is available from Konoshima—and transparent armor (aluminum oxynitride and spinel are available from Surmet and other vendors). As the manufacturing processes for transparent ceramics become better understood, industrial optical uses for these transparent materials with excellent mechanical robustness are likely to expand.

  3. Computational materials science aided design of glass ceramics and crystal properties (abstract only).

    Science.gov (United States)

    Mannstadt, Wolfgang

    2008-02-13

    Today's high tech materials have in many cases highly specialized properties and designed functionalities. Materials parameters like high temperature stability, high stiffness and certain optical properties have to be optimized and in many cases an adaptation to given processes is necessary. Many materials are compounds or layered structures. Thus, surface and interface properties need to be considered as well. At the same time to some extent just a few atomic layers sometimes determine the properties of the material, as is well known in semiconductor and other thin film technologies. Therefore, a detailed understanding of the materials properties at the atomic scale becomes more and more important. In addition many high tech materials have to be of high purity or selective dopant concentrations have to be adjusted to fulfill the desired functionality. Modern materials developments successfully use computational materials science to achieve that goal. Improved software tools and continuously growing computational power allow us to predict macroscopic properties of materials on the basis of microscopic/atomic ab initio simulation approaches. At Schott, special materials, in particular glasses and glass ceramics, are produced for a variety of applications. For a glass ceramic all the above mentioned difficulties for materials development arise. The properties of a glass ceramic are determined by the interplay of crystalline phases embedded in an amorphous glass matrix. For materials development the understanding of crystal structures and their properties, surfaces and interface phenomena, and amorphous systems are necessary, likewise. Each by itself is already a challenging problem. Many crystal phases that are grown within the glass matrix do not exist as single crystals or are difficult to grow in reasonable amounts for experimental investigations. The only way to obtain the properties of these crystalline phases is through 'ab initio' simulations in the computer

  4. Science and Technology of Ceramics

    Indian Academy of Sciences (India)

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

  5. Effect of Ceramic Surface Treatments after Machine Grinding on the Biaxial Flexural Strength of Different CAD/CAM Dental Ceramics

    Directory of Open Access Journals (Sweden)

    Hossein Bagheri

    2016-05-01

    Full Text Available Objectives: This study aimed to evaluate the effect of different ceramic surface treatments after machining grinding on the biaxial flexural strength (BFS of machinable dental ceramics with different crystalline phases.Materials and Methods: Disk-shape specimens (10mm in diameter and 1.3mm in thickness of machinable ceramic cores (two silica-based and one zirconia-based ceramics were prepared. Each type of the ceramic surfaces was then randomly treated (n=15 with different treatments as follows: 1 machined finish as control, 2 machined finish and sandblasting with alumina, and 3 machined finish and hydrofluoric acid etching for the leucite and lithium disilicate-based ceramics, and for the zirconia; 1 machined finish and post-sintered as control, 2 machined finish, post-sintered, and sandblasting, and 3 machined finish, post-sintered, and Nd;YAG laser irradiation. The BFS were measured in a universal testing machine. Data based were analyzed by ANOVA and Tukey's multiple comparisons post-hoc test (α=0.05.Results: The mean BFS of machined finish only surfaces for leucite ceramic was significantly higher than that of sandblasted (P=0.001 and acid etched surfaces (P=0.005. A significantly lower BFS was found after sandblasting for lithium disilicate compared with that of other groups (P<0.05. Sandblasting significantly increased the BFS for the zirconia (P<0.05, but the BFS was significantly decreased after laser irradiation (P<0.05.    Conclusions: The BFS of the machinable ceramics was affected by the type of ceramic material and surface treatment method. Sandblasting with alumina was detrimental to the strength of only silica-based ceramics. Nd:YAG laser irradiation may lead to substantial strength degradation of zirconia. 

  6. High quality boron-doped epitaxial layers grown at 200°C from SiF4/H2/Ar gas mixtures for emitter formation in crystalline silicon solar cells

    Science.gov (United States)

    Léal, Ronan; Haddad, Farah; Poulain, Gilles; Maurice, Jean-Luc; Roca i Cabarrocas, Pere

    2017-02-01

    Controlling the doping profile in solar cells emitter and front/back surface field is mandatory to reach high efficiencies. In the current state of the art, these doped layers are made by dopant diffusion at around 900°C, which implies potential temperature induced damages in the c-Si absorber and for which a precise control of doping is difficult. An alternative solution based on boron-doped epitaxial silicon layers grown by plasma-enhanced chemical vapor deposition (PECVD) from 200°C using SiF4/H2/Ar/B2H6 chemistry is reported. The structural properties of the doped and undoped epitaxial layers were assessed by spectroscopic ellipsometry (SE), high resolution transmission electron microscopy (HR-TEM) and X-ray diffraction (XRD). The incorporation of boron has been studied via plasma profiling time of flight mass spectrometry (PP-TOFMS) and secondary ion mass spectrometry (SIMS) measurements. The boron-doped epitaxial layers revealed excellent structural and electrical properties even for high carrier concentrations (>1019cm-3). Sheet resistances between 100 and 130 Ω/sq can been obtained depending on the thickness and the doping concentration, which is within the range of targeted values for emitters in c-Si solar cells. Electrochemical capacitance voltage (ECV) revealed a uniform doping profile around 3.1019 cm-3 and by comparing with SIMS measurement a doping efficiency around 50% has been found.

  7. High quality boron-doped epitaxial layers grown at 200°C from SiF4/H2/Ar gas mixtures for emitter formation in crystalline silicon solar cells

    Directory of Open Access Journals (Sweden)

    Ronan Léal

    2017-02-01

    Full Text Available Controlling the doping profile in solar cells emitter and front/back surface field is mandatory to reach high efficiencies. In the current state of the art, these doped layers are made by dopant diffusion at around 900°C, which implies potential temperature induced damages in the c-Si absorber and for which a precise control of doping is difficult. An alternative solution based on boron-doped epitaxial silicon layers grown by plasma-enhanced chemical vapor deposition (PECVD from 200°C using SiF4/H2/Ar/B2H6 chemistry is reported. The structural properties of the doped and undoped epitaxial layers were assessed by spectroscopic ellipsometry (SE, high resolution transmission electron microscopy (HR-TEM and X-ray diffraction (XRD. The incorporation of boron has been studied via plasma profiling time of flight mass spectrometry (PP-TOFMS and secondary ion mass spectrometry (SIMS measurements. The boron-doped epitaxial layers revealed excellent structural and electrical properties even for high carrier concentrations (>1019cm-3. Sheet resistances between 100 and 130 Ω/sq can been obtained depending on the thickness and the doping concentration, which is within the range of targeted values for emitters in c-Si solar cells. Electrochemical capacitance voltage (ECV revealed a uniform doping profile around 3.1019 cm-3 and by comparing with SIMS measurement a doping efficiency around 50% has been found.

  8. Liquid crystalline order in polymers

    CERN Document Server

    Blumstein, Alexandre

    1978-01-01

    Liquid Crystalline Order in Polymers examines the topic of liquid crystalline order in systems containing rigid synthetic macromolecular chains. Each chapter of the book provides a review of one important area of the field. Chapter 1 discusses scattering in polymer systems with liquid crystalline order. It also introduces the field of liquid crystals. Chapter 2 treats the origin of liquid crystalline order in macromolecules by describing the in-depth study of conformation of such macromolecules in their unassociated state. The chapters that follow describe successively the liquid crystalli

  9. Microstructure and thermochromic properties of VOX-WOX-VOX ceramic thin films

    Science.gov (United States)

    Khamseh, S.; Araghi, H.; Ghahari, M.; Faghihi Sani, M. A.

    2016-03-01

    W-doped VO2 films have been synthesized via oxygen annealing of V-W-V (vanadium-tungsten-vanadium) multilayered films. The effects of middle layer's thickness of V-W-V multilayered film on structure and properties of VOX-WOX-VOX ceramic thin films were investigated. The as-deposited V-W-V multilayered film showed amorphous-like structure when mixed structure of VO2 (M) and VO2 (B) was formed in VOX-WOX-VOX ceramic thin films. Tungsten content of VOX-WOX-VOX ceramic thin films increased with increasing middle layer's thickness. With increasing middle layer's thickness, room temperature square resistance ( R sq) of VOX-WOX-VOX ceramic thin films increased from 65 to 86 kΩ/sq. The VOX-WOX-VOX ceramic thin film with the thinnest middle layer showed significant SMT (semiconductor-metal transition) when SMT became negligible on increasing middle layer's thickness.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1994-07-01

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

  11. Tuning Eu{sup 3+} emission in europium sesquioxide films by changing the crystalline phase

    Energy Technology Data Exchange (ETDEWEB)

    Mariscal, A., E-mail: antonio.mariscal@csic.es [Laser Processing Group, Instituto de Óptica, CSIC, C/ Serrano 121, 28006 Madrid (Spain); Quesada, A. [Ceramics for Smart Systems Group, Instituto de Cerámica y Vidrio, C/ Kelsen 5, 28049 Madrid (Spain); Camps, I. [Laser Processing Group, Instituto de Óptica, CSIC, C/ Serrano 121, 28006 Madrid (Spain); Palomares, F.J. [Instituto de Ciencia de Materiales de Madrid, C/ Sor Juana Inés de la Cruz 3, 28049 Madrid (Spain); Fernández, J.F. [Ceramics for Smart Systems Group, Instituto de Cerámica y Vidrio, C/ Kelsen 5, 28049 Madrid (Spain); Serna, R. [Laser Processing Group, Instituto de Óptica, CSIC, C/ Serrano 121, 28006 Madrid (Spain)

    2016-06-30

    Highlights: • PLD production of high quality europium sesquioxide (Eu{sub 2}O{sub 3}) films. • The deposition of Al{sub 2}O{sub 3} capping and/or buffer layers modifies the crystallization for Eu{sub 2}O{sub 3} films upon annealing. • The formation of cubic or monoclinic phases can be favored. • Eu{sup 3+} emission tuning is achieved as a consequence of crystal field effects. - Abstract: We report the growth of europium sesquioxide (Eu{sub 2}O{sub 3}) thin films by pulsed laser deposition (PLD) in vacuum at room temperature from a pure Eu{sub 2}O{sub 3} ceramic bulk target. The films were deposited in different configurations formed by adding capping and/or buffer layers of amorphous aluminum oxide (a-Al{sub 2}O{sub 3}). The optical properties, refractive index and extinction coefficient of the as deposited Eu{sub 2}O{sub 3} layers were obtained. X-ray photoelectron spectroscopy (XPS) measurements were done to assess its chemical composition. Post-deposition annealing was performed at 500 °C and 850 °C in air in order to achieve the formation of crystalline films and to accomplish photoluminescence emission. According to the analysis of X-ray diffraction (XRD) spectra, cubic and monoclinic phases were formed. It is found that the relative amount of the phases is related to the different film configurations, showing that the control over the crystallization phase can be realized by adequately designing the structures. All the films showed photoluminescence emission peaks (under excitation at 355 nm) that are attributed to the intra 4f-transitions of Eu{sup 3+} ions. The emission spectral shape depends on the crystalline phase of the Eu{sub 2}O{sub 3} layer. Specifically, changes in the hypersensitive {sup 5}D{sub 0} → {sup 7}F{sub 2} emission confirm the strong influence of the crystal field effect on the Eu{sup 3+} energy levels.

  12. Terahertz Spectroscopy of Crystalline and Non-Crystalline Solids

    DEFF Research Database (Denmark)

    Parrott, Edward P. J.; Fischer, Bernd M.; Gladden, Lynn F.

    2013-01-01

    Terahertz spectroscopy of crystalline and non-crystalline solids is probably one of the most active research fields within the terahertz community. Many potential applications, amongst which spectral recognition is probably one of the most prominent, have significantly stimulated the development...

  13. Hardness of basaltic glass-ceramics

    DEFF Research Database (Denmark)

    Jensen, Martin; Smedskjær, Morten Mattrup; Estrup, Maja

    2009-01-01

    The dependence of the hardness of basaltic glass-ceramics on their degree of crystallisation has been explored by means of differential scanning calorimetry, optical microscopy, x-ray diffraction, and Vickers indentation. Different degrees of crystallisation in the basaltic glasses were achieved...... by varying the temperature of heat treatment. The predominant crystalline phase in the glass was identified as augite. It was found that the hardness of the glass phase decreased slightly with an increase in the degree of crystallisation, while that of the augite phase drastically decreased....

  14. Conductive ceramic composition and method of preparation

    Science.gov (United States)

    Smith, J.L.; Kucera, E.H.

    1991-04-16

    A ceramic anode composition is formed of a multivalent metal oxide or oxygenate such as an alkali metal, transition metal oxygenate. The anode is prepared as a non-stoichiometric crystalline structure by reaction and conditioning in a hydrogen gas cover containing minor proportions of carbon dioxide and water vapor. The structure exhibits a single phase and substantially enhanced electrical conductivity over that of the corresponding stoichiometric structure. Unexpectedly, such oxides and oxygenates are found to be stable in the reducing anode fuel gas of a molten carbonate fuel cell. 4 figures.

  15. Mechanistic Studies of Superplasticity of Structural Ceramics

    Science.gov (United States)

    1992-02-01

    i6ZA A, B- Spodumene 1 13-Spoduritene 10 100 1000 0.) 1 10 Flow stress (MPa) Normalized flow stress, /q,% b c Fl. 26. (a) Lack of correlation between...3Y20A, 3Y40A, 3Y60A, and 3Y80A, 2k :-:’ silicon nitride/silicon carbide; 14 for h;d’,;yapatite, and 102 for - spodumene An example of the notation for...Argon, "Review-Steady- of Two P- Spodumene Glass-Ceramics," J Am Cer- State Creep of Single-Phase Crystalline Matter at am Soc, 67 [61 385-90 (1984) High

  16. Rotary Ultrasonic Machining of Poly-Crystalline Cubic Boron Nitride

    Directory of Open Access Journals (Sweden)

    Kuruc Marcel

    2014-12-01

    Full Text Available Poly-crystalline cubic boron nitride (PCBN is one of the hardest material. Generally, so hard materials could not be machined by conventional machining methods. Therefore, for this purpose, advanced machining methods have been designed. Rotary ultrasonic machining (RUM is included among them. RUM is based on abrasive removing mechanism of ultrasonic vibrating diamond particles, which are bonded on active part of rotating tool. It is suitable especially for machining hard and brittle materials (such as glass and ceramics. This contribution investigates this advanced machining method during machining of PCBN.

  17. Temperature Dependence of the Resonant Magnetoelectric Effect in Layered Heterostructures

    Directory of Open Access Journals (Sweden)

    Dmitrii A. Burdin

    2017-10-01

    Full Text Available The dependence of the resonant direct magnetoelectric effect on temperature is studied experimentally in planar composite structures. Samples of rectangular shapes with dimensions of 5 mm × 20 mm employed ferromagnetic layers of either an amorphous (metallic glass alloy or nickel with a thickness of 20–200 μm and piezoelectric layers of single crystalline langatate material or lead zirconate titanate piezoelectric ceramics with a thickness of 500 μm. The temperature of the samples was varied in a range between 120 and 390 K by blowing a gaseous nitrogen stream around them. It is shown that the effective characteristics of the magnetoelectric effect—such as the mechanical resonance frequency fr, the quality factor Q and the magnitude of the magnetoelectric coefficient αE at the resonance frequency—are contingent on temperature. The interrelations between the temperature changes of the characteristics of the magnetoelectric effect and the temperature variations of the following material parameters—Young’s modulus Y, the acoustic quality factor of individual layers, the dielectric constant ε, the piezoelectric modulus d of the piezoelectric layer as well as the piezomagnetic coefficients λ(n of the ferromagnetic layer—are established. The effect of temperature on the characteristics of the nonlinear magnetoelectric effect is observed for the first time. The results can be useful for designing magnetoelectric heterostructures with specified temperature characteristics, in particular, for the development of thermally stabilized magnetoelectric devices.

  18. NDE of ceramics and ceramic composites

    Science.gov (United States)

    Vary, Alex A.; Klima, Stanley J.

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

  19. Antibacterial ceramic for sandbox. Sunabayo kokin ceramics

    Energy Technology Data Exchange (ETDEWEB)

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

    1993-10-01

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

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

    Science.gov (United States)

    Anunmana, Chuchai; Champirat, Tharee; Jirajariyavej, Bundhit

    2014-06-01

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

  1. Ceramic laser materials

    Science.gov (United States)

    Ikesue, Akio; Aung, Yan Lin

    2008-12-01

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

  2. Analyses of fine paste ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Sabloff, J A [ed.

    1980-01-01

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

  3. Science and Technology of Ceramics

    Indian Academy of Sciences (India)

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

  4. Continuous Fiber Ceramic Composites

    Energy Technology Data Exchange (ETDEWEB)

    None

    2002-09-01

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

  5. Measuring Fracture Times Of Ceramics

    Science.gov (United States)

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

    1989-01-01

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

  6. Molecular Sensing by Nanoporous Crystalline Polymers

    Directory of Open Access Journals (Sweden)

    Vincenzo Venditto

    2009-12-01

    Full Text Available Chemical sensors are generally based on the integration of suitable sensitive layers and transducing mechanisms. Although inorganic porous materials can be effective, there is significant interest in the use of polymeric materials because of their easy fabrication process, lower costs and mechanical flexibility. However, porous polymeric absorbents are generally amorphous and hence present poor molecular selectivity and undesired changes of mechanical properties as a consequence of large analyte uptake. In this contribution the structure, properties and some possible applications of sensing polymeric films based on nanoporous crystalline phases, which exhibit all identical nanopores, will be reviewed. The main advantages of crystalline nanoporous polymeric materials with respect to their amorphous counterparts are, besides a higher selectivity, the ability to maintain their physical state as well as geometry, even after large guest uptake (up to 10–15 wt%, and the possibility to control guest diffusivity by controlling the orientation of the host polymeric crystalline phase. The final section of the review also describes the ability of suitable polymeric films to act as chirality sensors, i.e., to sense and memorize the presence of non-racemic volatile organic compounds.

  7. Fatigue strength testing of LTCC and alumina ceramics bonds

    Science.gov (United States)

    Dąbrowski, A.; Matkowski, P.; Golonka, L.

    2012-12-01

    In this paper the results of fatigue strength tests of ceramic joints are presented. These tests have been performed on the samples subjected to thermal and vibration fatigue as well as on the reference samples without any additional loads. The main goal of the investigation was to determine the strength of hybrid ceramics joints using tensile testing machine. The experiment enabled evaluation of fatigue effects in the mentioned joints. Geometry of test samples has been designed according to FEM simulations, performed in ANSYS FEM environment. Thermal stress as well as the stress induced by vibrations have been analyzed in the designed model. In the experiments two types of ceramics have been used — LTCC green tape DP951 (DuPont) and alumina ceramic tape. The samples have been prepared by joining two sintered ceramic beams made of different types of material. The bonds have been realized utilizing low temperature glass or a layer of LTCC green tape.

  8. Synthesis, deposition and crystal growth of CZTS nanoparticles onto ceramic tiles

    Directory of Open Access Journals (Sweden)

    Ivan Calvet

    2015-09-01

    Full Text Available The work presents a simple solvothermal method for CZTS nanoparticles preparation using hexadecylamine (HDA as a capping agent. The as-prepared CZTS powder was deposited as ink using Doctor Blade technique onto ceramic tile, as a substrate substituting the typical soda-lime glass. The as-prepared film was thermal treated at different temperatures in order to enhance the thin film crystallinity. CZTS crystal growth onto ceramic tile was obtained successfully for the first time.

  9. Crystalline Stratification in Semiconducting Polymer Thin Film Quantified by Grazing Incidence X-ray Scattering

    Science.gov (United States)

    Gann, Eliot; Caironi, Mario; Noh, Yong-Young; Kim, Yun-Hi; McNeill, Christopher R.

    The depth dependence of crystalline structure within thin films is critical for many technological applications, but has been impossible to measure directly using common techniques. In this work, by monitoring diffraction peak intensity and location and utilizing the highly angle-dependent waveguiding effects of X-rays near grazing incidence we quantitatively measure the thickness, roughness and orientation of stratified crystalline layers within thin films of a high-performance semiconducting polymer. In particular, this diffractive X-ray waveguiding reveals a self-organized 5-nm-thick crystalline surface layer with crystalline orientation orthogonal to the underlying 65-nm-thick layer. While demonstrated for an organic semiconductor film, this approach is applicable to any thin film material system where stratified crystalline structure and orientation can influence important interfacial processes such as charge injection and field-effect transport.

  10. Ceramic Technology Project

    Energy Technology Data Exchange (ETDEWEB)

    1992-03-01

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

  11. Vacuum ultraviolet photoabsorption spectroscopy of crystalline and amorphous benzene

    DEFF Research Database (Denmark)

    Dawes, Anita; Pascual, Natalia; Hoffmann, Soren V.

    2017-01-01

    We present the first high resolution vacuum ultraviolet photoabsorption study of amorphous benzene with com parisons to annealed crystalline benzene and the gas phase. Vapour deposited benzene layers w ere grow n at 25 K and annealed to 90 K under conditions pertinent to interstellaricy dust grains...

  12. Amorphous and crystalline silicon based heterojunction solar cells

    NARCIS (Netherlands)

    Schuttauf, J.A.|info:eu-repo/dai/nl/314118039

    2011-01-01

    In this thesis, research on amorphous and crystalline silicon heterojunction (SHJ) solar cells is described. Probably the most important feature of SHJ solar cells is a thin intrinsic amorphous silicion (a‑Si:H) layer that is deposited before depositing the doped emitter and back surface field. The

  13. New Hypothesis for SOFC Ceramic Oxygen Electrode Mechanisms

    DEFF Research Database (Denmark)

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

    2016-01-01

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

  14. Bioactive glasses and glass-ceramics.

    Science.gov (United States)

    Rawlings, R D

    1993-01-01

    Bioactive materials are designed to induce a specific biological activity; in most cases the desired biological activity is one that will give strong bonding to bone. A range of materials has been assessed as being capable of bonding to bone, but this paper is solely concerned with bioactive glasses and glass-ceramics. Firstly, the structure and processing of glasses and glass-ceramics are described, as a basic knowledge is essential for the understanding of the development and properties of the bioactive materials. The effect of composition and structure on the bioactivity is then discussed, and it will be shown that bioactivity is associated with the formation of an apatite layer on the surface of the implant. A survey of mechanical performance demonstrates that the structure and mechanical properties of glass-ceramics depend upon whether the processing involves casting or sintering and that the strength and toughness of glass-ceramics are superior to those of glasses. Attempts to further improve the mechanical performance by the use of non-monolithic components, i.e. bioactive coatings on metal substrates and glass and glass-ceramic matrix composites, are also reviewed and are shown to have varying degrees of success. Finally, some miscellaneous applications, namely bioactive bone cements and bone fillers, are briefly covered.

  15. Bioactive glass-ceramics coatings on alumina

    Energy Technology Data Exchange (ETDEWEB)

    Vitale Brovarone, C.; Verne, E.; Lupo, F. [Politecnico di Torino (Italy). Materials Science and Chemical Eng. Dept.; Moisescu, C. [Jena Univ. (Germany). Otto-Schott-Inst. fuer Glaschemie; Zanardi, L.; Bosetti, M.; Cannas, M. [Eastern Piemont Univ., Novara (Italy). Medical Science Dept.

    2001-07-01

    In this work, aiming to combine the mechanical performances of alumina with the surface properties of a bioactive material, we coated full density alumina substrates by a bioactive glass-ceramic GC. This latter was specially tailored, in term of costituents and specific quantity to have a thermal expansion coefficient close to that of alumina (8.5-9{sup *}10{sup -6}/ C) which is lower than most of the bioactive glasses and glass-ceramics already in use. In this way, we sought to avoid, as much as possible, the crack formation and propagation due to residual stresses generated by the thermal expansion coefficients mismatch. Furthermore, the high reactivity of alumina toward the glass-ceramic was carefully controlled to avoid deep compositional modification of the GC that will negatively affect its bioactivity. At this purpose, an intermediate layer of an appropriate glass G was coated prior to coat the bioactive glass-ceramic. On the materials obtained, preliminary biological tests have been done to evaluate glass-ceramic biocompatibility respect to alumina. (orig.)

  16. FOREWORD: Focus on innovation in ceramics research in East Asia Focus on innovation in ceramics research in East Asia

    Science.gov (United States)

    Kato, Akio; Hishita, Shunichi; Osada, Minoru; Haneda, Hajime

    2010-10-01

    Ceramics, as broadly defined, include all materials other than organic substances and metals, either crystalline or amorphous. They have been used by humans since early history and have contributed considerably to improving the quality of our life. In most cases, however, high-temperature treatment is necessary to prepare ceramics. This burdens the environment and there is therefore a great need for new ceramics processing methods. Recent technologically advanced ceramics are often composed of nanocrystallites, which have great potential for innovation in terms of exploring practical applications of nanomaterials and, consequently, reducing the environmental load. The ceramics industry had long flourished in Asia, particularly in East Asia, and even today, this region is leading the development of related materials. In line with these traditions, Japanese and Korean ceramics societies have been co-sponsoring seminars on ceramics since the 1980s. Having become more international in scope and context, a series of these seminars is now known as the International Japan-Korea Seminar on Ceramics. This focus issue contains eight key articles presented at the 26th International Japan-Korea Seminar on Ceramics held on 24-26 November 2010 at the Tsukuba International Congress Center. In particular, Fabbri et al review electrode materials for protonic solid-oxide fuel cells, and Kamiya et al outline the present situation and future prospects for transparent transistors, particularly those based on amorphous In-Ga-Zn-O films. Eitel et al discuss the progress in engineering high-strain lead-free piezoelectric ceramics. Kim and Kumar review a simple processing method for producing porous ceramics using polysiloxane precursors, Kamiya and Iijima focus on surface modification and characterization of nanomaterials, and Wan et al briefly review the strategy of reducing lattice thermal conductivity of thermoelectric materials and propose new materials for thermoelectric devices

  17. Electronic Conductivity of Vanadium-Tellurite Glass-Ceramics

    DEFF Research Database (Denmark)

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

    2013-01-01

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

  18. OXYGEN TRANSPORT CERAMIC MEMBRANES

    Energy Technology Data Exchange (ETDEWEB)

    Dr. Sukumar Bandopadhyay; Dr. Nagendra Nagabhushana

    2001-02-01

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

  19. A heat-generating bioactive glass-ceramic for hyperthermia.

    Science.gov (United States)

    Ohura, K; Ikenaga, M; Nakamura, T; Yamamuro, T; Ebisawa, Y; Kokubo, T; Kotoura, Y; Oka, M

    1991-01-01

    Glass plates of the chemical composition: CaO (29.0), SiO 2 (31.0), Fe 2O 3 (40.0), B 2O 3 (3.0), P 2O 5 (3.0) in weight ratio were heated to 1050 degrees C at a rate of 5 degrees C/min and then cooled to laboratory temperature. The resulting glass-ceramic containing magnetite and wollastonite crystals showed high-saturation magnetization. The bonding ability of this new glass-ceramic to bone tissue was evaluated using rabbit tibiae, and compared with glass of the same composition. This glass-ceramic formed a Ca, P-rich layer on its surface and bonded tightly with bone within 8 weeks of implantation. However, the glass did not form this Ca, P-rich layer, nor had it bonded with bone at 25 weeks. The bone-heating ability of this glass-ceramic was investigated by applying a max. 300-Oe, 100-kHz magnetic field. The granules of the glass-ceramic filled in the rabbit tibiae heated the whole surrounding bone to more than 42 degrees C and maintained this temperature for 30 min. Bioactive ceramics reinforce the mechanical strength of bone tissue. Furthermore, this heat-generating bioactive glass-ceramic can be used for hyperthermic treatment of bone tumors.

  20. Crystalline inclusions in granulocytic sarcoma.

    Science.gov (United States)

    Strauchen, James A; Gordon, Ronald E

    2002-01-01

    Two cases of granulocytic sarcoma were found to contain numerous crystalline inclusions identified on hematoxylin-eosin-stained sections as clusters of pointed needlelike crystals present in foci of necrosis or within macrophages. The crystals were negative for chloroacetate esterase and myeloperoxidase. Electron microscopy demonstrated homogeneously dense, bipyramidal structures, indistinguishable from Charcot-Leyden crystals. Granulocytic sarcomas may contain crystalline inclusions similar to Charcot-Leyden crystals; these structures should be distinguished from crystalline immunoglobulin inclusions occurring in cases of plasma cell myeloma and lymphoplasmacytic lymphoma, which may have a similar appearance.

  1. Synthesis of bioactive and machinable miserite glass-ceramics for dental implant applications.

    Science.gov (United States)

    Saadaldin, Selma A; Dixon, S Jeffrey; Costa, Daniel O; Rizkalla, Amin S

    2013-06-01

    To synthesize and characterize machinable, bioactive glass-ceramics (GCs) suitable for dental implant applications. A glass in the SiO2-Al2O3-CaO-CaF2-K2O-B2O3-La2O3 system was synthesized by wet chemical methods, followed by calcination, melting and quenching. Crystallization kinetics were determined by differential thermal analysis (DTA). GC discs were produced by cold pressing of the glass powder and sintered using schedules determined by DTA. The crystalline phases and microstructure of GC samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Dynamic Young's modulus (E), true hardness (Ho), fracture toughness (KIC) and brittleness index (BI) were evaluated. Bioactivity was studied by examining the formation of hydroxyapatite (HA) on the GC surfaces after soaking in simulated body fluid (SBF). Attachment and proliferation of MC3T3-E1 osteoblastic cells were assessed in vitro. Miserite [KCa5(Si2O7)(Si6O15)(OH)F] was the main crystalline phase of the GC with additional secondary phases. Microstructural studies revealed interlocking lath-like crystalline morphology. E, Ho, and KIC values for the GCs were 96±3 GPa, 5.27±0.26 GPa and 4.77±0.27 MPa m(0.5), respectively. The BI was found to be 1.11±0.05 μm(-0.5), indicating outstanding machinability. An HA surface layer was formed on the GC surfaces when soaked in SBF, indicating potential bioactivity. MC3T3-E1 cells exhibited attachment, spreading and proliferation on GC surfaces, demonstrating excellent biocompatibility. We present a novel approach for the synthesis of miserite GC with the physical and biological properties required for non-metallic dental implant applications. Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  2. Ceramic heat exchanger

    Science.gov (United States)

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

    1998-06-16

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

  3. Low cost silicon-on-ceramic photovoltaic solar cells

    Science.gov (United States)

    Koepke, B. G.; Heaps, J. D.; Grung, B. L.; Zook, J. D.; Sibold, J. D.; Leipold, M. H.

    1980-01-01

    A technique has been developed for coating low-cost mullite-based refractory substrates with thin layers of solar cell quality silicon. The technique involves first carbonizing one surface of the ceramic and then contacting it with molten silicon. The silicon wets the carbonized surface and, under the proper thermal conditions, solidifies as a large-grained sheet. Solar cells produced from this composite silicon-on-ceramic material have exhibited total area conversion efficiencies of ten percent.

  4. Faceted ceramic fibers, tapes or ribbons and epitaxial devices therefrom

    Science.gov (United States)

    Goyal, Amit [Knoxville, TN

    2012-07-24

    A crystalline article includes a single-crystal ceramic fiber, tape or ribbon. The fiber, tape or ribbon has at least one crystallographic facet along its length, which is generally at least one meter long. In the case of sapphire, the facets are R-plane, M-plane, C-plane or A-plane facets. Epitaxial articles, including superconducting articles, can be formed on the fiber, tape or ribbon.

  5. A novel processing of carbon nanotubes grown on molecular sieve coated porous ceramics

    Science.gov (United States)

    Mazumder, Sangram; Sarkar, Naboneeta; Park, Jung Gyu; Zhao, Wei; Kim, Sukyoung; Kim, Ik Jin

    2015-08-01

    The present study focuses on the growth of carbon nanotubes (CNTs) on Fe-containing zeolites coated porous ceramics by implementing three different and independent techniques, successively. Direct foaming-derived porous ceramics were subjected to hydrothermal reaction for on-site growth of NaA zeolites within it. The porous ceramics-zeolite composite was subjected to ion-exchange reaction to obtain the catalyst for CNT synthesis. Multi-walled CNTs (MWCNTs) were grown by catalytic chemical vapour deposition (CCVD) process using acetylene as carbon source. Microstructural, thermogravimetric and spectroscopic analyses showed distinctive differences in terms of hollow structural feature, yield and crystallinity of the MWCNTs with different reaction temperatures.

  6. Liquid-crystalline lanthanide complexes

    OpenAIRE

    Binnemans, Koen

    2000-01-01

    The paper describes the recent developments in the field of liquid-crystalline lanthanide complexes. The role of trivalent lanthanide ions as the central metal ion in metallomesogens is considered. An outlook for the future is given.

  7. Colour stability of aesthetic brackets: ceramic and plastic.

    Science.gov (United States)

    Filho, Hibernon Lopes; Maia, Lúcio Henrique; Araújo, Marcus V; Eliast, Carlos Nelson; Ruellas, Antônio Carlos O

    2013-05-01

    The colour stability of aesthetic brackets may differ according to their composition, morphology and surface property, which may consequently influence their aesthetic performance. To assess the colour stability of aesthetic brackets (ceramic and plastic) after simulating aging and staining. Twelve commercially manufactured ceramic brackets and four different plastic brackets were assessed. To determine possible colour change (change of E*(ab)) and the value of the NBS (National Bureau of Standards) unit system, spectrophotometric colour measurements for CIE L*, a* and b* were taken before and after the brackets were aged and stained. Statistical analysis was undertaken using a one-way ANOVA analysis of variance and a Tukey multiple comparison test (alpha = 0.05). The colour change between the various (ceramic and plastic) materials was not significant (p > 0.05), but still varied significantly (p Colour stability cannot be confirmed simply by knowing the type of material and crystalline composition or structure.

  8. A-site substitution effect of strontium on bismuth layered CaBi{sub 4}Ti{sub 4}O{sub 15} ceramics on electrical and piezoelectric properties

    Energy Technology Data Exchange (ETDEWEB)

    Tanwar, Amit, E-mail: amit07tanwar@gmail.com [Department of Physics and Astrophysics, University of Delhi, Delhi 110007 (India); Verma, Maya; Gupta, Vinay; Sreenivas, K. [Department of Physics and Astrophysics, University of Delhi, Delhi 110007 (India)

    2011-10-17

    Strontium substituted CaBi{sub 4}Ti{sub 4}O{sub 15} ceramics with the chemical formula Ca{sub 1-x}Sr{sub x}Bi{sub 4}Ti{sub 4}O{sub 15} (CSBT) (x = 0.0-1.0) have been prepared through conventional solid state route. The formation of single phase material with orthorhombic structure was verified from X-ray diffraction with incorporation of Sr substitution. Decrease in a-axis displacement of Bi ion in the perovskite structure in the CSBT ceramics were observed from the relative changes in soft mode (20 cm{sup -1}) in the Raman spectra, and increase in Sr incorporation shows the shift in ferroelectric to paraelectric phase transition temperature. The dielectric properties for all the CSBT ceramic compositions are studied as a function of temperature over the frequency range of 100 Hz-1 MHz. Curie's temperature was found to be function of Sr substitution and with increase in the Sr concentration the phase transition becomes sharper and phase transition temperature gets shifted towards lower temperature (790-545 deg. C). The behavior of ac conductivity as a function of frequency (100 Hz-1 MHz) at low temperature (<500 deg. C) follows the power law and attributed to hopping conduction mechanism. Sr substitution results in the increase in piezoelectric coefficients (d{sub 33}) whereas piezoelectric charge coefficient values were found comparable to that of PZT at room temperature. Relative changes in soft modes due to Sr incorporation results in high piezoelectricity in the CSBT ceramics.

  9. Crystalline silica-induced inflammation

    OpenAIRE

    2010-01-01

    M. Tech. The persistent presence of neutrophils is associated with a wide range of inflammatory diseases. Resolution of inflammation in these diseases is also associated with the ingestion of apoptotic neutrophils by macrophages. Inflammation and apoptosis of inflammatory cells are common known features observed in the lung following exposure to crystalline silica. What is not known is how well these apoptotic cells are cleared by macrophages in the presence of crystalline silica? To inves...

  10. Greek archaic ceramics manufactured in Huelva

    Directory of Open Access Journals (Sweden)

    Fernando González de Canales Cerisola

    2017-06-01

    Full Text Available In the late 1980s, a group of Greek Archaic pottery characterized by a greenish yellow paste was differentiated in the city of Huelva, Spain. The origin of these vases, unknown so far in other archaeological sites, had remained undetermined. This paper proves a production in situ based on the uniqueness of the location, the formal and decorative features of the documented types, certain anomalies in the shape of an amphora and, definitely, the analytical characterization of clays by X-Ray Powder Diffraction and Neutron Activation Analysis. The former method showed the formation, during the ceramic firing process, of crystalline phases (diopside, anorthite and gehlenite compatible with the primary composition of the clay from local deposits, rich in carbonates; while the latter, showed a close similarity between the chemical composition of both pottery and local clay materials. Of great interest is the presence of gold and silver in the ceramic clays. The same analytical determinations in two samples of other poorly delimited group of Archaic Greek pottery, characterized by orange, reddish or yellowish clay, reddish slip and low quality, point out that a part or perhaps most ceramic wares of such characteristics were also locally produced.

  11. Ceramic and glass radioactive waste forms

    Energy Technology Data Exchange (ETDEWEB)

    Readey, D.W.; Cooley, C.R. (comps.)

    1977-01-01

    This report contains 14 individual presentations and 6 group reports on the subject of glass and polycrystalline ceramic radioactive waste forms. It was the general consensus that the information available on glass as a waste form provided a good basis for planning on the use of glass as an initial waste form, that crystalline ceramic forms could also be good waste forms if much more development work were completed, and that prediction of the chemical and physical stability of the waste form far into the future would be much improved if the basic synergistic effects of low temperature, radiation and long times were better understood. Continuing development of the polycrystalline ceramic forms was recommended. It was concluded that the leach rate of radioactive species from the waste form is an important criterion for evaluating its suitability, particularly for the time period before solidified waste is permanently placed in the geologic isolation of a Federal repository. Separate abstracts were prepared for 12 of the individual papers; the remaining two were previously abstracted.

  12. Performance of heterojunction p+ microcrystalline silicon n crystalline silicon solar cells

    Science.gov (United States)

    van Cleef, M. W. M.; Rath, J. K.; Rubinelli, F. A.; van der Werf, C. H. M.; Schropp, R. E. I.; van der Weg, W. F.

    1997-12-01

    We have studied by Raman spectroscopy and electro-optical characterization the properties of thin boron doped microcrystalline silicon layers deposited by plasma enhanced chemical vapor deposition (PECVD) on crystalline silicon wafers and on amorphous silicon buffer layers. Thin 20-30 nm p+ μc-Si:H layers with a considerably large crystalline volume fraction (˜22%) and good window properties were deposited on crystalline silicon under moderate PECVD conditions. The performance of heterojunction solar cells incorporating such window layers were critically dependent on the interface quality and the type of buffer layer used. A large improvement of open circuit voltage is observed in these solar cells when a thin 2-3 nm wide band-gap buffer layer of intrinsic a-Si:H deposited at low temperature (˜100 °C) is inserted between the microcrystalline and crystalline silicon [complete solar cell configuration: Al/(n)c-Si/buffer/p+μc-Si:H/ITO/Ag)]. Detailed modeling studies showed that the wide band-gap a-Si:H buffer layer is able to prevent electron backdiffusion into the p+ μc-Si:H layer due to the discontinuity in the conduction band at the amorphous-crystalline silicon interface, thereby reducing the high recombination losses in the microcrystalline layer. At the same time, the discontinuity in the valence band is not limiting the hole exit to the front contact and does not deteriorate the solar cell performance. The defect density inside the crystalline silicon close to the amorphous-crystalline interface has a strong effect on the operation of the cell. An extra atomic hydrogen passivation treatment prior to buffer layer deposition, in order to reduce the number of these defects, did further enhance the values of Voc and fill factor, resulting in an efficiency of 12.2% for a cell without a back surface field and texturization.

  13. In vitro evaluation of shear bond strength of veneering ceramics to zirconia.

    Science.gov (United States)

    Ozkurt, Zeynep; Kazazoglu, Ender; Unal, Ahmet

    2010-03-01

    The bond strength between veneering ceramic and zirconia framework is the weakest link in the layered structure. To investigate the shear bond strength (SBS) of veneering ceramics to zirconia, four types of zirconia ceramics (Zirkonzahn, Cercon, Lava, DC-Zirkon) were selected. For each zirconia system, 30 disk specimens were layered with IPS e.max Ceram, Vita VM9, and a manufacturer-recommended veneering ceramic. SBS test was conducted, and fracture surface analysis was also performed to determine the failure modes. One-way ANOVA, two-way ANOVA, and Tukey's HSD tests were used to analyze the data. On shear bond strength between zirconia and their recommended veneering ceramics, statistically significant differences were observed among the different zirconia systems (pveneering ceramics than their recommended veneering ceramics for DC-Zirkon and Lava. For Zirkonzahn and Cercon, similar SBS values were observed for all kinds of veneering ceramics (p>0.05). In conclusion, the bonding of manufacturer-recommended veneering ceramic to the zirconia framework differed according to zirconia type.

  14. Filtração de aerossóis em altas temperaturas utilizando filtros cerâmicos de dupla camada: influência do diâmetro de partícula na eficiência de coleta Filtration of aerosols at high temperatures using a double layer ceramic filter: influence of the particle diameter in the collection efficiency

    Directory of Open Access Journals (Sweden)

    N. L de Freitas

    2004-12-01

    Full Text Available Neste trabalho foram utilizados filtros cerâmicos para filtração de aerossóis, constituídos por dupla camada, onde a primeira camada é formada por um suporte celular de elevada porosidade com diâmetro de poro controlado e a segunda formada por uma película filtrante. A camada suporte foi obtida pela técnica de replicação cerâmica de espuma poliuretânica, por meio da impregnação de uma suspensão aquosa de Al2O3. Foram utilizados suportes de 45 e 75 poros/polegada. A membrana filtrante (Al2O3 e argila foi a mesma para ambos os suportes, sendo composta por uma massa granular cerâmica de baixa porosidade. Os experimentos de filtração foram realizados em temperaturas de 25 a 700 ºC onde mediu-se a capacidade dos filtros de limpar um aerossol de partículas finas polidispersas (diâmetro mediano de 4,6 µm e calculou-se a eficiência de coleta para diâmetros de partícula entre 0,4 e 8,5 µm. Os resultados mostraram que a eficiência diminuiu com o aumento da temperatura e aumentou com o diâmetro da partícula.In this work, ceramic filters were used for aerosol filtration. The filters were constituted by two layers, where the first layer was formed by of a highly porous ceramic support with controlled pore size and the second layer constituted by a fine membrane. The ceramic support was obtained from polymeric foams utilizing a technique of alumina impregnation. The supports had 45 and 75 pores per inch (ppi. The membrane (a mixture of alumina and clay was the same for the two supports, with much smaller pore sizes. The filtration experiments were accomplished at temperatures varying from 25 to 700 ºC, where the ability of the filters for cleaning an aerosol constituted by fine particles (median diameter of 4.6 µm was measured. The collection efficiency was calculated for particle diameters between 0.4 and 8.5 µm. The results showed that the collection efficiency decreased with the increase of the temperature and increased

  15. Factors controlling crystallization of miserite glass-ceramic.

    Science.gov (United States)

    Muhammed, Fenik K; Moorehead, Robert; van Noort, Richard; Pollington, Sarah

    2015-12-01

    The purpose of this study was to investigate a range of variables affecting the synthesis of a miserite glass-ceramic (GC). Miserite glass was synthesized by the melt quench technique. The crystallization kinetics of the glass were determined using Differential Thermal Analysis (DTA). The glasses were ground with dry ball-milling and then sieved to different particle sizes prior to sintering. These particle sizes were submitted to heat treatment regimes in a high temperature furnace to form the GC. The crystal phases of the GC were analyzed by X-ray diffraction (XRD). Scanning electron microscopy (SEM) was used to examine the microstructure of the cerammed glass. XRD analysis confirmed that the predominant crystalline phase of the GC was miserite along with a minor crystalline phase of cristobalite only when the particle size is <20 μm and the heat treatment at 1000°C was carried out for 4h and slowly cooled at the furnace rate. For larger particle sizes and faster cooling rates, a pseudowollastonite crystalline phase was produced. Short sintering times produced either a pseudowollastonite or xonotolite crystalline phase. The current study has shown that particle size and heat treatment schedules are major factors in controlling the synthesis of miserite GC. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  16. The development steps towards the single-crystalline solidification of shaped components in space

    Science.gov (United States)

    Amende, W.; Harmathy, P.; Holl, S.; Preu, P.

    This paper gives a survey on the activities leading to the production of single crystalline ODS components under microgravity. The starting material is alloyed powder which is densified to a compact component. The sample is covered with a ceramic mold skin prior to being remelted and solidified with a single crystal matrix which contains finely distributed oxide particle dispersion. The proces is developped in ground tests and by means of a computer assisted simulation.

  17. Anionic Conducting Oxide Ceramics

    National Research Council Canada - National Science Library

    Dunn, Bruce

    1998-01-01

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

  18. Making Ceramic Cameras

    Science.gov (United States)

    Squibb, Matt

    2009-01-01

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

  19. Ceramic fiber filter technology

    Energy Technology Data Exchange (ETDEWEB)

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

    1996-06-01

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

  20. ION EXCHANGE IN GLASS-CERAMICS

    Directory of Open Access Journals (Sweden)

    George Halsey Beall

    2016-08-01

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

  1. Ion Exchange in Glass-Ceramics

    Science.gov (United States)

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

    2016-08-01

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

  2. Porous ceramic membranes

    OpenAIRE

    Biesheuvel, P. M.; Biesheuvel, Pieter Maarten

    2000-01-01

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

  3. The effect of multicolored machinable ceramics on the esthetics of all-ceramic crowns.

    Science.gov (United States)

    Reich, Sven; Hornberger, Helga

    2002-07-01

    Computer-aided design/computer-assisted machining systems offer the possibility of fabricating restorations from one machinable ceramic block. Whether multishaded blocks improve esthetic results and are a viable alternative to individually stained ceramics has not been fully determined. The aim of this investigation was to examine the effect of multishaded blocks on the esthetic appearance of all-ceramic CEREC crowns and compare these crowns with single-shade and stained restorations. Ten subjects were included in this study. For each subject, 6 different crowns were milled with the use of a CEREC machine. One crown was milled from each of the following machinable ceramic materials: CEREC Vitablocs Mark II in classic colors; Vitablocs Mark II in 3D-Master colors; Vitablocs Mark II in either classic or 3D-Master colors, with additional staining; Megadenta Bloxx multishaded; Mark II experimental multilayer; and an experimental multilayer leucite ceramic. Three independent examiners assessed the esthetic appearance of crowns fabricated to match each subject's anterior tooth shade. A scale of 1 to 6 was used to score the shade match and esthetic adaptation of each crown, with 1 representing excellent characteristics and 3.5 serving as the threshold for clinical acceptability. The examiners' scores were averaged, and the mean values were analyzed with the Wilcoxon signed rank test (P3D-Master blocks: 6 out of 10 restorations were scored below 3.5. Two of the layered materials (Mark II experimental and Bloxx) followed with 5 acceptable restorations out of 10. Within the limitations of this study, the results provide no evidence that multicolored machinable ceramics improve the esthetics of all-ceramic crowns.

  4. Effect of zirconia type on its bond strength with different veneer ceramics

    NARCIS (Netherlands)

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

    2008-01-01

    Purpose: The bond strength between veneer ceramic and the zirconia framework is the weakest component in the layered structure. This bond was proven to be sensitive to the surface finish of the framework material and to the type of the veneer ceramic and its method of application. New colored

  5. Titanium - ceramic restoration: How to improve the binding between titanium and ceramic

    Directory of Open Access Journals (Sweden)

    Harry Laksono

    2011-03-01

    Full Text Available Background: Titanium alloys has been used as an alternative to nickel-chromium alloys for metal-ceramic restorations because of its good biocompatibility and mechanical properties. This indicated that it was possible to design coping according to standards established for metal-ceramics. However, titanium is chemically reacting strongly with gaseous elements which causes problems when ceramics are fused to titanium. Purpose: To provide information about improving the bonding between titanium and ceramic. Review: Titanium has two crystal modifications, the close-packed hexagonal (α structure, up to 880° C, and above this temperature the bodycentered cubic (β structure. The principal problems is the extensive dissolution of oxygen resulting in thick, oxygen-rich titanium layers called α-case that harms the bonding of ceramic to titanium and the great mismatch in the coefficient of thermal expansion of conventional ultra-low fusing ceramic. Methods have been developed for fusing ceramic to titanium like processing methods, the used of ultra-low fusing titanium ceramic, bonding agent, and protocol for ceramic bonding to titanium. Conclusion: Titanium and titanium alloys, based on their physical and chemical properties suitable for titanium-ceramic restorations, but careful selection of processing methods, ceramic materials, laboratory skill and strict protocol for ceramic bonding to titanium are necessary to improve the bonding between titanium and ceramic.Latar Belakang: Logam campur titanium telah dipakai sebagai salah satu bahan alternatif untuk logam nikel-krom pada pembuatan restorasi keramik taut logam karena mempunyai biokompatibilitas dan sifat mekanik yang baik. Hal ini menunjukkan bahwa logam titanium dapat dipakai untuk pembuatan koping logam berdasarkan standar yang dipakai untuk pembuatan restorasi keramik taut logam. Meskipun, secara kimiawi logam titanium bereaksi dengan elemen-elemen gas yang menyebabkan masalah pada perlekatan

  6. Optical properties and Surface analysis of lithium incorporated Y2O3:Eu3+ ceramic phosphors

    Directory of Open Access Journals (Sweden)

    Jong-Seong Bae

    2010-09-01

    Full Text Available The influence of lithium doping concentration on the crystallization, the surface morphology, and the luminescent properties of Y1.92O3:Eu0.08 ceramic phosphors were investigated. The crystallinity, the surface morphology, and the photoluminescence (PL of ceramics depended highly on the Li-doping concentrations. The relationship between the crystalline and morphological structures and the luminescent properties was studied, and Li-doping was found to affect not only the enhanced crystallinity but also the luminescent brightness of Y1.92O3:Eu0.08 ceramics. In particular, the incorporation of Li+ ion into the Y2O3 lattice could induce remarkable increase in the PL intensity. The strongest emission intensity was observed with Y1.68Li0.24O3-δ:Eu0.08 ceramics whose brightness was increased by a factor of 6.5 in comparison with that of Y1.92O3:Eu0.08 ceramics.

  7. Ageing of low-firing prehistoric ceramics in hydrothermal conditions

    Directory of Open Access Journals (Sweden)

    Petra Zemenová

    2012-03-01

    Full Text Available Remains of a prehistoric ceramic object, a moon-shaped idol from the Bronze Age found in archaeological site Zdiby near Prague in the Czech Republic, were studied especially in terms of the firing temperature. Archaeological ceramics was usually fired at temperatures below 1000 °C. It contained unstable non-crystalline products, residua after calcination of clay components of a ceramic material. These products as metakaolinite can undergo a reverse rehydration to a structure close to kaolinite. The aim of this work was to prove whether the identified kaolinite in archaeological ceramics is a product of rehydration. The model compound containing high amount of kaolinite was prepared in order to follow its changes during calcination and hydrothermal treatment. Archaeological ceramics and the model compound were treated by hydrothermal ageing and studied by XRF, XRD and IR analyses. It was proved that the presence of kaolinite in the border-parts of the archaeological object was not a product of rehydration, but that it originated from the raw materials.

  8. Infrared Optical Properties of β-Spodumene Solid Solution Glass-Ceramic for Fiber-Optic Devices

    Science.gov (United States)

    Sakamoto, Akihiko; Yamamoto, Shigeru

    2006-09-01

    The IR optical properties of an opaque β-spodumene solid solution (s.s.) glass-ceramic for fiber-optic devices were studied in relation to its refractive indices in both crystalline and glass phases. We investigated the refractive indices of both phases on the basis of IR transmittance change due to the structural relaxation of the glass phase. The refractive indices of this β-spodumene s.s. glass-ceramic at a wavelength of 1550 nm in the crystalline and glass phases were first determined to be 1.530 and 1.495, respectively. It was found from the refractive index data that the optical scattering intensity of this glass-ceramic approximately follows the Rayleigh-Gans model. We also demonstrated that the inner diameter of an opaque glass-ceramic capillary used in optical fiber connectors can be optically measured with a sub-micrometer accuracy using an IR laser.

  9. Shading of ceramic crowns using digital tooth shade matching devices.

    Science.gov (United States)

    Baltzer, A; Kaufmann-Jinoian, V

    2005-04-01

    In the 1990s, there was great optimism due to the development of devices for measuring tooth shade. The frequently not so simple, visual determination of the shade of a tooth was to be done with the aid of a device which recognizes the shade and describes it accurately by reference to a color chart. However, the skepticism towards such devices was also great. It is known that the color effect frequently differs strongly when comparing a tooth from the shade guide with a metal ceramic crown, despite identical shade designation. Anyone who considers visual shade determination to be inadequate and places his hopes in digital shade matching devices will be disappointed. It is the shade-generating structures of the metal ceramic and frequently of the veneer layers that turn out to be too thin which, despite correct shade selection, cause a different color perception. Such problems have been reduced decisively with the development of fracture-proof hard porcelain caps (Vita In-Ceram) with optical characteristics similar to teeth. In addition, the Vita System 3D-Master tooth shade system developed in 1998 by Vita in cooperation with Dr. Hall from Australia, leads the practitioner to a better understanding of the primary tooth shade characteristics of "brightness (value)", "color intensity (chroma)" and "color (wave length of the visible light, hue)". These two innovations allow a more accurate estimate of the basic shade of a natural tooth (reference tooth) and the imitation in the laboratory of its natural, shade-generating structures. If digital shade measurement supplements the visual shade estimate, then a further improvement can be expected--especially in the recognition of the basic shade. Qualitative descriptions of subjective shade measurement of a natural tooth and of its imitation in the dental laboratory by ceramics can be found frequently in professional journals and publications. With digital tooth shade matching devices, which apart from the color code of

  10. Influence of resin cement shade on the color and translucency of ceramic veneers

    Directory of Open Access Journals (Sweden)

    Daiana Kelly Lopes HERNANDES

    Full Text Available ABSTRACT Objective This in vitro study evaluated the effect of two different shades of resin cement (RC- A1 and A3 layer on color change, translucency parameter (TP, and chroma of low (LT and high (HT translucent reinforced lithium disilicate ceramic laminates. Material and Methods One dual-cured RC (Variolink II, A1- and A3-shade, Ivoclar Vivadent was applied to 1-mm thick ceramic discs to create thin RC films (100 µm thick under the ceramics. The RC was exposed to light from a LED curing unit. Color change (ΔE of ceramic discs was measured according to CIEL*a*b* system with a standard illuminant D65 in reflectance mode in a spectrophotometer, operating in the light range of 360-740 nm, equipped with an integrating sphere. The color difference between black (B and white (W background readings was used for TP analysis, while chroma was calculated by the formula C*ab=(a*2+b*2½. ΔE of 3.3 was set as the threshold of clinically unacceptable. The results were evaluated by two-way ANOVA followed by Tukey's post hoc test. Results HT ceramics showed higher ΔE and higher TP than LT ceramics. A3-shade RC promoted higher ΔE than A1-shade cement, regardless of the ceramic translucency. No significant difference in TP was noted between ceramic discs with A1- and those with A3-shade cement. Ceramic with underlying RC showed lower TP than discs without RC. HT ceramics showed lower chroma than LT ceramics, regardless of the resin cement shade. The presence of A3-shade RC resulted in higher chroma than the presence of A1-shade RC. Conclusions Darker underlying RC layer promoted more pronounced changes in ceramic translucency, chroma, and shade of high translucent ceramic veneers. These differences may not be clinically differentiable.

  11. Influence of resin cement shade on the color and translucency of ceramic veneers.

    Science.gov (United States)

    Hernandes, Daiana Kelly Lopes; Arrais, Cesar Augusto Galvão; Lima, Erick de; Cesar, Paulo Francisco; Rodrigues, José Augusto

    2016-01-01

    This in vitro study evaluated the effect of two different shades of resin cement (RC- A1 and A3) layer on color change, translucency parameter (TP), and chroma of low (LT) and high (HT) translucent reinforced lithium disilicate ceramic laminates. One dual-cured RC (Variolink II, A1- and A3-shade, Ivoclar Vivadent) was applied to 1-mm thick ceramic discs to create thin RC films (100 µm thick) under the ceramics. The RC was exposed to light from a LED curing unit. Color change (ΔE) of ceramic discs was measured according to CIEL*a*b* system with a standard illuminant D65 in reflectance mode in a spectrophotometer, operating in the light range of 360-740 nm, equipped with an integrating sphere. The color difference between black (B) and white (W) background readings was used for TP analysis, while chroma was calculated by the formula C*ab=(a*2+b*2)½. ΔE of 3.3 was set as the threshold of clinically unacceptable. The results were evaluated by two-way ANOVA followed by Tukey's post hoc test. HT ceramics showed higher ΔE and higher TP than LT ceramics. A3-shade RC promoted higher ΔE than A1-shade cement, regardless of the ceramic translucency. No significant difference in TP was noted between ceramic discs with A1- and those with A3-shade cement. Ceramic with underlying RC showed lower TP than discs without RC. HT ceramics showed lower chroma than LT ceramics, regardless of the resin cement shade. The presence of A3-shade RC resulted in higher chroma than the presence of A1-shade RC. Darker underlying RC layer promoted more pronounced changes in ceramic translucency, chroma, and shade of high translucent ceramic veneers. These differences may not be clinically differentiable.

  12. Influence of resin cement shade on the color and translucency of ceramic veneers

    Science.gov (United States)

    HERNANDES, Daiana Kelly Lopes; ARRAIS, Cesar Augusto Galvão; de LIMA, Erick; CESAR, Paulo Francisco; RODRIGUES, José Augusto

    2016-01-01

    ABSTRACT Objective This in vitro study evaluated the effect of two different shades of resin cement (RC- A1 and A3) layer on color change, translucency parameter (TP), and chroma of low (LT) and high (HT) translucent reinforced lithium disilicate ceramic laminates. Material and Methods One dual-cured RC (Variolink II, A1- and A3-shade, Ivoclar Vivadent) was applied to 1-mm thick ceramic discs to create thin RC films (100 µm thick) under the ceramics. The RC was exposed to light from a LED curing unit. Color change (ΔE) of ceramic discs was measured according to CIEL*a*b* system with a standard illuminant D65 in reflectance mode in a spectrophotometer, operating in the light range of 360-740 nm, equipped with an integrating sphere. The color difference between black (B) and white (W) background readings was used for TP analysis, while chroma was calculated by the formula C* ab=(a*2+b*2)½. ΔE of 3.3 was set as the threshold of clinically unacceptable. The results were evaluated by two-way ANOVA followed by Tukey's post hoc test. Results HT ceramics showed higher ΔE and higher TP than LT ceramics. A3-shade RC promoted higher ΔE than A1-shade cement, regardless of the ceramic translucency. No significant difference in TP was noted between ceramic discs with A1- and those with A3-shade cement. Ceramic with underlying RC showed lower TP than discs without RC. HT ceramics showed lower chroma than LT ceramics, regardless of the resin cement shade. The presence of A3-shade RC resulted in higher chroma than the presence of A1-shade RC. Conclusions Darker underlying RC layer promoted more pronounced changes in ceramic translucency, chroma, and shade of high translucent ceramic veneers. These differences may not be clinically differentiable. PMID:27556211

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1994-07-01

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

  14. Effect of pH values on surface modification and solubility of phosphate bioglass-ceramics in the CaO-P 2O 5-Na 2O-SrO-ZnO system

    Science.gov (United States)

    Li, Xudong; Cai, Shu; Zhang, Wenjuang; Xu, Guohua; Zhou, Wei

    2009-08-01

    The bioactive glass-ceramics in the CaO-P 2O 5-Na 2O-SrO-ZnO system were synthesized by the sol-gel technique, and then chemically treated at different pH values to study the solubility and surface modification. Samples sintered at 650 °C for 4 h consisted of the crystalline phase β-Ca 2P 2O 7 and the glass matrix. After soaking in the solution at pH 1.0, the residual glass matrix on the surface appeared entirely dissolved and no new phase could be detected. Whereas at pH 3.0, web-like layer exhibiting peaks corresponding to CaP 2O 6 was formed and covered the entire surface of the sample. When conducted at pH 10.0, only part of the glass matrix was dissolved and a new phase Ca 4P 6O 19 was precipitated, forming the petaline layer. The chemical treatment can easily change the surface morphologies and phase composition of this bioactive glass-ceramics. The higher level of surface roughness resulting from the new-formed layer would improve the interface bonding and benefit for cell adhesion.

  15. Silicon-on ceramic process. Silicon sheet growth and device developmentt for the Large-Area Silicon Sheet Task of the Low-Cost Solar Array Project. Quarterly report No. 13, October 1-December 31, 1979

    Energy Technology Data Exchange (ETDEWEB)

    Chapman, P W; Zook, J D; Grung, B L; McHenry, K; Schuldt, S B

    1980-02-15

    Research on the technical and economic feasibility of producing solar-cell-quality sheet silicon by coating inexpensive ceramic substrates with a thin layer of polycrystalline silicon is reported. The coating methods to be developed are directed toward a minimum-cost process for producing solar cells with a terrestrial conversion efficiency of 11 percent or greater. By applying a graphite coating to one face of a ceramic substrate, molten silicon can be caused to wet only that graphite-coated face and produce uniform thin layers of large-grain polycrystalline silicon; thus, only a minimal quantity of silicon is consumed. A variety of ceramic materials have been dip coated with silicon. The investigation has shown that mullite substrates containing an excess of SiO/sub 2/ best match the thermal expansion coefficient of silicon and hence produce the best SOC layers. With such substrates, smooth and uniform silicon layers 25 cm/sup 2/ in area have been achieved with single-crystal grains as large as 4 mm in width and several cm in length. Crystal length is limited by the length of the substrate. The thickness of the coating and the size of the crystalline grains are controlled by the temperature of the melt and the rate at which the substrate is withdrawn from the melt. The solar-cell potential of this SOC sheet silicon is promising. To date, solar cells with areas from 1 to 10 cm/sup 2/ have been fabricated from material with an as-grown surface. Conversion efficiencies of about 10 percent with antireflection (AR) coating have been achieved. Such cells typically have open-circuit voltage and short-circuit current densities of 0.55V and 23 mA/cm/sup 2/, respectively.

  16. Investment Casting vs Replicast CS Considered in Terms of the Ceramic Mould Making and Dimensional Accuracy of Castings

    Directory of Open Access Journals (Sweden)

    Karwiński A.

    2014-03-01

    Full Text Available The article presents an analysis of the applicability of the Replicast CS process as an alternative to the investment casting process, considered in terms of the dimensional accuracy of castings. Ceramic shell moulds were based on the Ekosil binder and a wide range of ceramic materials, such as crystalline quartz, fused silica, aluminosilicates and zirconium silicate. The linear dimensions were measured with a Zeiss UMC 550 machine that allowed reducing to minimum the measurement uncertainty

  17. Understanding the edge crack phenomenon in ceramic laminates

    Directory of Open Access Journals (Sweden)

    O. Ševeček

    2015-10-01

    Full Text Available Layered ceramic materials (also referred to as “ceramic laminates” are becoming one of the most promising areas of materials technology aiming to improve the brittle behavior of bulk ceramics. The utilization of tailored compressive residual stresses acting as physical barriers to crack propagation has already succeeded in many ceramic systems. Relatively thick compressive layers located below the surface have proven very effective to enhance the fracture resistance and provide a minimum strength for the material. However, internal compressive stresses result in out-of plane stresses at the free surfaces, what can cause cracking of the compressive layer, forming the so-called edge cracks. Experimental observations have shown that edge cracking may be associated with the magnitude of the compressive stresses and with the thickness of the compressive layer. However, an understanding of the parameters related to the onset and extension of such edge cracks in the compressive layers is still lacking. In this work, a 2D parametric finite element model has been developed to predict the onset and propagation of an edge crack in ceramic laminates using a coupled stress-energy criterion. This approach states that a crack is originated when both stress and energy criteria are fulfilled simultaneously. Several designs with different residual stresses and a given thickness in the compressive layers have been computed. The results predict the existence of a lower bound, below no edge crack will be observed, and an upper bound, beyond which the onset of an edge crack would lead to the complete fracture of the layer

  18. Crystalline organomercuric acetates via organoboranes

    Energy Technology Data Exchange (ETDEWEB)

    Kunda, S.A.; Varma, R.S.; Kabalka, G.W.

    1984-01-01

    It is shown that the organomercuric acetates (OMA) can be synthesized rapidly using organomercury derivatives as intermediates. The OMAs can be readily prepared as crystalline solids. The reactions proceed with sufficient rapidity to make the synthesis useful for isotopic labelling of physiologically active compounds.

  19. TRIS buffer in simulated body fluid distorts the assessment of glass-ceramic scaffold bioactivity.

    Science.gov (United States)

    Rohanová, Dana; Boccaccini, Aldo Roberto; Yunos, Darmawati Mohamad; Horkavcová, Diana; Březovská, Iva; Helebrant, Aleš

    2011-06-01

    The paper deals with the characterisation of the bioactive phenomena of glass-ceramic scaffold derived from Bioglass® (containing 77 wt.% of crystalline phases Na(2)O·2CaO·3SiO(2) and CaO·SiO(2) and 23 wt.% of residual glass phase) using simulated body fluid (SBF) buffered with tris-(hydroxymethyl) aminomethane (TRIS). A significant effect of the TRIS buffer on glass-ceramic scaffold dissolution in SBF was detected. To better understand the influence of the buffer, the glass-ceramic scaffold was exposed to a series of in vitro tests using different media as follows: (i) a fresh liquid flow of SBF containing tris (hydroxymethyl) aminomethane; (ii) SBF solution without TRIS buffer; (iii) TRIS buffer alone; and (iv) demineralised water. The in vitro tests were provided under static and dynamic arrangements. SBF buffered with TRIS dissolved both the crystalline and residual glass phases of the scaffold and a crystalline form of hydroxyapatite (HAp) developed on the scaffold surface. In contrast, when TRIS buffer was not present in the solutions only the residual glassy phase dissolved and an amorphous calcium phosphate (Ca-P) phase formed on the scaffold surface. It was confirmed that the TRIS buffer primarily dissolved the crystalline phase of the glass-ceramic, doubled the dissolving rate of the scaffold and moreover supported the formation of crystalline HAp. This significant effect of the buffer TRIS on bioactive glass-ceramic scaffold degradation in SBF has not been demonstrated previously and should be considered when analysing the results of SBF immersion bioactivity tests of such systems. Copyright © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  20. Energetics of Si{sub x}O{sub y}C{sub z} polymer-derived ceramics prepared under varying conditions.

    Energy Technology Data Exchange (ETDEWEB)

    Morcos, R. M.; Navrotsky, A.; Varga, T.; Blum, Y.; Ahn, D.; Poli, F.; Muller, K.; Raj, R. (Materials Science Division); (Univ. of California at Davis); (SRI Int.); (Univ. of Colorado); (Univ. of Stuttgart)

    2008-09-01

    Incorporation of carbon at the molecular level can create unusual amorphous and nanostructures of Si-C-O polymer-derived ceramics by controlled pyrolysis of crosslinked polysiloxanes. These ceramics can resist crystallization to ultrahigh temperatures. In this work, we support earlier studies that the resistance to crystallization of these nanodomain networks is due to thermodynamic as well as kinetic factors. Calorimetric measurements of heats of dissolution in a molten oxide solvent show that these ceramics posses a negative enthalpy relative to their crystalline constituents (silicon carbide, cristobalite, and graphite). Si-C-O ceramics pyrolyzed at 1000 and 1450 C appear somewhat more energetically stable than those prepared at 1200 C.

  1. Cooled Ceramic Turbine Vane Project

    Data.gov (United States)

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

  2. Micro-Raman spectroscopy for the crystallinity characterization of UHMWPE hip cups run on joint simulators

    Science.gov (United States)

    Bertoluzza, A.; Fagnano, C.; Rossi, M.; Tinti, A.; Cacciari, G. L.

    2000-03-01

    In this work Raman microspectrometry was used to evaluate the crystallinity changes of hip cups made of ultra-high molecular weight polyethylene (UHMWPE). In vitro experiments were carried out using hip joint movement-wear simulators, run for five million cycles in water or bovine calf serum. The hip cups were subjected to mechanical friction with ceramic femoral heads (alumina-zirconia blend). The crystallinity of the polymer hip cups was studied as a function of inner surface position and thickness, from the stressed surface to the unstressed outer one. The Partial Least Square (PLS-l) calibration was used to correlate the Raman spectra with the crystallinity of the polymer measured with DSC calorimetry.

  3. Minimum Additive Waste Stabilization Using Vitreous Ceramics Interim Progress Report October 1994-September 1995

    Energy Technology Data Exchange (ETDEWEB)

    Feng, X; Hahn, W K; Gong, M [Pacific Northwest Lab., Richland, WA (United States); Gong, W; Wang, L; Ewing, R C [Univ. of New Mexico, Albuquerque, NM (United States). Dept. of Earth and Planetary Sciences

    1995-01-01

    Vitreous ceramic waste forms are being developed at Pacific Northwest Laboratory to complement glass waste forms in implementing the Minimum Additive Waste Stabilization (MAWS) Program to support the US Department of Energy`s environmental restoration efforts. These vitreous ceramics are composed of various metal-oxide crystalline phases embedded in a silicate-glass phase. This work extends the success of vitreous ceramic waste forms to treat wastes with both high metal and high alkali contents. Two successful approaches are discussed: developing high-durability alkali-binding crystals in a durable glassy matrix, and developing water-soluble crystals in a durable and continuous glassy matrix. Nepheline-vitreous ceramics were demonstrated for the immobilization of high-alkali wastes with alkali contents up to 21 wt%. The chemical durability of the nepheline-vitreous ceramics is better than the corresponding glasses, especially in over longer times. Vitreous ceramics with Cs{sub 2}O loading up to 35.4 wt% have been developed. Vitreous ceramic waste forms were developed from 90 and 100% Oak Ridge National Laboratory K-25 pond sludge. Heat treatment resulted in targeted crystal formation of spinels, potassium feldspar, and Ca-P phases. The K-25 pond sludge vitreous ceramics were up to 42 times more durable than high-level environmental assessments (EA) glass. The toxicity characteristics leach procedure (TCLP) concentration of LVC-6 is at least 2,000 times lower than US Environmental Protection Agency limits. Idaho Chemical Process Plant (ICPP) calcined wastes were immobilized into vitreous ceramics with calcine loading up to 88%. These ICPP-vitreous ceramics were more durable than the EA glass by factors of 5 to 30. Vitreous ceramic waste forms are being developed to complement, not to replace, glass waste forms.

  4. Mechanical properties of ceramics

    CERN Document Server

    Pelleg, Joshua

    2014-01-01

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

  5. Diffusion in ceramics

    CERN Document Server

    Pelleg, Joshua

    2016-01-01

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

  6. OXYGEN TRANSPORT CERAMIC MEMBRANES

    Energy Technology Data Exchange (ETDEWEB)

    Dr. Sukumar Bandopadhyay; Dr. Nagendra Nagabhushana

    2000-10-01

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

  7. Generic Crystalline Disposal Reference Case

    Energy Technology Data Exchange (ETDEWEB)

    Painter, Scott Leroy [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Chu, Shaoping [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Harp, Dylan Robert [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Perry, Frank Vinton [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Wang, Yifeng [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-02-20

    A generic reference case for disposal of spent nuclear fuel and high-level radioactive waste in crystalline rock is outlined. The generic cases are intended to support development of disposal system modeling capability by establishing relevant baseline conditions and parameters. Establishment of a generic reference case requires that the emplacement concept, waste inventory, waste form, waste package, backfill/buffer properties, EBS failure scenarios, host rock properties, and biosphere be specified. The focus in this report is on those elements that are unique to crystalline disposal, especially the geosphere representation. Three emplacement concepts are suggested for further analyses: a waste packages containing 4 PWR assemblies emplaced in boreholes in the floors of tunnels (KBS-3 concept), a 12-assembly waste package emplaced in tunnels, and a 32-assembly dual purpose canister emplaced in tunnels. In addition, three failure scenarios were suggested for future use: a nominal scenario involving corrosion of the waste package in the tunnel emplacement concepts, a manufacturing defect scenario applicable to the KBS-3 concept, and a disruptive glaciation scenario applicable to both emplacement concepts. The computational approaches required to analyze EBS failure and transport processes in a crystalline rock repository are similar to those of argillite/shale, with the most significant difference being that the EBS in a crystalline rock repository will likely experience highly heterogeneous flow rates, which should be represented in the model. The computational approaches required to analyze radionuclide transport in the natural system are very different because of the highly channelized nature of fracture flow. Computational workflows tailored to crystalline rock based on discrete transport pathways extracted from discrete fracture network models are recommended.

  8. Preparation of Cu2ZnSnS4 nano-crystalline powder by mechano-chemical method

    Science.gov (United States)

    Alirezazadeh, Farzaneh; Sheibani, Saeed; Rashchi, Fereshteh

    2018-01-01

    Copper zinc tin sulfide (Cu2ZnSnS4, CZTS) is one of the most promising ceramic materials as an absorber layer in solar cells due to its suitable band gap, high absorption coefficient and non-toxic and environmental friendly constituent elements. In this work, nano-crystalline CZTS powder was synthesized by mechanical milling. Elemental powders of Cu, Zn, Sn and were mixed in atomic ratio of 2:1:1:4 according to the stoichiometry of Cu2ZnSnS4 and then milled in a planetary high energy ball mill under argon atmosphere. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and diffusion reflectance spectroscopy (DRS). XRD results confirm the formation of single-phase CZTS with kesterite structure after 20 h of milling. Also, the mean crystallite size was about 35 nm. SEM results show that after 20 h of milling, the product has a relatively uniform particle size distribution. Optical properties of the product indicate that the band gap of prepared CZTS is 1.6 eV which is near to the optimum value for photovoltaic solar cells showing as a light absorber material in solar energy applications.

  9. Dendritic liquid-crystalline fullerene–ferrocene dyads

    OpenAIRE

    Campidelli, Stéphane; Pérez, Laura; Rodríguez-López Julián; Barberá, Joaquín; Langa, Fernando; Deschenaux, Robert

    2008-01-01

    First- and second-generation ferrocene-based dendrimers, fullerene and a second-generation liquid-crystalline poly(arylester) dendrimer carrying four cyanobiphenyl units were assembled to elaborate polyfunctional materials displaying mesomorphic and electronic properties. The targeted compounds gave rise to enantiotropic smectic A phases and organized into bilayer structures within the smectic layers. Cyclic voltammetry investigations revealed oxidation and reduction processes in agreement wi...

  10. An optical coherence tomography investigation of materials defects in ceramic fixed partial dental prostheses

    Science.gov (United States)

    Sinescu, Cosmin; Negrutiu, Meda; Hughes, Michael; Bradu, Adrian; Todea, Carmen; Rominu, Mihai; Laissue, Philippe L.; Podoleanu, Adrian Gh.

    2008-04-01

    Metal ceramic and integral ceramic fixed partial prostheses are mainly used in the frontal part of the dental arch because for esthetics reasons. The masticatory stress may induce fractures of the bridges. There are several factors that are associated with the stress state created in ceramic restorations, including: thickness of ceramic layers, mechanical properties of the materials, elastic modulus of the supporting substrate material, direction, magnitude and frequency of applied load, size and location of occlusal contact areas, residual stresses induced by processing or pores, restoration-cement interfacial defects and environmental defects. The fractures of these bridges lead to functional, esthetic and phonetic disturbances which finally render the prosthetic treatment inefficient. The purpose of this study is to evaluate the capability of optical coherence tomography (OCT) in detection and analysis of possible material defects in metal-ceramic and integral ceramic fixed partial dentures.

  11. Three-Point Bending Tests of Zirconia Core/Veneer Ceramics for Dental Restorations

    OpenAIRE

    Marrelli, Massimo; Maletta, Carmine; Inchingolo, Francesco; Alfano, Marco; Tatullo, Marco

    2013-01-01

    Introduction. The mechanical strength and the surface hardness of commercially available yttrium-doped zirconia were investigated. Furthermore, a comparative study of eight different ceramic veneers, to be used for the production of two-layered all-ceramic restorative systems, was carried out. Materials and Methods. Four types of zirconia specimens were analyzed, according to a standard ISO procedure (ISO 6872). Besides, two-layered zirconia-veneer specimens were prepared for three-point bend...

  12. High flow ceramic pot filters

    NARCIS (Netherlands)

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

    2017-01-01

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

  13. Translucency of Dental Ceramic, Post and Bracket

    Science.gov (United States)

    Lee, Yong-Keun

    2015-01-01

    Translucency of dental ceramics, esthetic posts and orthodontic brackets was reviewed. Translucency parameter (TP) and contrast ratio (CR) are generally used for translucency evaluation. For the evaluation of translucency, two criteria such as the translucency of human teeth (TP = 15–19, 1 mm thick) and the visual perceptibility threshold for the translucency difference (∆CR > 0.07 or ∆TP > 2) were used. In ceramics, translucency differences were in the perceptible range depending on the type of material and the thickness. However, variations caused by the difference in the required thickness for each layer by the material and also by the measurement protocols should be considered. As to the translucency of esthetic posts, a significant difference was found among the post systems. Translucency was influenced by the bracket composition and brand, and the differences by the brand were visually perceptible. PMID:28793634

  14. Verification of Ceramic Structures

    Science.gov (United States)

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

    2012-07-01

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

  15. Phosphate Ca{sub 1/4}Sr{sub 1/4}Zr{sub 2}(PO{sub 4}){sub 3} of the NaZr{sub 2}(PO{sub 4}){sub 3} structure type: Synthesis of a dense ceramic material and its radiation testing

    Energy Technology Data Exchange (ETDEWEB)

    Orlova, A.I., E-mail: albina.orlova@inbox.ru [N.I. Lobachevsky State University of Nizhny Novgorod, Gagarina Ave. 23, 603950 Nizhny Novgorod (Russian Federation); Volgutov, V.Yu.; Mikhailov, D.A.; Bykov, D.M. [N.I. Lobachevsky State University of Nizhny Novgorod, Gagarina Ave. 23, 603950 Nizhny Novgorod (Russian Federation); Skuratov, V.A. [Joint Institute for Nuclear Research, Joliot-Curie St. 6, 141980 Dubna (Russian Federation); Chuvil’deev, V.N.; Nokhrin, A.V.; Boldin, M.S.; Sakharov, N.V. [Physico-Technical Research Institute of the State University of Nizhny Novgorod, Gagarina Ave. 23, b. 3, 603950 Nizhny Novgorod (Russian Federation)

    2014-03-15

    Highlights: •High density ceramics with NZP structure were prepared by Spark Plasma Sintering. •Ceramic materials were irradiated in cyclotron by Xe ions with fluences 6 × 10{sup 10} to 1 × 10{sup 13} ions/cm{sup 2}. •The conditions of transformation from metamict to crystalline state have been found. -- Abstract: The powder of phosphate Ca{sub 1/4}Sr{sub 1/4}Zr{sub 2}(PO{sub 4}){sub 3} was synthesized by sol–gel processes in the presence of citric acid and ethylene glycol. Ceramic samples were prepared from this powder by Spark Plasma Sintering (SPS), their relative densities were found to be 99.5 ± 0.3% after the isothermal treatment at 860 °S for 3 min. Sintered disc-shaped ceramic samples (d = 10 mm, h = 4 mm) were bombarded at 300 K by 167 MeV Xe{sup 26+} ions with fluences ranging from 6 ⋅ 10{sup 10} to 1 ⋅ 10{sup 13} ions/cm{sup 2}. It was found that exposure to the highest fluence (10{sup 13} ion/cm{sup 2}) led to a complete amorphization of the irradiated layer. The observed phase transition is ascribed to the formation of amorphous latent tracks via dense electronic excitations. Postradiation heat treatment revealed that the transformation from metamict to crystalline form took place after annealing at T = 200, 300, 400, 500, 600 and 800 °S and t = 3, 13, 11, 5, 17 and 15 h, respectively.

  16. Experimental observation of crystalline particle flows in toroidal dust clouds

    Energy Technology Data Exchange (ETDEWEB)

    Wilms, Jochen, E-mail: wilms@physik.uni-kiel.de; Piel, Alexander [IEAP, Christian-Albrechts-Universität, D-24098 Kiel (Germany); Reichstein, Torben [IEAP, Christian-Albrechts-Universität, D-24098 Kiel (Germany); DME, Kiel University of Applied Sciences, Grenzstr. 3, D-24147 Kiel (Germany)

    2015-06-15

    The dust flow in a toroidal dust trap is studied experimentally. The flow is driven by the Hall component of the ion drag force in a magnetized plasma. Dust density waves are found in a torus with a large minor radius a, which allows for several wavelength, 2a>5λ, in the (mostly) radial direction of the ion flow. Beyond an intermediate state with radial sloshing oscillations, a crystalline dust flow with suppressed wave activity could be realized for 2a<2λ. The particles arrange themselves in distinct layers with hexagonal-like local order. Smooth transitions between states with different numbers of layers are found in the inhomogeneous flow.

  17. Supported microporous ceramic membranes

    Science.gov (United States)

    Webster, Elizabeth; Anderson, Marc

    1993-01-01

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

  18. Corundum ceramic materials modified with silica nanopowders: structure and mechanical properties

    Science.gov (United States)

    Kostytsyn, M. A.; Muratov, D. S.; Lysov, D. V.; Chuprunov, K. O.; Yudin, A. G.; Leybo, D. V.

    2016-01-01

    Filtering elements are often used in the metallurgy of rare earth metals. Corundum ceramic is one of the most suitable materials for this purpose. The process of formation and the properties of nanomodified ceramic materials, which are proposed as filtering materials with tunable effective porosity, are described. A silica nanopowder is used as a porosity-increasing agent. Vortex layer apparatus is used for mixing of precursor materials. The obtained results show that nanomodification with the vortex layer apparatus using 0.04 wt. % silica nanopowder as a modifying agent leads to an increase in the compression strength of corundum ceramic by the factor of 1.5.

  19. Corrosion Behavior and Microstructure Influence of Glass-Ceramic Nuclear Waste Forms

    Energy Technology Data Exchange (ETDEWEB)

    Matthew Asmussen, R. [Pacific Northwest National Laboratory, 902 Battelle Blvd, Richland, WA.; Neeway, James J. [Pacific Northwest National Laboratory, 902 Battelle Blvd, Richland, WA.; Kaspar, Tiffany C. [Pacific Northwest National Laboratory, 902 Battelle Blvd, Richland, WA.; Crum, Jarrod V. [Pacific Northwest National Laboratory, 902 Battelle Blvd, Richland, WA.

    2017-06-16

    Glass ceramic waste forms present a potentially viable technology for the long term immobilization and disposal of liquid nuclear wastes. Through control of chemistry during fabrication, such waste forms can have designed secondary crystalline phases within a borosilicate glass matrix. In this work, a glass ceramic containing powellite and oxyapatite secondary phases was tested for its corrosion properties in dilute conditions using single pass flow through testing (SPFT). Three glass ceramic samples were prepared using different cooling rates to produce samples with varying microstructure sizes. In testing at 90 °C in buffered pH 7 and pH 9 solutions, it was found that increasing pH and decreasing microstructure size (resulting from rapid cooling during fabrication) both led to a reduction in overall corrosion rate. The phases of the glass ceramic were found, using a combination of solutions analysis, SEM and AFM, to corrode preferably in the order of powellite > bulk glass matrix > oxyapatite.

  20. Production of coloured glass-ceramics from incinerator ash using thermal plasma technology.

    Science.gov (United States)

    Cheng, T W; Huang, M Z; Tzeng, C C; Cheng, K B; Ueng, T H

    2007-08-01

    Incineration is a major treatment process for municipal solid waste in Taiwan. It is estimated that over 1.5 Mt of incinerator ash are produced annually. This study proposes using thermal plasma technology to treat incinerator ash. Sintered glass-ceramics were produced using quenched vitrified slag with colouring agents added. The experimental results showed that the major crystalline phases developed in the sintered glass-ceramics were gehlenite and wollastonite, but many other secondary phases also appeared depending on the colouring agents added. The physical/mechanical properties, chemical resistance and toxicity characteristic leaching procedure of the coloured glass-ceramics were satisfactory. The glass-ceramic products obtained from incinerator ash treated with thermal plasma technology have great potential for building applications.

  1. Design of Ultra-High Temperature Ceramics for Improved Performance

    Science.gov (United States)

    2009-02-28

    University. China) 16:10 H070 The intluenee of multiple firing on wear behavior of dental veneering ceramic Q.P, (iao {CentralSouth I niversity...Microstructure and mechanical properties of freeze cast alumina/ zirconia layered composites .1 \\1 Lee (Pusan University, Korea) 203] iSHDIHi Research offiN AU

  2. Drying of a tape-cast layer: Numerical modelling of the evaporation process in a graded/layered material

    DEFF Research Database (Denmark)

    Jabbaribehnam, Mirmasoud; Jambhekar, V. A.; Hattel, Jesper Henri

    2016-01-01

    Evaporation of water from a ceramic layer is a key phenomenon in the drying process for the manufacturing of water-based tape cast ceramics. In this paper we present a coupled free-flow-porous-media model on the Representative Elementary Volume (REV) scale for coupling non-isothermal multi...

  3. Programmable high crystallinity carbon patterns

    Science.gov (United States)

    Wang, Xuewen; Wang, Hong; Gu, Yang; Fu, Wei; Zheng, Lu; Liu, Guowei; He, Yongmin; Long, Yi; Zhao, Wu; Zhang, Jie; Zhang, Ting; Liu, Zheng

    2017-06-01

    Carbon nanomaterials such as carbon nanotube and graphene are promising candidates for next-generation flexible electronics. However, the practical application of carbon electronics requires controlled fabrication of those materials with micro-patterned structures on flexible substrate at wafer-scale and low cost. Inspiring from the conventional photolithography process and pyrolysis of photoresist, herein, we demonstrate the synthesis of high-quality micro-patterned high crystallinity carbon. The method employed pre-patterned pyrolyzed photoresist as carbon precursors, in order to minimize the mobility of carbon during the high temperature growth, which results into high quality carbon patterns with a lateral resolution up to ~2 µm. The flexible carbon electronics are demonstrated by transferring the as-patterned high crystallinity carbon patterns to the flexible substrate, and showing asymmetric tensile-compressive response with high output resolution. These results will pave the way to the next-generation carbon-based flexible electronics and mechanical sensors.

  4. Improvement of the long term stability in the high temperature solid oxide fuel cell using functional layers

    Energy Technology Data Exchange (ETDEWEB)

    Brueckner, B.; Guenther, C.; Ruckdaeschel, R. [Siemens AG, Erlangen (Germany)] [and others

    1996-12-31

    In the planar Siemens design of the solid oxide fuel cell a metallic interconnector is used to seperate the ceramic single cells. A disadvantage of the metallic bipolar plate which consists of a chromium alloy is the formation of high volatile Cr-oxides and hydroxides at the surface at the cathode side. The reaction products evaporate and are reduced at the cathode/electrolyte interface to form new crystalline phases. This process gives rise to long term cell degradation. Protective coatings might be successful in preventing the chromium oxide evaporation. The required properties of the protective layers are (I) high electrical conductivity, (II) similar coefficients of thermal expansion to the bipolar plate (III), chemical compatibility to the bipolar plate and cathode material, (IV) a low diffusion coefficient of Cr and (V) chemical stability up to 1223K under oxygen atmosphere. Furthermore, during operation at 1223K an electrical contact between the metallic plate and the electrodes has to be maintained. This problem could be solved using ceramic layer between the metallic plate and the single cells.

  5. Tick-proof ceramics. Bo dani ceramics

    Energy Technology Data Exchange (ETDEWEB)

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

    1993-07-01

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

  6. Biocompatibility of crystalline opal nanoparticles

    Directory of Open Access Journals (Sweden)

    Hernández-Ortiz Marlen

    2012-10-01

    Full Text Available Abstract Background Silica nanoparticles are being developed as a host of biomedical and biotechnological applications. For this reason, there are more studies about biocompatibility of silica with amorphous and crystalline structure. Except hydrated silica (opal, despite is presents directly and indirectly in humans. Two sizes of crystalline opal nanoparticles were investigated in this work under criteria of toxicology. Methods In particular, cytotoxic and genotoxic effects caused by opal nanoparticles (80 and 120 nm were evaluated in cultured mouse cells via a set of bioassays, methylthiazolyldiphenyl-tetrazolium-bromide (MTT and 5-bromo-2′-deoxyuridine (BrdU. Results 3T3-NIH cells were incubated for 24 and 72 h in contact with nanocrystalline opal particles, not presented significant statistically difference in the results of cytotoxicity. Genotoxicity tests of crystalline opal nanoparticles were performed by the BrdU assay on the same cultured cells for 24 h incubation. The reduction of BrdU-incorporated cells indicates that nanocrystalline opal exposure did not caused unrepairable damage DNA. Conclusions There is no relationship between that particles size and MTT reduction, as well as BrdU incorporation, such that the opal particles did not induce cytotoxic effect and genotoxicity in cultured mouse cells.

  7. Excimer laser assisted chemical machining of SiC ceramic

    Science.gov (United States)

    Hibi, Yuko; Enomoto, Yuji; Kikuchi, Kaoru; Shikata, Nobuo; Ogiso, Hisato

    1995-02-01

    A highly effective method of machining ceramic has been newly developed using a krypton fluoride (KrF) excimer laser with a 248 nm wavelength. The laser was irradiated on SiC in water to form a soft hydrous oxide layer by photochemical reaction. The softened layer was then cut with a diamond tool to form a mirror surface finish. The optimum conditions were found for both high machining rate and better surface integrity of SiC.

  8. Effect of Nb doping on sintering and dielectric properties of PZT ceramics

    Directory of Open Access Journals (Sweden)

    Ali Mirzaei

    2016-09-01

    Full Text Available The extensive use of piezoelectric ceramics such as lead zirconate titanate (PZT in different applications became possible with the development of donor or acceptor dopants. Therefore, studies on the effect of dopants on the properties of PZT ceramics are highly demanded. In this study undoped and 2.4 mol% Nb-doped PZT (PZTN powders were successfully obtained by a solid-state reaction and calcination at 850 °C for 2 h. Crystallinity and phase formation of the prepared powders were studied using X-ray diffraction (XRD. In order to study morphology of powders, scanning electron microscopy (SEM was performed. The crystalline PZT and Nb-doped PZT powders were pelleted into discs and sintered at 1100, 1150 and 1200 °C, with a heating rate of 10 °C/min, and holding time of 1–6 h to find the optimum combination of temperature and time to produce high density ceramics. Microstructural characterization was conducted on the fractured ceramic surfaces using SEM. Density measurements showed that maximal density of 95% of the theoretical density was achieved after sintering of PZT and PZTN ceramics at 1200 °C for 2 h and 4 h, respectively. However, the results of dielectric measurements showed that PZTN ceramics have higher relative permittivity (εr ∼17960 with lower Curie temperature (∼358 °C relative to PZT (εr = 16000 at ∼363 °C as a result of fine PZTN structure as well as presence of vacancies. In addition, dielectric loss (at 1 kHz of PZT and PZTN ceramics with 95% theoretical density was 0.0087 and 0.02, respectively. The higher dielectric loss in PZTN was due to easier domain wall motions in PZTN ceramics.

  9. Atomistic study of structures and elastic properties of single crystalline ZnO nanotubes.

    Science.gov (United States)

    Moon, Wonha; Hwang, Hojung

    2008-06-04

    The structural stability and Young's modulus of single crystalline ZnO nanotubes are investigated using atomistic simulations. Unlike the case for conventional layered nanotubes, the energetic stability of single crystalline ZnO nanotubes is related to the wall thickness. The potential energy of ZnO nanotubes with fixed outer and inner diameters decreases with increasing wall thickness, while the nanotubes with the same wall thickness are independent of the outer and inner diameters. The transformation of single crystalline ZnO nanotubes with a double layer from wurtzite phase to graphitic phase suggests the possibility of wall-typed ZnO nanotubes. The size-dependent Young's modulus of ZnO nanotubes is also investigated. The wall thickness plays a significant role in the Young's modulus of single crystalline ZnO nanotubes, whereas the variation of outer and inner diameters slightly affects the Young's modulus of nanotubes with same wall thickness.

  10. Rare earth ion controlled crystallization of mica glass-ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Garai, Mrinmoy; Karmakar, Basudeb, E-mail: basudebk@cgcri.res.in

    2016-09-05

    In understanding the effects of rare earth ions to control the crystallization and microstructure of alkaline boroaluminosilicate system, the CeO{sub 2}, Nd{sub 2}O{sub 3}, Sm{sub 2}O{sub 3} and Gd{sub 2}O{sub 3} doped K{sub 2}O−MgO−B{sub 2}O{sub 3}−Al{sub 2}O{sub 3}−SiO{sub 2}−F glasses were synthesized by melt-quenching at 1550 °C. Higher density (2.82–3.06 g cm{sup −3}) and thermal stability (glass phase) is experiential on addition of rare earth content, which also affects in increasing the glass transition temperature (T{sub g}) and crystallization temperature (T{sub c}). Decrease of thermal expansion in glasses with rare earth ion content is maintained by the stabilization of glass matrix owing to their large cationic field strength. A significant change in the non-isothermal DSC thermogram observed at 750–1050 °C is attributed to fluorophlogopite crystallization. Opaque glass-ceramics were prepared from such glasses by single step heat-treatment at 1050 °C; and the predominant crystalline phases are identified as fluorophlogopite mica, KMg{sub 3}(AlSi{sub 3}O{sub 10})F{sub 2} by XRD and EDX analysis. The compact glass-ceramic microstructure by the agglomeration of fluorophlogopite mica crystallites (crystal size ∼ 100–500 nm, FESEM) is achieved in attendance of rare earth ion; and such microstructure controlled the variation of density, thermal expansion and microhardness value. Higher thermal expansion (11.11–14.08 × 10{sup −6}/K at 50–800 °C and 50–900 °C) of such glass-ceramics approve that these rare earth containing glasses can be useful for high temperature vacuum sealing application with metal or solid electrolyte. The increase of Vickers microhardness (5.27–5.61 GPa) in attendance of rare earth ions is attributed to the compact crystallinity of fluorophlogopite mica glass-ceramic microstructure. - Highlights: • Synthesis of rare earth oxide doped alkaline boroaluminosilicate glasses. • Development of opaque

  11. Experimental Parameter Effect on Ceramic Coating Film on LY12 Alloy by Micro-arc Oxidation

    Science.gov (United States)

    Zhao, H.; Yang, J. H.; Wang, X. H.

    2017-09-01

    Ceramic coatings were fabricated on the surface of LY12 aluminum alloy by micro-arc oxidation (MAO) method in NaSiO3-NaOH solution. Effect of experimental parameter on the MAO film was investigated. The results show that the ceramic layers formed on the surface of the alloy show different surface morphologies, and thickness of MAO film increases with the increase of voltage and oxidation time. These films contain two layers, an outer porous layer and an inner barrier layer, which consists mainly of γ-Al2O3 phase and a small amount of α-Al2O3 phase..

  12. Transformation Toughening of Ceramics

    Science.gov (United States)

    1992-03-01

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

  13. Microporous alumina ceramic membranes

    Science.gov (United States)

    Anderson, Marc A.; Sheng, Guangyao

    1993-01-01

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

  14. OXYGEN TRANSPORT CERAMIC MEMBRANES

    Energy Technology Data Exchange (ETDEWEB)

    Dr. Sukumar Bandopadhyay; Dr. Nagendfra Nagabhushana

    2001-07-01

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

  15. Bonding strength of glass-ceramic trabecular-like coatings to ceramic substrates for prosthetic applications.

    Science.gov (United States)

    Chen, Qiang; Baino, Francesco; Pugno, Nicola M; Vitale-Brovarone, Chiara

    2013-04-01

    A new approach based on the concepts of quantized fracture mechanics (QFM) is presented and discussed in this paper to estimate the bonding strength of trabecular-like coatings, i.e. glass-ceramic scaffolds mimicking the architecture of cancellous bone, to ceramic substrates. The innovative application of glass-derived scaffolds as trabecular-like coatings is proposed in order to enhance the osteointegration of prosthetic ceramic devices. The scaffolds, prepared by polymeric sponge replication, are joined to alumina substrates by a dense glass-ceramic coating (interlayer) and the so-obtained 3-layer constructs are investigated from micro-structural, morphological and mechanical viewpoints. In particular, the fracture strengths of three different crack propagation modes, i.e. glass-derived scaffold fracture, interface delamination or mixed fracture, are predicted in agreement with those of experimental mechanical tests. The approach proposed in this work could have interesting applications towards an ever more rational design of bone tissue engineering biomaterials and coatings, in view of the optimization of their mechanical properties for making them actually suitable for clinical applications. Copyright © 2012 Elsevier B.V. All rights reserved.

  16. STATIC AND DYNAMIC IN VITRO TEST OF BIOACTIVITY OF GLASS CERAMICS

    Directory of Open Access Journals (Sweden)

    JANA KOZÁNKOVÁ

    2011-06-01

    Full Text Available The bioactivity of glass ceramics from Li2O–SiO2–CaO–P2O5–CaF2 system, with different amount of fluorapatite expressed as P2O5 content, has been tested in vitro under static and dynamic regime. The paper reports the results of bioactivity test of glass ceramics in static and dynamic regime. XRD, SEM and EPMA analysis were used to characterise the sample as well as to detect the presence of new phase onto the surface of glass ceramics. The bioactivity, as demonstrated by the formation of new apatite layer, depends on P2O5 content and testing regime. In static regime, one can observe a fine microstructure of hydroxyapatite layer on the surface on glass ceramics samples. In dynamic regime, the formation rate of this layer seems to be retarded in comparison with that of static regime.

  17. Ceramic Laser Materials

    Energy Technology Data Exchange (ETDEWEB)

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

    2005-02-15

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

  18. Ceramic tubesheet design analysis

    Energy Technology Data Exchange (ETDEWEB)

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

    1996-06-01

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

  19. Laterally inherently thin amorphous-crystalline silicon heterojunction photovoltaic cell

    Energy Technology Data Exchange (ETDEWEB)

    Chowdhury, Zahidur R., E-mail: zr.chowdhury@utoronto.ca; Kherani, Nazir P., E-mail: kherani@ecf.utoronto.ca [Department of Electrical and Computer Engineering, University of Toronto, 10 King' s College Road, Toronto, Ontario M5S 3G4 (Canada)

    2014-12-29

    This article reports on an amorphous-crystalline silicon heterojunction photovoltaic cell concept wherein the heterojunction regions are laterally narrow and distributed amidst a backdrop of well-passivated crystalline silicon surface. The localized amorphous-crystalline silicon heterojunctions consisting of the laterally thin emitter and back-surface field regions are precisely aligned under the metal grid-lines and bus-bars while the remaining crystalline silicon surface is passivated using the recently proposed facile grown native oxide–plasma enhanced chemical vapour deposited silicon nitride passivation scheme. The proposed cell concept mitigates parasitic optical absorption losses by relegating amorphous silicon to beneath the shadowed metallized regions and by using optically transparent passivation layer. A photovoltaic conversion efficiency of 13.6% is obtained for an untextured proof-of-concept cell illuminated under AM 1.5 global spectrum; the specific cell performance parameters are V{sub OC} of 666 mV, J{sub SC} of 29.5 mA-cm{sup −2}, and fill-factor of 69.3%. Reduced parasitic absorption, predominantly in the shorter wavelength range, is confirmed with external quantum efficiency measurement.

  20. Laterally inherently thin amorphous-crystalline silicon heterojunction photovoltaic cell

    Science.gov (United States)

    Chowdhury, Zahidur R.; Kherani, Nazir P.

    2014-12-01

    This article reports on an amorphous-crystalline silicon heterojunction photovoltaic cell concept wherein the heterojunction regions are laterally narrow and distributed amidst a backdrop of well-passivated crystalline silicon surface. The localized amorphous-crystalline silicon heterojunctions consisting of the laterally thin emitter and back-surface field regions are precisely aligned under the metal grid-lines and bus-bars while the remaining crystalline silicon surface is passivated using the recently proposed facile grown native oxide-plasma enhanced chemical vapour deposited silicon nitride passivation scheme. The proposed cell concept mitigates parasitic optical absorption losses by relegating amorphous silicon to beneath the shadowed metallized regions and by using optically transparent passivation layer. A photovoltaic conversion efficiency of 13.6% is obtained for an untextured proof-of-concept cell illuminated under AM 1.5 global spectrum; the specific cell performance parameters are VOC of 666 mV, JSC of 29.5 mA-cm-2, and fill-factor of 69.3%. Reduced parasitic absorption, predominantly in the shorter wavelength range, is confirmed with external quantum efficiency measurement.

  1. Preparation of translucent YAG:Ce ceramics by reaction sintering

    Science.gov (United States)

    Michalik, D.; Sopicka-Lizer, M.; Pawlik, T.; Chrapoński, J.

    2012-05-01

    The paper presents preparation of YAG precursor powders mixture with ability for the reaction sintering at lower temperature. The powder mixture was mechanochemically processed and characterized for the specific surface area and crystallinity (XRD). Sintering experiments were performed on the batched powders, mechanochemically processed powders and as-synthesised YAG powders. XRD measurements and SEM/TEM studies were applied for characterization of the phase composition and development of YAG ceramics. Transmittance of the resultant ceramics was measured. It has been shown that YAG structure formed at 200 °C lower temperature in comparison to the reference specimen and contamination by the side phases (YAM, YAP) was limited. The best translucency was achieved for the reaction sintering of the mechanochemically processed powders.

  2. Synthesis of biomorphic SiC ceramic from bamboo charcoal.

    Science.gov (United States)

    Zhu, Jiangtao; Kwong, Fung Luen; Ng, Dickon Hang Leung

    2009-02-01

    Biomorphic SiC ceramic was successfully synthesized by reaction sintering between bamboo charcoal and a Si/SiO2 powder mixture. The charcoal was converted into an entirely SiC ceramic inherited with the original bamboo structure. Samples were characterized according to their crystallinity, morphology, microstructures and pore structures. We found that various morphological SiC structures were formed in different parts of the charcoal which depended on the morphology of the textures. The length of SiC nanowires were up to micron size. They were grown in the direction. The number of micropores in the converted biomorphic SiC was less than the original bamboo charcoal, but the pore diameter was larger.

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

    Science.gov (United States)

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

    2016-01-01

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

  4. Process of producing a ceramic matrix composite article and article formed thereby

    Science.gov (United States)

    Corman, Gregory Scot [Ballston Lake, NY; McGuigan, Henry Charles [Duanesburg, NY; Brun, Milivoj Konstantin [Ballston Lake, NY

    2011-10-25

    A CMC article and process for producing the article to have a layer on its surface that protects a reinforcement material within the article from damage. The method entails providing a body containing a ceramic reinforcement material in a matrix material that contains a precursor of a ceramic matrix material. A fraction of the reinforcement material is present and possibly exposed at a surface of the body. The body surface is then provided with a surface layer formed of a slurry containing a particulate material but lacking the reinforcement material of the body. The body and surface layer are heated to form the article by converting the precursor within the body to form the ceramic matrix material in which the reinforcement material is contained, and by converting the surface layer to form the protective layer that covers any fraction of the reinforcement material exposed at the body surface.

  5. Process of producing a ceramic matrix composite article and article formed thereby

    Science.gov (United States)

    Corman, Gregory Scot; McGuigan, Henry Charles; Brun, Milivoj Konstantin

    2010-05-04

    A CMC article and process for producing the article to have a layer on its surface that protects a reinforcement material within the article from damage. The method entails providing a body containing a ceramic reinforcement material in a matrix material that contains a precursor of a ceramic matrix material. A fraction of the reinforcement material is present and possibly exposed at a surface of the body. The body surface is then provided with a surface layer formed of a slurry containing a particulate material but lacking the reinforcement material of the body. The body and surface layer are heated to form the article by converting the precursor within the body to form the ceramic matrix material in which the reinforcement material is contained, and by converting the surface layer to form the protective layer that covers any fraction of the reinforcement material exposed at the body surface.

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

    Science.gov (United States)

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

    2007-12-01

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

  7. Effect of the processing parameters on the crystalline structure of lanthanide ortho tantalates

    Energy Technology Data Exchange (ETDEWEB)

    Siqueira, Kisla P.F.; Dias, Anderson, E-mail: anderson_dias@iceb.ufop.br [Universidade Federal de Ouro Preto (UFOP), MG (Brazil). Dept. de Quimica

    2014-08-15

    The influence of the synthesis parameters on the crystalline structures of ortho tantalate ceramics has been investigated. Powder materials were prepared by the solid-state reaction route. X-ray diffraction and Raman scattering measurements were employed to investigate the crystal structure of the produced materials. In this work, we analyzed three different examples in which the temperature and time were decisive on the final crystal structure of LnTaO{sub 4} compounds besides the lanthanide ionic size. Firstly, the thermal evolution for NdTaO{sub 4} samples showed that mixed crystal phases are formed up to 1100 °C, while well-crystallized M-NdTaO{sub 4} (I2/a) materials are obtained in temperatures higher than 1200 °C. Also, the influence of the synthesis time was investigated for the LaTaO{sub 4} ceramics: it was necessary 14 h to obtain samples in the P2{sub 1}/c structure. Finally, two polymorphs could be obtained for the DyTaO{sub 4} ceramics: P2/a and I2/a space groups were obtained at 1300 °C and 1500 °C, respectively. This study indicated that the temperature, time and lanthanide size are directly correlated with the crystalline arrangement of the ortho tantalate materials.(author)

  8. Ceramic colorant from untreated iron ore residue.

    Science.gov (United States)

    Pereira, Oscar Costa; Bernardin, Adriano Michael

    2012-09-30

    This work deals with the development of a ceramic colorant for glazes from an untreated iron ore residue. 6 mass% of the residue was added in suspensions (1.80 g/cm(3) density and 30s viscosity) of white, transparent and matte glazes, which were applied as thin layers (0.5mm) on engobeb and not fired ceramic tiles. The tiles were fired in laboratory roller kiln in a cycle of 35 min and maximum temperatures between 1050 and 1180°C. The residue and glazes were characterized by chemical (XRF) and thermal (DTA and optical dilatometry) analyses, and the glazed tiles by colorimetric and XRD analyses. The results showed that the colorant embedded in the transparent glaze results in a reddish glaze (like pine nut) suitable for the ceramic roof tile industry. For the matte and white glazes, the residue has changed the color of the tiles with temperature. Copyright © 2012 Elsevier B.V. All rights reserved.

  9. Bioactive glasses and glass-ceramics

    Directory of Open Access Journals (Sweden)

    de Aza, P. N.

    2007-04-01

    Full Text Available Since the late 1960´s, a great interest in the use of bioceramic materials for biomedical applications has been developed. In a previous paper, the authors reviewed crystalline bioceramic materials “sensus stricto”, it is to say, those ceramic materials, constituted for non-metallic inorganic compounds, crystallines and consolidates by thermal treatment of powders at high temperature. In the present review, the authors deal with those called bioactive glasses and glassceramics. Although all of them are also obtained by thermal treatment at high temperature, the first are amorphous and the second are obtained by devitrification of a glass, although the vitreous phase normally prevails on the crystalline phases. After an introduction to the concept of bioactive materials, a short historical review of the bioactive glasses development is made. Its preparation, reactivity in physiological media, mechanism of bonding to living tissues and mechanical strength of the bone-implant interface is also reported. Next, the concept of glass-ceramic and the way of its preparation are exposed. The composition, physicochemical properties and biological behaviour of the principal types of bioactive glasses and glass-ceramic materials: Bioglass®, Ceravital®, Cerabone®, Ilmaplant® and Bioverit® are also reviewed. Finally, a short review on the bioactive-glass coatings and bioactive-composites and most common uses of bioactive-glasses and glass-ceramics are carried out too.

    Desde finales de los años sesenta, se ha despertado un gran interés por el uso de los materiales biocerámicos para aplicaciones biomédicas. En un trabajo previo, los autores hicieron una revisión de los denominados materiales biocerámicos cristalinos en sentido estricto, es decir, de aquellos materiales, constituidos por compuestos inorgánicos no metálicos, cristalinos y consolidados mediante tratamientos térmicos a altas temperaturas. En el presente trabajo, los autores

  10. Masking ability of bi- and tri- laminate all-ceramic veneers on tooth-colored ceramic discs.

    Science.gov (United States)

    Farhan, Daniel; Sukumar, Smitha; von Stein-Lausnitz, Axel; Aarabi, Ghazal; Alawneh, Ahmad; Reissmann, Daniel R

    2014-01-01

    A predictable esthetic outcome is imperative when placing ceramic veneers. Discolored teeth pose a major challenge as sufficient material thickness is required to achieve a good esthetic result. There is limited evidence in the literature that compares the masking ability of multi-laminate veneers. The aim of this in-vitro study was to compare the masking ability of bi-laminate (BL) and tri-laminate (TL) all-ceramic veneers cemented on tooth-colored ceramic discs. A total of 40 veneers (shade A1, 10-mm diameter, 0.8-mm thick) were manufactured-20 BL veneers (0.4-mm pressable ceramic coping veneered with 0.4-mm thick enamel layer) and 20 TL veneers (0.4-mm coping veneered with 0.2-mm thick opaque interlayer and 0.2-mm thick enamel layer). A bonding apparatus was utilized to adhesively cement all veneers on the ceramic discs (shade A1), simulating teeth of light and dark color. The resulting groups (N = 10 each) were the reference groups (shade A1 ceramic base) BL-1 and TL-1 veneers, and the test groups (shade A4 ceramic base) BL-4 and TL-4 veneers. The color of the cemented veneers was measured using a spectrophotometer. The data were converted to CIE L*a*b* coordinates, and ΔE* were calculated to allow for statistical analysis. The color differences between the samples with the A1 and A4 ceramic bases were significantly lower when covered with TL veneers (mean ΔE*: 3.2 units) than with BL veneers (mean ΔE*: 4.0 units: p veneers. The 0.8-mm thick TL veneer was able to mask darker tooth-colored ceramic disc within clinically acceptable limits. Increased understanding of the masking ability of ceramics and of color science is necessary in these esthetically aware times. Providing tri-laminate veneers for darker colored teeth seems to result in more predictable esthetical results than when using bi-laminate veneers. Patients with discolored/darker teeth may benefit from a more predictable esthetic result when teeth restored with tri-laminate rather than bi

  11. Grain boundaries in ceramics and ceramic-metal interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Clarke, D.R.; Wolf, D.

    1986-01-01

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

  12. The comparison of phosphate-titanate-silicate layers on the titanium and Ti6Al4V alloy base.

    Science.gov (United States)

    Rokita, M

    2011-08-15

    The studied layers were composed of two parts: titanate-silicate underlayer for better adhesion and titanate-phosphate-silicate layers for potential bioparameters. The layers with different amounts of hydroxyapatite were deposited on titanium and Ti6Al4V alloy substrates using dipping sol-gel method and electrophoresis. The selection of sol/suspension composition, deposition time and heat treatment conditions have the decisive influence on the layers parameters. The obtained layers should be very thin and almost amorphous. The specific nature of ceramic layers on the metal substrates excludes the use of some measurements methods or makes it difficult to interpret the measurement results. All the obtained samples were compared using XRD analysis data (GID technique), SEM with EDX measurements and FTIR spectroscopy (transmission and reflection techniques) before and after soaking in simulated body fluid. FTIR spectroscopy with mathematical treatment of the spectra (BIO-RAD Win-IR program, Arithmetic-subtract function) was used to detect the increase or decrease of any phosphate phases during SBF soaking. Based on the FTIR results the processes of hydroxyapatite (HAp) growth or layer dissolution were estimated. The layers deposited on titanium substrate are more crystalline then the ones deposited on Ti6Al4V. During SBF soaking process the growth of small amount of microcrystalline carbonate hydroxyapatite was observed on titanium substrate. The layer on Ti6Al4V base contained amorphous carbonate apatite. During heating treatment above about 870-920 K this apatite transforms into carbonate hydroxyapatite. The Ti6Al4V substrate seems to be more advantageous in context of potentially bioactive materials obtaining. Copyright © 2010 Elsevier B.V. All rights reserved.

  13. Inward Cationic Diffusion and Percolation Transition in Glass-Ceramics

    DEFF Research Database (Denmark)

    Smedsklaer, Morten Mattrup; Yue, Yuanzheng; Mørup, Steen

    2010-01-01

    We show the quantitative correlation between the degree of crystallization and the cationic diffusion extent in iron-containing diopside glass–ceramics at the glass transition temperature. We find a critical degree of crystallization, above which the diffusion extent sharply drops with the degree...... of crystallization. Below the critical value, the diffusion extent decreases only slightly with the degree of crystallization. No cationic diffusion is observed in the fully crystalline materials. The critical value might be associated with a percolation transition from an interconnected to a disconnected glass...

  14. Microtensile bond strength of different components of core veneered all-ceramic restorations. Part 3: double veneer technique

    NARCIS (Netherlands)

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

    2008-01-01

    Purpose: The bond strength of zirconia veneer has been considered a weak link in the layered all-ceramic restoration. In a previous study, this bond was improved using a new category of veneering ceramics adopting the pressing technique; however, the resulting esthetic quality lacked the individual

  15. Pockels effect of silicate glass-ceramics: Observation of optical modulation in Mach-Zehnder system.

    Science.gov (United States)

    Yamaoka, Kazuki; Takahashi, Yoshihiro; Yamazaki, Yoshiki; Terakado, Nobuaki; Miyazaki, Takamichi; Fujiwara, Takumi

    2015-07-17

    Silicate glass has been used for long time because of its advantages from material's viewpoint. In this paper, we report the observation of Pockels effect by Mach-Zehnder interferometer in polycrystalline ceramics made from a ternary silicate glass via crystallization due to heat-treatment, i.e., glass-ceramics. Since the silicate system is employed as the precursor, merits of glass material are fully utilized to fabricate the optical device component, in addition to that of functional crystalline material, leading us to provide an electro-optic device, which is introducible into glass-fiber network.

  16. Support for the Armor Ceramics symposium at the 40th International Conference on Advanced Ceramics and Composites

    Science.gov (United States)

    2016-05-09

    AM Break 10:20-10:40 AM ICACC-S4-017-2016. Multi-layer ceramic armors from bio inspired, structural templates G. Smith; G. Dwivedi; S. Sampath...M. Kubo 5:30 PM-8:00 PM ICACC-S1-P032-2016. Chemical Reaction Process of Si3N4 under Water Lubrication by Tight-Binding Quantum Chemical...R. Podor; N. Clavier; J. Léchelle; N. Dacheaux 5:30 PM-8:00 PM ICACC-EMERG-WW-P070-2016. Soft Ceramics and High Temperature Lubrication P

  17. The behavior of multilayer ceramic protections at quick thermal shock

    Directory of Open Access Journals (Sweden)

    Alexandru MIHAILESCU

    2013-06-01

    Full Text Available Protective layers of “hot parts” of the turbo engines as well as co-generative systems of energy industry are exposed to a combination of wear factors which may act together at high values.The main goal of the paper is the behavior of some advanced layers, duplex and triplex, multifunctional, ceramics in relation to the most complex wear factor and disturbing as well, the quick thermal shock.The quick thermal shock test installation designed and constructed by the INCAS covers the domain of some high gradients of heating/cooling and is currently integrated in a network of European infrastructure that evaluates the properties of functional layers for turbo engines.Micro-structure inter- and intra- facial changes gradually induced in ceramic structures are highlighted and on this basis their ranking and selection for application on physical parts are established.

  18. Seal between metal and ceramic conduits

    Energy Technology Data Exchange (ETDEWEB)

    Underwood, Richard Paul; Tentarelli, Stephen Clyde

    2015-02-03

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

  19. Development of Sesquioxide Ceramic for High Energy Lasers

    Science.gov (United States)

    2015-05-25

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

  20. Tailored Ceramics for Laser Applications

    Energy Technology Data Exchange (ETDEWEB)

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

    2007-12-10

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

  1. Laser Micromachining of Ceramics

    OpenAIRE

    SCITI, Diletta; Bellosi, Alida

    2011-01-01

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

  2. Statistic><Ceramics

    DEFF Research Database (Denmark)

    Hansen, Flemming Tvede

    2008-01-01

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

  3. Ceramic stationary gas turbine

    Energy Technology Data Exchange (ETDEWEB)

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

    1995-10-01

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

  4. Dental ceramics: a current review.

    Science.gov (United States)

    Lawson, Nathaniel C; Burgess, John O

    2014-03-01

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

  5. Color match of two different ceramic systems to selected shades of one shade guide.

    Science.gov (United States)

    Corciolani, Gabriele; Vichi, Alessandro; Louca, Chris; Ferrari, Marco

    2011-03-01

    There are no consistent indications given by dental manufacturers on how to layer ceramics to achieve a color match to a shade selected from a dental shade guide. The technique for ceramic layering relies primarily on the skill and experience of ceramists and is not easily predictable. The purpose of this study was to evaluate, using a clinical spectrophotometer, the ability to color match shades selected with the 3D-Master shade guide using 2 different ceramic systems. Two ceramic systems were selected for this study, the VITA Omega 900 and VITA VM 13. For both systems, shades 2M3, 3M2, 4M2 of the VITA 3D-Master shade guide were selected. Thirty ceramic discs, 15 mm in diameter, were fabricated with different layer thickness ratios of opaque dentin, dentin, and enamel, maintaining a constant overall thickness. A clinical spectrophotometer (VITA Easyshade) was used for color comparison. The measured ΔE values were statistically analyzed with a 3-way ANOVA and the Tukey HSD test (α=.05). The 3-way ANOVA showed that the ceramic system (P3D-Master shade guide to be within the limits for clinical acceptability (ΔE≤ 3.3). VM 13 showed a statistically better color match. The layering scheme influenced the definitive color of the restoration. Copyright © 2011 The Editorial Council of the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.

  6. Research Opportunities in Crystalline Silicon Photovoltaics for the 21st Century

    Energy Technology Data Exchange (ETDEWEB)

    Atwater, Harry A.; Ciszek, Ted; Feldman, Leonard C.; Gee, James; Rohatgi, Ajeet; Sopori, Bhushan

    1999-07-28

    Crystalline silicon continues to be the dominant semiconductor material used for terrestrial photovoltaics. This paper discusses the scientific issues associated with silicon photovoltaics processing, and cell design that may yield cell and module performance improvements that are both evolutionary and revolutionary in nature. We first survey critical issues in ''thick'' crystalline silicon photovoltaics, including novel separations processes for impurity removal, impurity and defect fundamentals, interface passivation, the role of hydrogen. Second, we outline emerging opportunities for creation of a very different ''thin-layer'' silicon cell structure, including the scientific issues and engineering challenges associated with thin-layer silicon processing and cell design.

  7. Porous biomorphic silicon carbide ceramics coated with hydroxyapatite as prospective materials for bone implants.

    Science.gov (United States)

    Gryshkov, Oleksandr; Klyui, Nickolai I; Temchenko, Volodymyr P; Kyselov, Vitalii S; Chatterjee, Anamika; Belyaev, Alexander E; Lauterboeck, Lothar; Iarmolenko, Dmytro; Glasmacher, Birgit

    2016-11-01

    Porous and cytocompatible silicon carbide (SiC) ceramics derived from wood precursors and coated with bioactive hydroxyapatite (HA) and HA-zirconium dioxide (HA/ZrO2) composite are materials with promising application in engineering of bone implants due to their excellent mechanical and structural properties. Biomorphic SiC ceramics have been synthesized from wood (Hornbeam, Sapele, Tilia and Pear) using a forced impregnation method. The SiC ceramics have been coated with bioactive HA and HA/ZrO2 using effective gas detonation deposition approach (GDD). The surface morphology and cytotoxicity of SiC ceramics as well as phase composition and crystallinity of deposited coatings were analyzed. It has been shown that the porosity and pore size of SiC ceramics depend on initial wood source. The XRD and FTIR studies revealed the preservation of crystal structure and phase composition of in the HA coating, while addition of ZrO2 to the initial HA powder resulted in significant decomposition of the final HA/ZrO2 coating and formation of other calcium phosphate phases. In turn, NIH 3T3 cells cultured in medium exposed to coated and uncoated SiC ceramics showed high re-cultivation efficiency as well as metabolic activity. The recultivation efficiency of cells was the highest for HA-coated ceramics, whereas HA/ZrO2 coating improved the recultivation efficiency of cells as compared to uncoated SiC ceramics. The GDD method allowed generating homogeneous HA coatings with no change in calcium to phosphorus ratio. In summary, porous and cytocompatible bio-SiC ceramics with bioactive coatings show a great promise in construction of light, robust, inexpensive and patient-specific bone implants for clinical application. Copyright © 2016 Elsevier B.V. All rights reserved.

  8. Performance of new ceramic scintillators for gamma- and x-ray detection

    Science.gov (United States)

    Wisniewski, Dariusz J.; Boatner, Lynn A.; Neal, John S.; Jellison, Gerald E.; Ramey, Joanne O.; North, Andrea; Wisniewska, Monika; Lempicki, Aleksander; Brecher, Charlie; Glodo, Jaroslaw

    2007-09-01

    Ceramic materials show significant promise for the production of reasonably priced, large-size scintillators. Ceramics have recently received a great deal of attention in the field of materials for laser applications, and the technology for fabricating high-optical-quality polycrystalline ceramics of cubic materials has been well developed. The formation of transparent ceramics of non-cubic materials is, however, much more difficult as a result of birefringence effects in differently oriented grains. Here, we will describe the performance of a few new ceramics developed for the detection of gamma- and x-ray radiation. Results are presented for ceramic analogs of three crystalline materials - cubic Lu IIO 3, and non-cubic LaBr 3, and Lu IISiO 5 or LSO (hexagonal, and monoclinic structures, respectively). The impact of various sintering, hot-pressing and post-formation annealing procedures on the light yield, transparency, and other parameters, will be discussed. The study of LaBr 3:Ce shows that fairly translucent ceramics of rare-earth halides can be fabricated and they can reach relatively high light yield values. Despite the fact that no evidence for texturing has been found in our LSO:Ce ceramic microstructures, the material demonstrates a surprisingly high level of translucency or transparency. While the scintillation of LSO:Ce ceramic reaches a light yield level of about 86 % of that of a good LSO:Ce single crystal, its decay time is even faster, and the long term afterglow is lower than in LSO single crystals.

  9. The layer by layer selective laser synthesis of ruby

    Directory of Open Access Journals (Sweden)

    Vlasova M.

    2010-01-01

    Full Text Available In the work, features of the layer-by-layer selective laser synthesis (SLS of ruby from an Al2O3-Cr2O3 mixture are considered depending on the irradiation power, the laser beam traverse speed, the height and amount of the backfill of powder layers. It has been established that, under irradiation, a track consisting of polycrystalline textured ruby forms. The morphology of the surface of the track and its crystalline structure are determined by the irradiation conditions.

  10. The effect of repeated firings on the color change and surface roughness of dental ceramics

    Science.gov (United States)

    Yılmaz, Kerem; Ozturk, Caner

    2014-01-01

    PURPOSE The color of the ceramic restorations is affected by various factors such as brand, thickness of the layered the ceramic, condensation techniques, smoothness of surface, number of firings, firing temperature and thickness of dentin. The aim of this study was to evaluate the color change and surface roughness in dental porcelain with different thicknesses during repeated firings. MATERIALS AND METHODS Disc-shaped (N=21) metal-ceramic samples (IPS Classic; Ivoclar Vivadent; Shaar, Liechtenstein) with different thickness were exposed to repeated firings. Color measurement of the samples was made using a colorimeter and profilometer was used to determine surface roughness. ANOVA and Tukey tests with repeated measurements were used for statistical analysis. RESULTS The total thickness of the ceramics which is less than 2 mm significantly have detrimental effect on the surface properties and color of porcelains during firings (Pdental ceramics and should be avoided. PMID:25177475

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

    Science.gov (United States)

    Quran, Firas Al; Haj-Ali, Reem

    2012-03-01

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

  12. Ceramic membranes for gas separation

    Energy Technology Data Exchange (ETDEWEB)

    Vincente-Mingarro, I.M. de; Pitarch, J.A. [Tecnologia y Gestion de la Innovacion, Madrid (Spain)

    1998-11-01

    The project is being carried out jointly by TGI, S.A., CIEMAT and CSIC-ICM to develop and evaluate new inorganic membranes of a ceramic type, with nanometric pore size for separation of contaminants and fuel enrichment, in gas mixtures from coal gasification. In order to achieve both the highest active and selective surface, a candle (150 mm length and 60 mm in diameter), with 30-40 % porosity and pore sizes of {lt}1 {mu}m was developed. The processing steps include the slip-casting of the first layer (porous support) in a way than after thermal treatment (1400-1600{degree}C) the desirable shape dimensions, strength, porosity and pore size were obtained. Then the support was dipped successively (colloidal filtration over the casting porous piece) in an appropriate suspension of alumina with lower grain size. The top layer was obtained by the sol-gel process so that through successive setting and heat treatment the pores were reduced to the nanometre size. CVD and CVI techniques were set up to develop membranes for gas separation with a high selectivity level. Experimental chemical infiltration `Membranes Development` on porous substrates has been achieved on disk and candle-shaped materials. Characterisation was by spectrophotometry (IRS). Kinetic studies of coating in order to find out reproducible conditions at low temperature were also carried out. Uniform recovery over the whole membrane surface is wanted. The CIEMAT`s Hot Gas Separation Plant (HGSP) works with gas mixtures at a maximum design temperature 773 K and pressures up to 50 bar. It comprises: a gas supply unit equipped with flow, temperature and pressure measuring and control systems; a heating system within the membrane which must be leak proof for high pressures; and an in-line gas chromatography system thus allowing the chemical composition of the gas entering, permeated and retained to be measured. 7 figs.

  13. Crystalline Structure, Defect Chemistry and Room Temperature Colossal Permittivity of Nd-doped Barium Titanate

    Science.gov (United States)

    Sun, Qiaomei; Gu, Qilin; Zhu, Kongjun; Jin, Rongying; Liu, Jinsong; Wang, Jing; Qiu, Jinhao

    2017-02-01

    Dielectric materials with high permittivity are strongly demanded for various technological applications. While polarization inherently exists in ferroelectric barium titanate (BaTiO3), its high permittivity can only be achieved by chemical and/or structural modification. Here, we report the room-temperature colossal permittivity (~760,000) obtained in xNd: BaTiO3 (x = 0.5 mol%) ceramics derived from the counterpart nanoparticles followed by conventional pressureless sintering process. Through the systematic analysis of chemical composition, crystalline structure and defect chemistry, the substitution mechanism involving the occupation of Nd3+ in Ba2+ -site associated with the generation of Ba vacancies and oxygen vacancies for charge compensation has been firstly demonstrated. The present study serves as a precedent and fundamental step toward further improvement of the permittivity of BaTiO3-based ceramics.

  14. Crystalline Structure, Defect Chemistry and Room Temperature Colossal Permittivity of Nd-doped Barium Titanate.

    Science.gov (United States)

    Sun, Qiaomei; Gu, Qilin; Zhu, Kongjun; Jin, Rongying; Liu, Jinsong; Wang, Jing; Qiu, Jinhao

    2017-02-13

    Dielectric materials with high permittivity are strongly demanded for various technological applications. While polarization inherently exists in ferroelectric barium titanate (BaTiO3), its high permittivity can only be achieved by chemical and/or structural modification. Here, we report the room-temperature colossal permittivity (~760,000) obtained in xNd: BaTiO3 (x = 0.5 mol%) ceramics derived from the counterpart nanoparticles followed by conventional pressureless sintering process. Through the systematic analysis of chemical composition, crystalline structure and defect chemistry, the substitution mechanism involving the occupation of Nd3+ in Ba2+ -site associated with the generation of Ba vacancies and oxygen vacancies for charge compensation has been firstly demonstrated. The present study serves as a precedent and fundamental step toward further improvement of the permittivity of BaTiO3-based ceramics.

  15. Translucency of ceramic materials for CEREC CAD/CAM system.

    Science.gov (United States)

    Vichi, Alessandro; Carrabba, Michele; Paravina, Rade; Ferrari, Marco

    2014-01-01

    To compare translucency of the ceramic materials (CEREC CAD/CAM). Fifteen ceramic materials for CEREC CAD/CAM system were evaluated: IPS e.max HT/LT/MO, ZirCAD, Empress HT/LT; VITA Mark II, VITA AL; VITA YZ, VITA In-Ceram Spinell/Alumina/Zirconia; and Sirona InCoris AL; Sirona InCoris ZI/TZI. Specimens (0.5-mm and 1.0-mm thick; n = 10 each material) were cut from commercial blocks using a water-cooled diamond saw. Contrast ratio (CR = YB /YW ) was measured using a spectrophotometer with an integrating sphere. Kruskal-Wallis one way analysis of variance was performed followed by Dunn's multiple test for post-hoc. CR varied from 0.35 to 1.00 and from 0.48 to 1.00 for 0.5 mm and 1.0 mm thicknesses, respectively. CR increased in the following order: IPS e.max HT (most translucent-least opaque), IPS Empress HT, VITA Mark II, IPS Empress LT, IPS e.max LT, In-Ceram Spinell, IPS e.max MO, VITA YZ, InCoris TZI, IPS e.max ZirCAD, InCoris ZI, In-Ceram Alumina, VITA AL, InCoris AL, and In-Ceram Zirconia (least translucent-most opaque). The null hypothesis has been rejected because tested materials exhibited a wide range of CR. Translucency needs to be taken into account in different clinical situations, including considerations associated with thickness of restoration and/or particular layers. A wide range of translucency was identified for the ceramic materials tested. This variability has to be taken into account for the selection of the materials in different clinical situations also related to the thickness clinically required. © 2014 Wiley Periodicals, Inc.

  16. Biaxial flexural strength of bilayered zirconia using various veneering ceramics.

    Science.gov (United States)

    Chantranikul, Natravee; Salimee, Prarom

    2015-10-01

    The aim of this study was to evaluate the biaxial flexural strength (BFS) of one zirconia-based ceramic used with various veneering ceramics. Zirconia core material (Katana) and five veneering ceramics (Cerabien ZR; CZR, Lava Ceram; LV, Cercon Ceram Kiss; CC, IPS e.max Ceram; EM and VITA VM9; VT) were selected. Using the powder/liquid layering technique, bilayered disk specimens (diameter: 12.50 mm, thickness: 1.50 mm) were prepared to follow ISO standard 6872:2008 into five groups according to veneering ceramics as follows; Katana zirconia veneering with CZR (K/CZR), Katana zirconia veneering with LV (K/LV), Katana zirconia veneering with CC (K/CC), Katana zirconia veneering with EM (K/EM) and Katana zirconia veneering with VT (K/VT). After 20,000 thermocycling, load tests were conducted using a universal testing machine (Instron). The BFS were calculated and analyzed with one-way ANOVA and Tukey HSD (α=0.05). The Weibull analysis was performed for reliability of strength. The mode of fracture and fractured surface were observed by SEM. It showed that K/CC had significantly the highest BFS, followed by K/LV. BFS of K/CZR, K/EM and K/VT were not significantly different from each other, but were significantly lower than the other two groups. Weibull distribution reported the same trend of reliability as the BFS results. From the result of this study, the BFS of the bilayered zirconia/veneer composite did not only depend on the Young's modulus value of the materials. Further studies regarding interfacial strength and sintering factors are necessary to achieve the optimal strength.

  17. Clinical Aspects of Combination of Ceramic and Acrylic Occlusal Surfaces

    Directory of Open Access Journals (Sweden)

    Z. Ozhohan

    2017-03-01

    Full Text Available The objective of the research was to develop and substantiate the methods of constructing the occlusal surfaces when manufacturing aesthetic fixed restorations through the combination of different materials. Materials and methods. The study included 65 patients with ceramic and acrylic occlusal surfaces of aesthetic fixed dental prostheses. Group I included 21 patients with a combination of ceramic and acrylic occlusal surfaces. Group II included 22 patients with a combination of ceramic occlusal surfaces. Group III included 22 patients with a combination of acrylic occlusal surfaces. The patients were observed 3, 6 and 12 months after prosthetic repair. Results. The greatest increase in the occlusal contact surface area of fixed restorations was observed in Group I, that is, when combining dental prostheses with ceramic and acrylic occlusal surfaces. Considering uneven abrasion of the occlusal surfaces, we do not recommend to combine different materials when veneering the occlusal surface of the antagonistic teeth. Conclusions. This study demonstrated the important role of the correct combination of materials when veneering the occlusal surfaces. Physical and chemical properties of materials, namely the abrasion resistance play a significant role in the long-term denture functioning. The smallest increase in the occlusal contact surface area was observed in Group II when combining ceramic occlusal surfaces. It was due to a good abrasion resistance of ceramics as compared to acrylic resin as well as the presence of the glazed layer which prevents the premature abrasion of the occlusal surfaces of the antagonistic teeth due to lower surface roughness. The combination of acrylic resin and ceramics when constructing the occlusal surfaces of fixed restorations in Group I demonstrated the highest rate of the increase in the occlusal contact surface area – 9.93%. It was due to a low hardness of acrylic resin and its high surface roughness. In

  18. Silicone Resin Applications for Ceramic Precursors and Composites

    Directory of Open Access Journals (Sweden)

    Masaki Narisawa

    2010-06-01

    Full Text Available This article reviews the applications of silicone resins as ceramic precursors. The historical background of silicone synthesis chemistry is introduced to explain the production costs and supply availability of various silicones. Thermal degradation processes of silicones are classified in terms of the main chain structure and cyclic oligomer expulsion process, which determine the resulting ceramic yield and the chemical composition. The high temperature decomposition of Si-O-C beyond 1,400 °C in an inert atmosphere and formation of a protective silica layer on material surfaces beyond 1,200 °C in an oxidative atmosphere are discussed from the viewpoints of the wide chemical composition of the Si-O-C materials. Applications of the resins for binding agents, as starting materials for porous ceramics, matrix sources with impregnation, fiber spinning and ceramic adhesions are introduced. The recent development of the process of filler or cross-linking agent additions to resin compounds is also introduced. Such resin compounds are useful for obtaining thick coatings, MEMS parts and bulk ceramics, which are difficult to obtain by pyrolysis of simple organometallic precursors without additives.

  19. Light scattering of thin azobenzene side-chain polyester layers

    DEFF Research Database (Denmark)

    Kerekes, Á.; Lörincz, E.; Ramanujam, P.S.

    2002-01-01

    Light scattering properties of liquid crystalline and amorphous azobenzene side-chain polyester layers used for optical data storage were examined by means of transmissive scatterometry. Comparative experiments show that the amorphous polyester has significantly lower light scattering characteris...... for the domain size in thin liquid crystalline polyester layers being responsible for the dominant light scattering. The characteristic domain Sizes obtained from the Fourier transformation of polarization microscopic Pictures confirm these values.......Light scattering properties of liquid crystalline and amorphous azobenzene side-chain polyester layers used for optical data storage were examined by means of transmissive scatterometry. Comparative experiments show that the amorphous polyester has significantly lower light scattering...... characteristics than the liquid crystalline polyester. The amorphous samples have negligible polarization part orthogonal to the incident beam. the liquid crystalline samples have relative high orthogonal polarization part in light scattering, The light scattering results can be used to give a lower limit...

  20. An evaluation of the processing conditions, structure, and properties (biaxial flexural strength and antibacterial efficacy) of sintered strontium-zinc-silicate glass ceramics.

    Science.gov (United States)

    Looney, Mark; Shea, Helen O'; Gunn, Lynda; Crowley, Dolores; Boyd, Daniel

    2013-05-01

    The use of artificial bone grafts has increased in order to satisfy a growing demand for bone replacement materials. Initial mechanical stability of synthetic bone grafts is very advantageous for certain clinical applications. Coupled with the advantage of mechanical strength, a material with inherent antibacterial properties would be very beneficial. A series of strontium-doped zinc silicate (Ca-Sr-Na-Zn-Si) glass ceramics have been characterized in terms of their crystalline structure, biaxial flexural strength and antibacterial efficacy based on the identification of optimum sintering conditions. All three glass ceramics, namely, BT110, BT111, and BT112 were found to be fully crystalline, with BT111 and BT112 comprising of biocompatible crystalline phases. The biaxial flexural strengths of the three glass ceramics ranged from 70 to 149 MPa and were shown to be superior to those of clinically established ceramics in dry conditions and following incubation in simulated physiological conditions. The bacteriostatic effect for each glass ceramic was also established, where BT112 showed an inhibitory effect against three of the most common bacteria found at implantation sites, namely, Enterococcus faecalis, methicillin-resistant Staphylococcus aureus (MRSA), and Pseudomonas aeruginosa. The results of the evaluation suggest that the materials studied offer advantages over current clinical materials and indicate the potential suitability of the glass ceramics as therapeutic bone grafts.

  1. Ceramic laminates with tailored residual stresses

    Directory of Open Access Journals (Sweden)

    Baudín, C.

    2009-12-01

    Full Text Available Severe environments imposed by new technologies demand new materials with better properties and ensured reliability. The intrinsic brittleness of ceramics has forced scientists to look for new materials and processing routes to improve the mechanical behaviour of ceramics in order to allow their use under severe thermomechanical conditions. The laminate approach has allowed the fabrication of a new family of composite materials with strength and reliability superior to those of monolithic ceramics with microstructures similar to those of the constituent layers. The different ceramic laminates developed since the middle 1970´s can be divided in two large groups depending on whether the development of residual stresses between layers is the main design tool. This paper reviews the developments in the control and tailoring of residual stresses in ceramic laminates. The tailoring of the thickness and location of layers in compression can lead to extremely performing structures in terms of strength values and reliability. External layers in compression lead to the strengthening of the structure. When relatively thin and highly compressed layers are located inside the material, threshold strength, crack bifurcation and crack arrest during fracture occur.

    Las severas condiciones de trabajo de las nuevas aplicaciones tecnológicas exigen el uso de materiales con mejores propiedades y alta fiabilidad. La potencialidad de uso de materiales frágiles, como los cerámicos, en estas aplicaciones exige el desarrollo de nuevos materiales y métodos de procesamiento que mejoren su comportamiento mecánico. El concepto de material laminado ha permitido la fabricación de una nueva familia de materiales con tensiones de fractura y fiabilidad superiores a las de materiales monolíticos con microestructuras similares a las de las láminas que conforman el laminado. Los distintos materiales laminados desarrollados desde mediados de los años 70 se pueden

  2. Chemical and Microstructural Changes in Metallic and Ceramic Materials Exposed to Venusian Surface Conditions

    Science.gov (United States)

    Costa, Gustavo C. C.; Jacobson, Nathan S.; Lukco, Dorothy; Hunter, Gary W.; Nakley, Leah; Radoman-Shaw, Brandon G.; Harvey, Ralph P.

    2017-01-01

    The chemical and microstructural behavior of steels (304, 310, 316, and 1018), nickel-based alloys (beta-NiAl, G30, and 625), gold, coatings (4YSZ, SilcoNert(TradeMark) 1040 (SilcoTek Co.), Dursan(TradeMark)? (SilcoTek Co.), and porcelain), and bulk ceramics (alpha-Al2O3, fused quartz, beta-SiC, and alpha-Si3N4) were probed after exposure to supercritical fluid with temperature, pressure, and composition mimicking the Venus lower atmosphere. Exposures were carried out in the Glenn Extreme Environments Rig (GEER) chamber with the Venusian gas mixture (96.5% CO2, 3.5% N2, 30 ppm H2O, 150 ppm SO2, 28 ppm CO, 15 ppm OCS, 3 ppm H2S, 0.5 ppm HCl, and 5 ppb HF) at 92 bar (1330 psi) and 467 C (873 F) for durations of 10 and 42 days. An additional 21-day exposure was done to stainless steel uncoated and coated with SilcoNert(TradeMark) and Dursan(TradeMark). Samples were characterized before and after the experiment by gravimetric analysis, X-ray diffraction, X-ray photoelectron and Auger electron spectroscopies, and cross section electron microscopy analysis. All steels exposed for 10 and 42 days formed double-layered scales consisting mainly of metal (Cr, Fe, Ni) oxides and sulfides showing different chemistry, microstructure, and crystalline phases. The alloys G30 and 625 formed double-layered scales consisting mainly of nickel sulfides. After 10 days, the beta-NiAl exhibited no detectable scale, suggesting only a very thin film was formed. The 304 and 316 stainless steels coated with 4YSZ that were exposed for 10 and 42 days exhibited no significant oxidation. Steel 1018 coated with 4YSZ exhibited a corrosion scale of iron and/or chromium oxide formed at the base of the alloy. The 304 steel coated with porcelain did not exhibit corrosion, although the coating exhibited recession. SilcoNert(TradeMark) exposed for 10 and 42 days exhibited recession, although no oxidation was found to occur at the base of the alloy. Stainless steel 316 coated with Dursan

  3. Failure modes and materials design for biomechanical layer structures

    Science.gov (United States)

    Deng, Yan

    Ceramic materials are finding increasing usage in the area of biomechanical replacements---dental crowns, hip and bone implants, etc.---where strength, wear resistance, biocompatibility, chemical durability and even aesthetics are critical issues. Aesthetic ceramic crowns have been widely used in dentistry to replace damaged or missing teeth. However, the failure rates of ceramic crowns, especially all-ceramic crowns, can be 1%˜6% per year, which is not satisfactory to patients. The materials limitations and underlying fracture mechanisms of these prostheses are not well understood. In this thesis, fundamental fracture and damage mechanisms in model dental bilayer and trilayer structures are studied. Principle failure modes are identified from in situ experimentation and confirmed by fracture mechanics analysis. In bilayer structures of ceramic/polycarbonate (representative of ceramic crown/dentin structure), three major damage sources are identified: (i) top-surface cone cracks or (ii) quasiplasticity, dominating in thick ceramic bilayers; (iii) bottom-surface radial cracks, dominating in thin ceramic bilayers. Critical load P for each damage mode are measured in six dental ceramics: Y-TZP zirconia, glass-infiltrated zirconia and alumina (InCeram), glass-ceramic (Empress II), Porcelain (Mark II and Empress) bonded to polymer substrates, as a function of ceramic thickness d in the range of 100 mum to 10 mm. P is found independent of d for mode (i) and (ii), but has a d 2 relations for mode (iii)---bottom surface radial cracking. In trilayer structures of glass/core-ceramic/polycarbonate (representing veneer porcelain/core/dentin structures), three inner fracture origins are identified: radial cracks from the bottom surface in the (i) first and (ii) second layers; and (iii) quasiplasticity in core-ceramic layer. The role of relative veneer/core thickness, d1/d 2 and materials properties is investigated for three core materials with different modulus (114--270GPa

  4. Elaboration of new ceramic composites containing glass fibre production wastes

    Directory of Open Access Journals (Sweden)

    Rozenstrauha, I.

    2013-04-01

    Full Text Available Two main by-products or waste from the production of glass fibre are following: sewage sludge containing montmorillonite clay as sorbent material and ca 50% of organic matter as well as waste glass from aluminiumborosilicate glass fibre with relatively high softening temperature (> 600 ºC. In order to elaborate different new ceramic products (porous or dense composites the mentioned by-products and illitic clay from two different layers of Apriki deposit (Latvia with illite content in clay fraction up to 80-90% was used as a matrix. The raw materials were investigated by differential-thermal (DTA and XRD analysis. Ternary compositions were prepared from mixtures of 15–35 wt % of sludge, 20 wt % of waste glass and 45–65 wt % of clay and the pressed green bodies were thermally treated in sintering temperature range from 1080 to 1120 ºC in different treatment conditions. Materials produced in temperature range 1090–1100 ºC with the most optimal properties - porosity 38-52%, water absorption 39–47% and bulk density 1.35–1.67 g/cm3 were selected for production of porous ceramics and materials showing porosity 0.35–1.1%, water absorption 0.7–2.6 % and bulk density 2.1–2.3 g/cm3 - for dense ceramic composites. Obtained results indicated that incorporation up to 25 wt % of sewage sludge is beneficial for production of both ceramic products and glass-ceramic composites according to the technological properties. Structural analysis of elaborated composite materials was performed by scanning electron microscopy(SEM. By X-ray diffraction analysis (XRD the quartz, diopside and anorthite crystalline phases were detected.Durante la obtención de ciertas fibras de vidrio se generan dos subproductos o residuos principalmente: Lodo de arcilla montmorillonítica capaz de adsorber el 50 % de materia orgánica y un vidrio silicato alumínico con temperatura de reblandecimiento relativamente alta (> 600 ºC. Con el fin de elaborar nuevos

  5. Mechanical performance of a biocompatible biocide soda-lime glass-ceramic.

    Science.gov (United States)

    López-Esteban, S; Bartolomé, J F; Dí Az, L A; Esteban-Tejeda, L; Prado, C; López-Piriz, R; Torrecillas, R; Moya, J S

    2014-06-01

    A biocompatible soda-lime glass-ceramic in the SiO2-Na2O-Al2O3-CaO-B2O3 system containing combeite and nepheline as crystalline phases, has been obtained at 750°C by two different routes: (i) pressureless sintering and (ii) Spark Plasma Sintering. The SPS glass-ceramic showed a bending strength, Weibull modulus, and toughness similar values to the cortical human bone. This material had a fatigue limit slightly superior to cortical bone and at least two times higher than commercial dental glass-ceramics and dentine. The in vitro studies indicate that soda-lime glass-ceramic is fully biocompatible. The in vivo studies in beagle jaws showed that implanted SPS rods presented no inflammatory changes in soft tissues surrounding implants in any of the 10 different cases after four months implantation. The radiological analysis indicates no signs of osseointegration lack around implants. Moreover, the biocide activity of SPS glass-ceramic versus Escherichia coli, was found to be >4log indicating that it prevents implant infections. Because of this, the SPS new glass-ceramic is particularly promising for dental applications (inlay, crowns, etc). Copyright © 2014 Elsevier Ltd. All rights reserved.

  6. Lead-Free Piezoelectric Ceramic Coatings Fabricated by Thermal Spray Process.

    Science.gov (United States)

    Yao, Kui; Chen, Shuting; Guo, Kun; Tan, Chee Kiang Ivan; Mirshekarloo, Meysam Sharifzadeh; Tay, Francis Eng Hock

    2017-11-01

    This paper starts from a review on the progress in fabrication of piezoelectric ceramic coatings by thermal spray method. For our experimental work, two types of lead-free piezoelectric ceramic coatings, including potassium-sodium niobate-based and bismuth sodium titanate-based, are fabricated by thermal spray process, and their structure, morphology, and piezoelectric properties are characterized. Our obtained lead-free ceramic coatings exhibit single phase of perovskite structure, relatively dense morphology, and competitive piezoelectric coefficients. The mechanism of forming the piezoelectric perovskite crystalline phase by thermal spray involving melting-recrystallization process is analyzed in comparison to that of ceramic synthesis through solid-state reaction. Suppression of volatile loss and decomposition at high temperature due to the extremely high melting and cooling rate in the thermal spray process, and the impact on the resulting structure are discussed. Significant advantages of the thermal spray method over alternative processing methods for forming piezoelectric ceramic coatings are summarized. The combination of environmentally friendly lead-free compositions and the scalable thermal spray processing method will promote more applications of piezoelectric ceramic coatings for producing distributive sensors and transducers, and forming advanced smart structures and systems.

  7. Incisal coverage or not in ceramic laminate veneers: A systematic review and meta-analysis.

    Science.gov (United States)

    Albanesi, Rafael Borges; Pigozzo, Mônica Nogueira; Sesma, Newton; Laganá, Dalva Cruz; Morimoto, Susana

    2016-09-01

    There is no consensus on whether incisal coverage is a risk or a protective factor in preparations for ceramic veneers. The aim of this systematic review and meta-analysis was to evaluate the survival rates of preparation designs for ceramic veneers with and without incisal coverage. Primary clinical studies with the following characteristics were included: 1) studies related to ceramic laminate veneers and 2) prospective or retrospective studies conducted in humans. From the selected studies, the survival rates and failures rates for ceramic veneers were extracted according to preparation design, with or without incisal coverage. The Cochran Q test and the I(2) statistic were used to evaluate heterogeneity. Metaregression, meta-analysis were performed. Two reviewers searched in the MEDLINE (Pubmed) and Cochrane Central Register of Controlled Trials (Central) electronic databases, from 1977 to June 5, 2016, without language restrictions. Eight studies out of 1145 articles initially identified were included for risk of bias and systematic assessment. No study was identified for crystalline ceramic veneers. The estimated survival rate for laminate veneers with incisal coverage was 88% and 91% for those without incisal coverage. Incisal coverage presented an OR of 1.25. Irrespective of the preparation designs, with or without incisal coverage, ceramic veneers showed high survival rates. As regard implications for future clinical research studies, randomized clinical studies are necessary to compare preparation designs with and without incisal coverage, and to provide clear descriptions of these preparation designs. Copyright © 2016 Elsevier Ltd. All rights reserved.

  8. Feasible Recycling of Industrial Waste Coal Gangue for Preparation of Mullite Based Ceramic Proppant

    Science.gov (United States)

    Li, Guomin; Ma, Haiqiang; Tian, Yuming; Wang, Kaiyue; Zhou, Yi; Wu, Yaqiao; Zou, Xinwei; Hao, Jianying; Bai, Pinbo

    2017-09-01

    Industrial waste coal gangue was successfully utilized to prepare the mullite-based ceramic proppants. The experiments involved the pelletizing technology of proppant through intensive mixer and following the sintering process under different temperatures. The crystalline phase, microstructure, density and breakage ratio of the proppants were investigated. The results showed that with the increasing of sintering temperature, the crystalline phases were transformed to rod-like mullite, which formed the cross-linked structure, improving the densification of proppants. Consequently, the breakage ratio under the closure pressure of 35 MPa exhibited declining trend and reached the minimum value of 6.8% at 1450 °C. Owing to the easy preparation, feasible design, low cost and moderate breakage ratio, the mullite-based ceramic proppant prepared by coal gangue and bauxite is promising candidate for fracturing proppants in future applications.

  9. Lightweight high performance ceramic material

    Science.gov (United States)

    Nunn, Stephen D [Knoxville, TN

    2008-09-02

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

  10. Ceramics in nuclear waste management

    Energy Technology Data Exchange (ETDEWEB)

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

    1979-05-01

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

  11. Micromolding for ceramic microneedle arrays

    NARCIS (Netherlands)

    van Nieuwkasteele-Bystrova, Svetlana Nikolajevna; Lüttge, Regina

    2011-01-01

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

  12. Science and Technology of Ceramics

    Indian Academy of Sciences (India)

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

  13. Science and Technology of Ceramics

    Indian Academy of Sciences (India)

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

  14. The application of positron annihilation lifetime spectroscopy to the study of glassy and partially crystalline materials

    Energy Technology Data Exchange (ETDEWEB)

    Zipper, M.D.; Hill, A.J. [Monash Univ., Clayton, VIC (Australia). Dept. of Materials Engineering

    1994-12-31

    The use of positron annihilation lifetime spectroscopy (PALS) as a materials characterisation technique is discussed and is illustrated by examples from the authors` laboratory. A brief guide to interpretation of PALS results for metals, semiconductors, ionic solids and molecular solids is presented; however, the paper focuses on recent results for glassy and partially crystalline ionic and molecular solids. Case studies are presented in which the phenomena studied by PALS include miscibility of polymer blends, plasticization of solid polymer electrolytes, crystallinity in molecular and ionic solids, nanostructure of glass-ceramics, and refractivity of fluoride glasses. Future directions for PALS research of the electronic and defect structures of materials are discussed. 140 refs., 1 tab., 19 figs.

  15. Crystalline silica in heated man-made vitreous fibres: a review.

    Science.gov (United States)

    Brown, Terry P; Harrison, Paul T C

    2014-02-01

    Refractory ceramic fibres (RCF) and alkaline earth silicate (AES) wools are types of man-made vitreous fibre (MMVF) that are used in demanding high-temperature industrial applications, generally above 900 °C and up to 1400 °C. When exposed to prolonged high temperatures, MMVF can devitrify with the formation of cristobalite and other crystalline silica species, which is of potential concern because crystalline silica (CS) is classified as carcinogenic. This article reviews the chemico-physical processes and morphological consequences of fibre devitrification, the forms and micro-location of CS produced, and the toxicity of devitrified fibres and the CS species formed in this way. It also examines scenarios for worker exposure to the products of fibre devitrification in industries using RCF and/or AES wools. We identify gaps in knowledge and make recommendations for future research. Copyright © 2013 Elsevier Inc. All rights reserved.

  16. Crystalline structures of poly(L-lactide) formed under pressure and structure transitions with heating

    DEFF Research Database (Denmark)

    Huang, Shaoyong; Li, Hongfei; Yu, Donghong

    2013-01-01

    ), real time synchrotron small-angle X-ray scattering (SR-SAXS) and differential scanning calorimetry (DSC) during this process. The structural parameters, such as the size of crystallites, the inverse spacing, the long periods and lamellae thicknesses decrease with pressure increasing. Based...... on the peculiarities of crystalline structure and crystallization behaviors, low and high pressure regions were revealed: disordered α crystal was formed in the high pressure region (>1 kbar). A layer located intermediate between crystalline and melt-like regions was observed, which finally took on crystalline order......The isothermally crystallized poly(L-lactide) (PLLA) samples were obtained at 135 °C under pressures (Pc) ranging from 1 bar to 2.5 kbar. The crystalline structures, the structure transition, and thermal properties of the prepared samples were investigated by wide-angle X-ray diffraction (WAXD...

  17. Gas turbine ceramic-coated-vane concept with convection-cooled porous metal core

    Science.gov (United States)

    Kascak, A. F.; Liebert, C. H.; Handschuh, R. F.; Ludwig, L. P.

    1981-01-01

    Analysis and flow experiments on a ceramic-coated-porous-metal vane concept indicated the feasibility, from a heat transfer standpoint, of operating in a high-temperature (2500 F) gas turbine cascade facility. The heat transfer and pressure drop calculations provided a basis for selecting the ceramic layer thickness (to 0.08 in.), which was found to be the dominant factor in the overall heat transfer coefficient. Also an approximate analysis of the heat transfer in the vane trailing edge revealed that with trailing-edge ejection the ceramic thickness could be reduced to (0.01 in.) in this portion of the vane.

  18. Low thermal expansion glass ceramics

    CERN Document Server

    1995-01-01

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

  19. Ceramic membrane development in NGK

    Science.gov (United States)

    Araki, Kiyoshi; Sakai, Hitoshi

    2011-05-01

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

  20. Detoxification and immobilization of chromite ore processing residue in spinel-based glass-ceramic

    Energy Technology Data Exchange (ETDEWEB)

    Liao, Chang-Zhong [Guangdong Key Laboratory of Agricultural Environment Pollution Integrated Control, Guangdong Institute of Eco-Environmental and Soil Sciences, Guangzhou 510650 (China); Department of Civil Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong Special Administrative Region (China); Tang, Yuanyuan [School of Environmental Science and Engineering, South University of Science and Technology of China, Shenzhen 518055 (China); Lee, Po-Heng [Department of Civil & Environmental Engineering, The Hong Kong Polytechnic University, Hong Kong Special Administrative Region (China); Liu, Chengshuai, E-mail: csliu@soil.gd.cn [Guangdong Key Laboratory of Agricultural Environment Pollution Integrated Control, Guangdong Institute of Eco-Environmental and Soil Sciences, Guangzhou 510650 (China); State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550009 (China); Shih, Kaimin, E-mail: kshih@hku.hk [Department of Civil Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong Special Administrative Region (China); Li, Fangbai [Guangdong Key Laboratory of Agricultural Environment Pollution Integrated Control, Guangdong Institute of Eco-Environmental and Soil Sciences, Guangzhou 510650 (China)

    2017-01-05

    Graphical abstract: Schematic illustration of detoxification and immobilization of chromite ore processing residue in spinel-based glass-ceramic matrix. All Cr(VI) species is reduced to Cr(III) and most chromium contents are incorporated into spinel structure where the residual chromium are resided in the glass networks. - Highlights: • COPR was detoxified and immobilized in a spinel-based glass-ceramic matrix. • Cr-rich crystalline phase was determined to be MgCr{sub 1.32}Fe{sub 0.19}Al{sub 0.49}O{sub 4} spinel. • The partitioning ratio of Cr into spinel in the glass-ceramic can be up to 77%. • No Cr(VI) was observed after conversion of COPR into a glass-ceramic. • TCLP results demonstrate the superiority of the final product in immobilizing Cr. - Abstract: A promising strategy for the detoxification and immobilization of chromite ore processing residue (COPR) in a spinel-based glass-ceramic matrix is reported in this study. In the search for a more chemically durable matrix for COPR, the most critical crystalline phase for Cr immobilization was found to be a spinel solid solution with a chemical composition of MgCr{sub 1.32}Fe{sub 0.19}Al{sub 0.49}O{sub 4}. Using Rietveld quantitative X-ray diffraction analysis, we identified this final product is with the phases of spinel (3.5 wt.%), diopside (5.2 wt.%), and some amorphous contents (91.2 wt.%). The partitioning ratio of Cr reveals that about 77% of the Cr was incorporated into the more chemically durable spinel phase. The results of Cr K-edge X-ray absorption near-edge spectroscopy show that no Cr(VI) was observed after conversion of COPR into a glass-ceramic, which indicates successful detoxification of Cr(VI) into Cr(III) in the COPR-incorporated glass-ceramic. The leaching performances of Cr{sub 2}O{sub 3} and COPR-incorporated glass-ceramic were compared with a prolonged acid-leaching test, and the results demonstrate the superiority of the COPR-incorporated glass-ceramic matrix in the

  1. Corrosion protection of SiC-based ceramics with CVD mullite coatings

    Energy Technology Data Exchange (ETDEWEB)

    Auger, M.L.; Sarin, V.K. [Boston Univ., MA (United States). Dept. of Mfg. Engineering

    1997-12-01

    For the first time, crystalline mullite coatings have been chemically vapor deposited on SiC substrates to enhance its corrosion and oxidation resistance. Thermodynamic and kinetic considerations have been utilized to produce mullite coatings with a variety of growth rates, compositions, and morphologies. The flexibility of processing can be exploited to produce coated ceramics with properties tailored to specific applications and varied corrosive environments.

  2. Crystalline deposits in the macula - tamoxifen maculopathy or macular telangiectasia?

    Science.gov (United States)

    Rijal, Roshija Khanal; Nakhwa, Chinmay; Sindal, Manavi D

    2014-01-01

    Tamoxifen citrate is an anti-estrogen agent used in the treatment of breast carcinoma. Crystalline maculopathy is a rare complication of tamoxifen therapy. The clinical picture resembles that of idiopathic macular telangiectasia (IMT) Type 2, which is a more common clinical entity. To report a case of crystalline maculopathy secondary to tamoxifen and highlight the importance of the medical history and investigations in differentiating it from IMT Type 2. A diabetic female with a past history of breast carcinoma treated with tamoxifen came to the hospital for a routine eye check-up. Crystalline deposits were seen in the parafoveal region in both the eyes.The spectral domain optical coherence tomography (SD-OCT) showed foveal cysts in the inner retinal layer and fundus autofluorescence (FAF) and fundus fluorescein angiography (FFA) were within normal limits. While tamoxifen maculopathy is reversible on stopping the therapy, IMT needs a long-term follow-up to monitor the potential risk of loss of vision due to choroidal neovascularization, hence necessitating the distinction between these two different clinical entities.

  3. Heterogeneous ice nucleation controlled by the coupling of surface crystallinity and surface hydrophilicity

    CERN Document Server

    Bi, Yuanfei; Li, Tianshu

    2015-01-01

    The microscopic mechanisms controlling heterogeneous ice nucleation are complex and remain poorly understood. Although good ice nucleators are generally believed to match ice lattice and to bind water, counter examples are often identified. Here we show, by advanced molecular simulations, that the heterogeneous nucleation of ice on graphitic surface is controlled by the coupling of surface crystallinity and surface hydrophilicity. Molecular level analysis reveals that the crystalline graphitic lattice with an appropriate hydrophilicity may indeed template ice basal plane by forming a strained ice layer, thus significantly enhancing its ice nucleation efficiency. Remarkably, the templating effect is found to transit from within the first contact layer of water to the second as the hydrophilicity increases, yielding an oscillating distinction between the crystalline and amorphous graphitic surfaces in their ice nucleation efficiencies. Our study sheds new light on the long-standing question of what constitutes ...

  4. Effect of Microstructure on Reliability of Ca(TiZr)O3-Based Multilayer Ceramic Capacitors

    Science.gov (United States)

    Motoki, Tomoo; Naito, Masahiro; Sano, Harunobu; Konoike, Takehiro; Tomono, Kunisaburo

    2000-09-01

    We examined the reliability of Ca(TiZr)O3 (CTZ)-based Ni-electrode multilayer ceramic capacitors (MLCs) prepared by two different processes with particular interest in the microstructure. One process was to calcine the mixture of CaCO3 and TiO2 to prepare CaTiO3 (CT) powder and the mixture of CaCO3 and ZrO2 to prepare CaZrO3 (CZ) powder, and then mix these calcined powders and sinter them to synthesize the CTZ-based ceramics. The other was to calcine the mixture of CaCO3, TiO2 and ZrO2 powders together to prepare CTZ powder and then sinter them. These two processes of CTZ ceramic preparation resulted in a different crystallinity and distribution of the elements. We found that these factors influenced the reliability of CTZ-based MLCs.

  5. Bone bonding ability of some borate bio-glasses and their corresponding glass-ceramic derivatives

    Directory of Open Access Journals (Sweden)

    Fatma H. Margha

    2012-12-01

    Full Text Available Ternary borate glasses from the system Na2O·CaO·B2O3 together with soda-lime-borate samples containing 5 wt.% of MgO, Al2O3, SiO2 or P2O5 were prepared. The obtained glasses were converted to their glass-ceramic derivatives by controlled heat treatment. X-ray diffraction was employed to investigate the separated crystalline phases in glass-ceramics after heat treatment of the glassy samples. The glasses and corresponding glass-ceramics after immersion in water or diluted phosphate solution for extended times were characterized by the grain method (adopted by several authors and recommended by ASTM and Fourier-transform infrared spectra to justify the formation of hydroxyapatite as an indication of the bone bonding ability. The influence of glass composition on bioactivity potential was discussed too.

  6. Investigation of zircon/zirconia ceramics doped with {sup 239}Pu and {sup 238}Pu

    Energy Technology Data Exchange (ETDEWEB)

    Burakov, B.E.; Anderson, E.B.; Zamoryanskaya, M.V.; Nikolaeva, E.V.; Strykanova, E.E.; Yagovkina, M.A. [V.G. Khlopin Radium Institute, Saint Petersburg (Russian Federation)

    2001-07-01

    Several samples of crystalline double-phase ceramics based on zircon, (Zr,Pu)SiO{sub 4} and zirconia, (Zr,Pu)O{sub 2}, were synthesized by sintering in air, precursors containing approximately 5-6 and 10 wt% {sup 239}Pu, respectively. One sample doped with 5-6 wt% {sup 238-39-40}Pu was also obtained under the same conditions. All ceramic samples were studied by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), electron probe microanalysis (EPMA) and MCC-1 leach test in deionized water at 90 C. Results indicate that even radiation damaged zircon/zirconia ceramics retain high chemical resistance and mechanical durability. (author)

  7. Optical method and apparatus for detection of defects and microstructural changes in ceramics and ceramic coatings

    Science.gov (United States)

    Ellingson, William A.; Todd, Judith A.; Sun, Jiangang

    2001-01-01

    Apparatus detects defects and microstructural changes in hard translucent materials such as ceramic bulk compositions and ceramic coatings such as after use under load conditions. The beam from a tunable laser is directed onto the sample under study and light reflected by the sample is directed to two detectors, with light scattered with a small scatter angle directed to a first detector and light scattered with a larger scatter angle directed to a second detector for monitoring the scattering surface. The sum and ratio of the two detector outputs respectively provide a gray-scale, or "sum" image, and an indication of the lateral spread of the subsurface scatter, or "ratio" image. This two detector system allows for very high speed crack detection for on-line, real-time inspection of damage in ceramic components. Statistical image processing using a digital image processing approach allows for the quantative discrimination of the presence and distribution of small flaws in a sample while improving detection reliability. The tunable laser allows for the penetration of the sample to detect defects from the sample's surface to the laser's maximum depth of penetration. A layered optical fiber directs the incoming laser beam to the sample and transmits each scattered signal to a respective one of the two detectors.

  8. Processing and enhanced piezoelectric properties of highly oriented compositionally modified Pb(Zr,Ti)O3 ceramics fabricated by magnetic alignment

    Science.gov (United States)

    Miwa, Yasunari; Kawada, Shinichiro; Kimura, Masahiko; Omiya, Suetake; Kubodera, Noriyuki; Ando, Akira; Suzuki, Tohru S.; Uchikoshi, Tetsuo; Sakka, Yoshio

    2015-04-01

    Highly oriented compositionally modified Pb(Zr,Ti)O3 (PZT) ceramics were successfully obtained by slip casting in a high magnetic field. PZT is a well-known superior ceramic with the highest piezoelectric properties, and these properties have been expected to be further improved through crystalline orientation. However, highly oriented PZT ceramics fabricated by slip casting in a high magnetic field have never been reported. We obtained oriented ceramics using compositionally modified PZT with Pb(Ni,Nb)O3, and their Lotgering factor was 0.77. The electromechanical coupling coefficient (k31) increased by 30%, and an extremely high value of 0.44 was achieved for the oriented ceramics.

  9. OXYGEN TRANSPORT CERAMIC MEMBRANES

    Energy Technology Data Exchange (ETDEWEB)

    Dr. Sukumar Bandopadhyay; Dr. Nagendra Nagabhushana

    2003-01-01

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

  10. Occupational exposure to crystalline silica at Alberta work sites.

    Science.gov (United States)

    Radnoff, Diane; Todor, Maria S; Beach, Jeremy

    2014-01-01

    Although crystalline silica has been recognized as a health hazard for many years, it is still encountered in many work environments. Numerous studies have revealed an association between exposure to respirable crystalline silica and the development of silicosis and other lung diseases including lung cancer. Alberta Jobs, Skills, Training and Labour conducted a project to evaluate exposure to crystalline silica at a total of 40 work sites across 13 industries. Total airborne respirable dust and respirable crystalline silica concentrations were quite variable, but there was a potential to exceed the Alberta Occupational Exposure Limit (OEL) of 0.025 mg/m(3) for respirable crystalline silica at many of the work sites evaluated. The industries with the highest potentials for overexposure occurred in sand and mineral processing (GM 0.090 mg/m(3)), followed by new commercial building construction (GM 0.055 mg/m(3)), aggregate mining and crushing (GM 0.048 mg/m(3)), abrasive blasting (GM 0.027 mg/m(3)), and demolition (GM 0.027 mg/m(3)). For worker occupations, geometric mean exposure ranged from 0.105 mg/m(3) (brick layer/mason/concrete cutting) to 0.008 mg/m(3) (dispatcher/shipping, administration). Potential for GM exposure exceeding the OEL was identified in a number of occupations where it was not expected, such as electricians, carpenters and painters. These exposures were generally related to the specific task the worker was doing, or arose from incidental exposure from other activities at the work site. The results indicate that where there is a potential for activities producing airborne respirable crystalline silica, it is critical that the employer include all worker occupations at the work site in their hazard assessment. There appears to be a relationship between airborne total respirable dust concentration and total respirable dust concentrations, but further study is require to fully characterize this relationship. If this relationship holds true

  11. Chemical treatment and biomimetic coating evaluating in zirconia-alumina ceramics; Avaliacao de tratamentos quimicos e recobrimento biomimetico em ceramicas de alumina-zirconia

    Energy Technology Data Exchange (ETDEWEB)

    Aguiar, Amanda Abati

    2007-07-01

    Ceramic materials, as alumina and zirconia have been explored along the years as biomaterials application. The bio inert nature has been stimulating the development of new alternatives, as chemical treatments to improve the biological application of these ceramics. The biomimetic process of bio inert ceramics for coating apatite is based on soaking the implant in a simulated body fluid, SBF, with ion concentrations nearly equal to those of human blood plasma. The bioactivity of the material is related with the formation of a layer constituted of hydroxyapatite low crystalline, similar to the biological apatite. The biocompatibility associated to the structural properties of the alumina and zirconia has been stimulating the clinical use of these materials, mainly in areas of larger mechanical requests, places not recommended for bioactive hydroxyapatite, for instance. In this work samples of alumina, zirconia doped with Yttria (3% mol) and composites of alumina and zirconia doped with Yttria (3% mol) were prepared by co-precipitation method, calcinate, sintered, chemically treated with solutions of acid phosphoric and sodium hydroxide and them immersed in 1.0 M and 1.5 M SBF. The calcinate powders were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), gas adsorption (BET) and laser diffraction. The XRD results indicate that the samples are low crystalline. It was observed for BET that the samples present high specific surface area. The results of laser diffraction and SEM showed that the powders are agglomerates. The sintered samples were analyzed by XRD, SEM and X-ray fluorescence (XRF). The phases quantified by Rietveld method were: cubic, tetragonal and monoclinic of the zirconia, besides the phase alpha of the alumina. The chemical treatment with phosphoric acid didn't present a tendency of larger apatite formation in relation to the samples no chemically treated. The treatment with sodium hydroxide provoked accentuated transformation

  12. SUPPORTED DENSE CERAMIC MEMBRANES FOR OXYGEN SEPARATION

    Energy Technology Data Exchange (ETDEWEB)

    Timothy L. Ward

    2002-07-01

    Mixed-conducting ceramics have the ability to conduct oxygen with perfect selectivity at elevated temperatures, making them extremely attractive as membrane materials for oxygen separation and membrane reactor applications. While the conductivity of these materials can be quite high at elevated temperatures (typically 800-1000 C), much higher oxygen fluxes, or, alternatively, equivalent fluxes at lower temperatures, could be provided by supported thin or thick film membrane layers. Based on that motivation, the objective of this project was to explore the use of ultrafine aerosol-derived powder of a mixed-conducting ceramic material for fabrication of supported thick-film dense membranes. The project focused on the mixed-conducting ceramic composition SrCo{sub 0.5}FeO{sub x} (SCFO) because of the desirable permeability and stability of that material, as reported in the literature. Appropriate conditions to produce the submicron SrCo{sub 0.5}FeO{sub x} powder using aerosol pyrolysis were determined. Porous supports of the same composition were produced by partial sintering of a commercially obtained powder that possessed significantly larger particle size than the aerosol-derived powder. The effects of sintering conditions (temperature, atmosphere) on the porosity and microstructure of the porous discs were studied, and a standard support fabrication procedure was adopted. Subsequently, a variety of paste and slurry formulations were explored utilizing the aerosol-derived SCFO powder. These formulations were applied to the porous SCFO support by a doctor blade or spin coating procedure. Sintering of the supported membrane layer was then conducted, and additional layers were deposited and sintered in some cases. The primary characterization methods were X-ray diffraction and scanning electron microscopy, and room-temperature nitrogen permeation was used to assess defect status of the membranes.We found that non-aqueous paste/slurry formulations incorporating

  13. Microstructure and properties of LZSA glass-ceramic foams

    Energy Technology Data Exchange (ETDEWEB)

    Sousa, E. de [Graduate Program on Materials Science and Engineering-PGMAT, Federal University of Santa Catarina-UFSC, P.O. Box 476, 88040-900 Florianopolis, SC (Brazil); Rambo, C.R. [Graduate Program on Materials Science and Engineering-PGMAT, Federal University of Santa Catarina-UFSC, P.O. Box 476, 88040-900 Florianopolis, SC (Brazil); Department of Chemical Engineering-EQA, Federal University of Santa Catarina-UFSC, P.O. Box 476, 88040-900 Florianopolis, SC (Brazil)], E-mail: Rambo@enq.ufsc.br; Hotza, D. [Graduate Program on Materials Science and Engineering-PGMAT, Federal University of Santa Catarina-UFSC, P.O. Box 476, 88040-900 Florianopolis, SC (Brazil); Department of Chemical Engineering-EQA, Federal University of Santa Catarina-UFSC, P.O. Box 476, 88040-900 Florianopolis, SC (Brazil); Oliveira, A.P. Novaes de [Graduate Program on Materials Science and Engineering-PGMAT, Federal University of Santa Catarina-UFSC, P.O. Box 476, 88040-900 Florianopolis, SC (Brazil); Department of Mechanical Engineering-EMC, Federal University of Santa Catarina-UFSC, P.O. Box 476, 88040-900 Florianopolis, SC (Brazil); Fey, T.; Greil, P. [Department of Materials Science, Glass and Ceramics, University of Erlangen-Nuremberg, Martensstrasse 5, D-91058 Erlangen (Germany)

    2008-03-15

    Commercial polyurethane foams with a monomodal pore size distribution were used to produce LZSA glass-ceramic foams by the polymeric sponge method. A suspension containing LZSA glass powder, bentonite and sodium silicate was prepared in isopropanol to impregnate the polymeric foams by dip coating. The sintering conditions were varied in the range of 700-850 deg. C for 30-180 min. The cellular microstructure of glass-ceramic foams was characterized by scanning electron microscopy (SEM) and micro-computer X-ray tomography ({mu}CT). Optimum physical, mechanical and fluidynamic properties of the LZSA glass-ceramic foams were obtained at 750 deg. C for 60 min. Main crystalline phases detected were {beta}-spodumene and zirconium silicate. The compressive strength of the foams (0.1-10 MPa) is strongly dependent on their overall porosity and their behaviour could be explained using the Gibson-Ashby model. The Darcyan permeability of LZSA foams was found to be in the range of 0.1-4 x 10{sup -9} m{sup 2}, which is in the order of magnitude of cellular supports for aerosol filters, and, therefore, suitable for several other technological applications.

  14. 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.

  15. Quantitative firing transformations of a triaxial ceramic by X-ray diffraction methods

    Directory of Open Access Journals (Sweden)

    M. S. Conconi

    2014-12-01

    Full Text Available The firing transformations of traditional (clay based ceramics are of technological and archeological interest, and are usually reported qualitatively or semiquantitatively. These kinds of systems present an important complexity, especially for X-ray diffraction techniques, due to the presence of fully crystalline, low crystalline and amorphous phases. In this article we present the results of a qualitative and quantitative X-ray diffraction Rietveld analysis of the fully crystalline (kaolinite, quartz, cristobalite, feldspars and/or mullite, the low crystalline (metakaolinite and/or spinel type pre-mullite and glassy phases evolution of a triaxial (clay-quartz-feldspar ceramic fired in a wide temperature range between 900 and 1300 ºC. The employed methodology to determine low crystalline and glassy phase abundances is based in a combination of the internal standard method and the use of a nanocrystalline model where the long-range order is lost, respectively. A preliminary sintering characterization was carried out by contraction, density and porosity evolution with the firing temperature. Simultaneous thermo-gravimetric and differential thermal analysis was carried out to elucidate the actual temperature at which the chemical changes occur. Finally, the quantitative analysis based on the Rietveld refinement of the X-ray diffraction patterns was performed. The kaolinite decomposition into metakaolinite was determined quantitatively; the intermediate (980 ºC spinel type alumino-silicate formation was also quantified; the incongruent fusion of the potash feldspar was observed and quantified together with the final mullitization and the amorphous (glassy phase formation.The methodology used to analyze the X-ray diffraction patterns proved to be suitable to evaluate quantitatively the thermal transformations that occur in a complex system like the triaxial ceramics. The evaluated phases can be easily correlated with the processing variables and

  16. Quantitative firing transformations of a triaxial ceramic by X-ray diffraction methods

    Energy Technology Data Exchange (ETDEWEB)

    Conconi, M.S.; Gauna, M.R.; Serra, M.F. [Centro de Tecnologia de Recursos Minerales y Ceramica (CETMIC), Buenos Aires (Argentina); Suarez, G.; Aglietti, E.F.; Rendtorff, N.M., E-mail: rendtorff@cetmic.unlp.edu.ar [Universidad Nacional de La Plata (UNLP), Buenos Aires (Argentina). Fac. de Ciencias Exactas. Dept. de Quimica

    2014-10-15

    The firing transformations of traditional (clay based) ceramics are of technological and archaeological interest, and are usually reported qualitatively or semi quantitatively. These kinds of systems present an important complexity, especially for X-ray diffraction techniques, due to the presence of fully crystalline, low crystalline and amorphous phases. In this article we present the results of a qualitative and quantitative X-ray diffraction Rietveld analysis of the fully crystalline (kaolinite, quartz, cristobalite, feldspars and/or mullite), the low crystalline (metakaolinite and/or spinel type pre-mullite) and glassy phases evolution of a triaxial (clay-quartz-feldspar) ceramic fired in a wide temperature range between 900 and 1300 deg C. The employed methodology to determine low crystalline and glassy phase abundances is based in a combination of the internal standard method and the use of a nanocrystalline model where the long-range order is lost, respectively. A preliminary sintering characterization was carried out by contraction, density and porosity evolution with the firing temperature. Simultaneous thermo-gravimetric and differential thermal analysis was carried out to elucidate the actual temperature at which the chemical changes occur. Finally, the quantitative analysis based on the Rietveld refinement of the X-ray diffraction patterns was performed. The kaolinite decomposition into metakaolinite was determined quantitatively; the intermediate (980 deg C) spinel type alumino-silicate formation was also quantified; the incongruent fusion of the potash feldspar was observed and quantified together with the final mullitization and the amorphous (glassy) phase formation.The methodology used to analyze the X-ray diffraction patterns proved to be suitable to evaluate quantitatively the thermal transformations that occur in a complex system like the triaxial ceramics. The evaluated phases can be easily correlated with the processing variables and materials

  17. Microstructure and spectroscopic investigations of calcium zinc bismuth phosphate glass ceramics doped with manganese ions

    Science.gov (United States)

    Suneel Kumar, A.; Sambasiva Rao, M. V.; Chinna Ram, G.; Krishna Rao, D.

    2017-07-01

    Multi-component 10CaF2-20ZnO-(15 - x)Bi2O3-55P2O5:xMnO (0 ≤ x ≤ 2.5) glass ceramics were synthesised by melt quenching technique and heat treatment. The prepared glass ceramics were characterised by XRD, DTA, EDS and SEM. Spectroscopic studies such as optical absorption, EPR, FTIR and Raman were also carried out on these glass ceramics. The XRD and SEM studies have indicated that ceramic samples contain well defined and randomly distributed grains of different crystalline phases. The observed increase of enthalpy from DTA patterns up to 1 mol% of MnO indicates that the crystallisation starts initially from the surface of the material then gradually it is extended to the volume of the material and this influence is meagre at higher concentrations of MnO. The absorption spectra of manganese doped glass ceramics have exhibited two types of conventional bands; one due to Mn2+ ions and other due to Mn3+ ions. The EPR spectra of MnO doped glass ceramics showed a resonance signal around g2 = 2.023 with a six line hyperfine structure and another signal at about g1 = 4.314. The relative intensity and half-width of these two signals are observed to increase with the increase in the concentration of manganese ions up to 1 mol% beyond this concentration it is found to decrease. Such observation indicates the conversion of part of Mn2+ ions into Mn3+ ions in the glass ceramic matrix. The observed increase in the intensity of symmetrical structural units at the expense of asymmetrical structural units from the FTIR and Raman spectra at higher concentration of MnO indicating that Mn2+ ions occupy the network forming positions in the glass ceramic structure.

  18. Improved ceramic slip casting technique. [application to aircraft model fabrication

    Science.gov (United States)

    Buck, Gregory M. (Inventor); Vasquez, Peter (Inventor)

    1993-01-01

    A primary concern in modern fluid dynamics research is the experimental verification of computational aerothermodynamic codes. This research requires high precision and detail in the test model employed. Ceramic materials are used for these models because of their low heat conductivity and their survivability at high temperatures. To fabricate such models, slip casting techniques were developed to provide net-form, precision casting capability for high-purity ceramic materials in aqueous solutions. In previous slip casting techniques, block, or flask molds made of plaster-of-paris were used to draw liquid from the slip material. Upon setting, parts were removed from the flask mold and cured in a kiln at high temperatures. Casting detail was usually limited with this technique -- detailed parts were frequently damaged upon separation from the flask mold, as the molded parts are extremely delicate in the uncured state, and the flask mold is inflexible. Ceramic surfaces were also marred by 'parting lines' caused by mold separation. This adversely affected the aerodynamic surface quality of the model as well. (Parting lines are invariably necessary on or near the leading edges of wings, nosetips, and fins for mold separation. These areas are also critical for flow boundary layer control.) Parting agents used in the casting process also affected surface quality. These agents eventually soaked into the mold, the model, or flaked off when releasing the case model. Different materials were tried, such as oils, paraffin, and even an algae. The algae released best, but some of it remained on the model and imparted an uneven texture and discoloration on the model surface when cured. According to the present invention, a wax pattern for a shell mold is provided, and an aqueous mixture of a calcium sulfate-bonded investment material is applied as a coating to the wax pattern. The coated wax pattern is then dried, followed by curing to vaporize the wax pattern and leave a shell

  19. Real-time TEM imaging of the formation of crystalline nanoscale gaps.

    Science.gov (United States)

    Strachan, Douglas R; Johnston, Danvers E; Guiton, Beth S; Datta, Sujit S; Davies, Peter K; Bonnell, Dawn A; Johnson, A T Charlie

    2008-02-08

    We present real-time transmission electron microscopy of nanogap formation by feedback controlled electromigration that reveals a remarkable degree of crystalline order. Crystal facets appear during feedback controlled electromigration indicating a layer-by-layer, highly reproducible electromigration process avoiding thermal runaway and melting. These measurements provide insight into the electromigration induced failure mechanism in sub-20 nm size interconnects, indicating that the current density at failure increases as the width decreases to approximately 1 nm.

  20. Real-Time TEM Imaging of the Formation of Crystalline Nanoscale Gaps

    Science.gov (United States)

    Strachan, Douglas R.; Johnston, Danvers E.; Guiton, Beth S.; Datta, Sujit S.; Davies, Peter K.; Bonnell, Dawn A.; Johnson, A. T. Charlie

    2008-02-01

    We present real-time transmission electron microscopy of nanogap formation by feedback controlled electromigration that reveals a remarkable degree of crystalline order. Crystal facets appear during feedback controlled electromigration indicating a layer-by-layer, highly reproducible electromigration process avoiding thermal runaway and melting. These measurements provide insight into the electromigration induced failure mechanism in sub-20 nm size interconnects, indicating that the current density at failure increases as the width decreases to approximately 1 nm.

  1. Inorganic glasses and glass-ceramics studied by isothermal mechanical spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Riviere, A. [Laboratoire de Mecanique et Physique des Materiaux, UMR CNRS 6617, ENSMA, BP 40109, 86961 Futuroscope (France)]. E-mail: andre.riviere@lmpm.ensma.fr; Chocinski-Arnault, L. [Laboratoire de Mecanique et Physique des Materiaux, UMR CNRS 6617, ENSMA, BP 40109, 86961 Futuroscope (France)

    2006-12-20

    This paper describes isothermal mechanical spectroscopy measurements carried out in silicate glasses and LAS (Li{sub 2}O-Al{sub 2}O{sub 3}-SiO{sub 2})-type glass-ceramics. Single alkali silicate glass Na{sub 2}O.3SiO{sub 2} exhibits two relaxation peaks. The first one located at a low temperature is generally assigned to the stress-induced diffusion of alkali ions. The second relaxation peak is attributed to the 'non-bridging oxygen'. Mixed alkali silicate glasses (1 - x)Na{sub 2}O.xLi{sub 2}O.3SiO{sub 2} with x = 0, 0.25, 0.5, 0.75 exhibit the mixed alkali peak. And also the 'non-bridging oxygen' peak. Two LAS-type glass-ceramics having the same chemical composition but different microstructures: '{beta}-quartz' and '{beta}-spodumene' type, respectively, and their parent glass have been studied. For the glass which does not contain 'non-bridging oxygen', a single mechanical relaxation peak linked with the stress-induced movement of lithium ions is observed. On the contrary, two peaks occur in the '{beta}-quartz' and '{beta}-spodumene' glass-ceramics. The 'low-temperature' peak ({approx}340 K for 1 Hz) is linked with ion mobility in the respective main crystalline phase. The origin of the 'high-temperature' peak is totally different for the two glass-ceramics; in the '{beta}-quartz' glass-ceramic, it is due to Mg{sup 2+} and Zn{sup 2+} ion relaxation in the crystalline phase, whereas in the '{beta}-spodumene' glass-ceramic, it is linked with a complex entity within the residual vitreous phase.

  2. Phosphorus-doped Amorphous Silicon Nitride Films Applied to Crystalline Silicon Solar Cells

    NARCIS (Netherlands)

    Feinäugle, Matthias

    2008-01-01

    The Photovoltaics Group at the Universitat Politècnica de Catalunya is investigating silicon carbide (SiC) for the electronic passivation of the surface of crystalline silicon solar cells. The doping of SiC passivation layers with phosphorus resulted in a clear improvement of the minority carrier

  3. A paint removal concept with side-chain liquid crystalline polymers as primer material

    NARCIS (Netherlands)

    Wielen, van der M.W.J.; Cohen Stuart, M.A.; Fleer, G.J.; Nieuwhof, R.P.; Marcelis, A.T.M.; Sudhölter, E.J.R.

    2001-01-01

    A new paint removal concept is introduced making use of a polymer primer layer with a sharp softening temperature. For this, a new class of side-chain liquid crystalline polymers with polar moieties in the backbone has been developed and studied in thin films. These polymers form lamellar-ordered

  4. Effect of organoclay on the orientation and thermal properties of liquid-crystalline polymers

    CSIR Research Space (South Africa)

    Bandyopadhyay, J

    2007-08-01

    Full Text Available in the pure LCP; in the nanocomposites, the polymer chains tended to orient in the direction of the dispersed clay layers. According to the DSC results, during first heating, the first melting peak represents the crystalline to nematic transition and, after...

  5. Fabricating with crystalline Si to improve superconducting detector performance

    Science.gov (United States)

    Beyer, A. D.; Hollister, M. I.; Sayers, J.; Frez, C. F.; Day, P. K.; Golwala, S. R.

    2017-05-01

    We built and measured radio-frequency (RF) loss tangent, tan δ, evaluation structures using float-zone quality silicon-on-insulator (SOI) wafers with 5 μm thick device layers. Superconducting Nb components were fabricated on both sides of the SOI Si device layer. Our main goals were to develop a robust fabrication for using crystalline Si (c-Si) dielectric layers with superconducting Nb components in a wafer bonding process and to confirm that tan δ with c-Si dielectric layers was reduced at RF frequencies compared to devices fabricated with amorphous dielectrics, such as SiO2 and SixNy, where tan δ ∼ 10-3. Our primary test structure used a Nb coplanar waveguide (CPW) readout structure capacitively coupled to LC resonators, where the capacitors were defined as parallel-plate capacitors on both sides of a c-Si device layer using a wafer bonding process with benzocyclobutene (BCB) wafer bonding adhesive. Our control experiment, to determine the intrinsic tan δ in the SOI device layer without wafer bonding, also used Nb CPW readout coupled to LC resonators; however, the parallel-plate capacitors were fabricated on both sides of the Si device layer using a deep reactive ion etch (DRIE) to access the c-Si underside through the buried oxide and handle Si layers in the SOI wafers. We found that our wafer bonded devices demonstrated F· δ = (8 ± 2) × 10-5, where F is the filling fraction of two-level states (TLS). For the control experiment, F· δ = (2.0 ± 0.6) × 10-5, and we discuss what may be degrading the performance in the wafer bonded devices as compared to the control devices.

  6. Characterisation of Ti-6Al-4V/glass-ceramic and pre-oxidised Kovar/glass-ceramic interfaces

    Science.gov (United States)

    Yates, Paul

    Glass-to-metal seals are used in a wide range of components. The nature of the interfaces between the constituents is often crucial to the performance of the seal and thus the aim of this study was to characterise the various interfaces in a novel seal made from a strontium boroaluminate glass-ceramic and the alloys Ti-6Al-4V and Kovar (Fe-29Ni-17Co). A titanium boride was found, by STEM, EELS and WDX, to have formed at the glass-ceramic to Ti-6Al-4V interface and to be bonded to both the metal on one side and the glass-ceramic on the other, in contrast to the classic view of glass to metal interfaces where bonding is thought to be promoted through metal dissolving into the glass / glass-ceramic. To establish bonding at the other interface, it was necessary to grow an oxide layer on the Kovar, by heating in air at 700 °C or 800 °C for 10 minutes. The oxide grown at both temperatures was shown (by XPS, XRD, SEM, EDX, STEM and Raman) to have the same composition, with the only significant difference being thickness (2.1 +/- 0.6) µm and (4.0 +/- 0.2) µm thick, for the oxides grown at 700 °C and 800 °C respectively. However, the oxide was found to be much more complex than was indicated by prior literature, comprising four layers. The top layer of the oxide was (Fe,Co)_3O_4, with an Fe_2O_3 layer beneath it. Below these layers were a further two layers of (Fe,Co,Ni)_3O_4. When heated to 800 °C, to simulate the sealing conditions, the oxide was changed to an Fe_3O_4 layer with metallic cobalt and nickel inclusions. Bonding was shown, by SEM and STEM, to occur between the oxidised Kovar and the glass-ceramic, as a result of dissolution of iron from the oxide into the glass. Although the interfaces were not definitively optimised, the seals produced were satisfactory and hermetic.

  7. Internal fit of two all-ceramic systems and metal-ceramic crowns

    Directory of Open Access Journals (Sweden)

    Leandro Moura Martins

    2012-04-01

    Full Text Available OBJECTIVES: The aim of this study was to investigate the internal fit (IF of glass-infiltrated alumina (ICA - In-Ceram Alumina, yttria-stabilized tetragonal zirconia polycrystals (Y-TZP - IPS e.max ZirCAD, and metal-ceramic (MC - Ni-Cr alloy crowns. MATERIAL AND METHODS: Sixty standardized resin-tooth replicas of a maxillary first molar were produced for crown placement and divided into 3 groups (n=20 each according to the core material used (metal, ICA or Y-TZP. The IF of the crowns was measured using the replica technique, which employs a light body polyvinyl siloxane impression material to simulate the cement layer thickness. The data were analyzed according to the surfaces obtained for the occlusal space (OS, axial space (AS and total mean (TM using two-way ANOVA with Tukey ’s multiple comparison test (p<0.05. RESULTS: No differences among the different areas were detected in the MC group. For the Y-TZP and ICA groups, AS was statistically lower than both OS and TM. No differences in AS were observed among the groups. However, OS and TM showed significantly higher values for ICA and Y-TZP groups than MC group. Comparisons of ICA and Y-TZP revealed that OS was significantly lower for Y-TZP group, whereas no differences were observed for TM. CONCLUSIONS: The total mean achieved by all groups was within the range of clinical acceptability. However, the metal-ceramic group demonstrated significantly lower values than the all-ceramic groups, especially in OS.

  8. Internal fit of two all-ceramic systems and metal-ceramic crowns

    Science.gov (United States)

    MARTINS, Leandro Moura; LORENZONI, Fabio Cesar; de MELO, Alcides Oliveira; da SILVA, Luciana Mendonça; de OLIVEIRA, José Luiz G.; de OLIVEIRA, Pedro Cesar Garcia; BONFANTE, Gerson

    2012-01-01

    Objectives The aim of this study was to investigate the internal fit (IF) of glass-infiltrated alumina (ICA - In-Ceram Alumina), yttria-stabilized tetragonal zirconia polycrystals (Y-TZP - IPS e.max ZirCAD), and metal-ceramic (MC - Ni-Cr alloy) crowns. Material and Methods Sixty standardized resin-tooth replicas of a maxillary first molar were produced for crown placement and divided into 3 groups (n=20 each) according to the core material used (metal, ICA or Y-TZP). The IF of the crowns was measured using the replica technique, which employs a light body polyvinyl siloxane impression material to simulate the cement layer thickness. The data were analyzed according to the surfaces obtained for the occlusal space (OS), axial space (AS) and total mean (TM) using two-way ANOVA with Tukey's multiple comparison test (p<0.05). Results No differences among the different areas were detected in the MC group. For the Y-TZP and ICA groups, AS was statistically lower than both OS and TM. No differences in AS were observed among the groups. However, OS and TM showed significantly higher values for ICA and Y-TZP groups than MC group. Comparisons of ICA and Y-TZP revealed that OS was significantly lower for Y-TZP group, whereas no differences were observed for TM. Conclusions The total mean achieved by all groups was within the range of clinical acceptability. However, the metal-ceramic group demonstrated significantly lower values than the all-ceramic groups, especially in OS. PMID:22666843

  9. Reduction of magnetic grain size of perpendicular recording media with CoCrW seed layer

    Science.gov (United States)

    Inamura, R.; Toyoda, T.; Tanaka, T.; Uzumaki, T.

    2009-04-01

    We report the use of CoCrW seed layer (SL) for making the fine grain granular structure and high crystalline orientation of CoCrPt-oxide magnetic recording layer. It is found that CoCrW SL should be of amorphouslike structure to make fine grain of CoCrPt-oxide magnetic layer. Moreover, the smooth surface of CoCrW SL provides high crystalline orientation of the CoCrPt-oxide magnetic layer.

  10. High Temperature Interactions of Metallic Matrices with Ceramic Reinforcements

    Science.gov (United States)

    1990-12-31

    temperatura range were extensive; various metal silicides, metalIcarbides, ternary metal-slilcon-carbides, and unreacted carbon were formed as layered...Couples 3.2.1 Preparation of SiC Ceramic: The polycrystalline SiC substrates, designated as Hexoloy, were obtained from the Carborundum Corporation ...and was received from Engelhard Corporation . The metal pieces were cut into a similar size to that of the SiC, mechanically ground with #600 SiC papers

  11. Ferrites and ceramic composites

    CERN Document Server

    Jotania, Rajshree B

    2013-01-01

    The Ferrite term is used to refer to all magnetic oxides containing iron as major metallic component. Ferrites are very attractive materials because they simultaneously show high resistivity and high saturation magnetization, and attract now considerable attention, because of the interesting physics involved. Typical ferrite material possesses excellent chemical stability, high corrosion resistivity, magneto-crystalline anisotropy, magneto-striction, and magneto-optical properties. Ferrites belong to the group of ferrimagnetic oxides, and include rare-earth garnets and ortho-ferrites. Several

  12. Multifunctional Ceramic Nanostructured Coatings

    Science.gov (United States)

    2010-12-01

    Stansky D.V., Petrznik M.I., Levashov E.A., Mavrin B.N. // Surf. Coat. Tech. -2007.-V.201.- P . 6143-6147. 7. Kauffmann F., Dehm G., Schier V...5a. CONTRACT NUMBER STCU Registration No: P -253 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Dr. Anatolij Tarasovich Pugachov...lead to the increase in crystalline lattice rigidness, hardness, melting temperature and oxidation resistance in Me2B→MeB→ MeB2 line [13]. Boron p

  13. Practice-based clinical evaluation of ceramic single crowns after at least five years.

    Science.gov (United States)

    Dhima, Matilda; Paulusova, Vladimira; Carr, Alan B; Rieck, Kevin L; Lohse, Christine; Salinas, Thomas J

    2014-02-01

    Long-term practice-based clinical evaluations of various contemporary ceramic crown restorations from multiple practitioners are limited. The aims of this study were to evaluate the clinical performance of ceramic single crowns and to identify factors that influence their clinical performance. Ceramic single crowns that had been placed at the Mayo Clinic and in function since 2005 were identified and included in the study. The restorations were examined clinically, radiographically, and with photographs. Modified United States Public Health Services criteria were used for the clinical evaluation. The ceramic systems evaluated were bilayer and monolayer. Fifty-nine patients (41 women, 18 men) with 226 single teeth and implants restored with single ceramic crowns were identified. The mean duration from insertion date to study examination date was 6.1 years. Thirteen restorations (6%) were replaced at a mean 3.3 years after insertion date (range, 0.1-6.1 years). Estimated replacement-free survival rates (95% confidence interval [CI]; number of teeth/implants still at risk) at 5 years after insertion date were 95.1% (95% CI, 92.2-98.1; 153) and at 10 years were 92.8% (95% CI, 89.1-96.8; 8). The most common reason for replacement was fracture to the core of posterior layered ceramic crowns. The most commonly used luting agent was resin-modified ionomer cement. Most restorations exhibited clinically acceptable marginal integrity, shade, no caries recurrence, and no periapical pathology. The clinical performance of ceramic single crowns at 5 and 10 years supports their application in all areas of the mouth. With the majority of fractures to the core occurring early in the lifetime of layered ceramic posterior crowns, consideration of other monolithic ceramic systems for posterior crowns is advised. Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1991-03-30

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

  15. Comparison of the microstructure and composition of aboriginal ceramics, from indigenous site Caninhas, with the obtained ones in the region; Comparacao da microestrutura e da composicao de ceramicas indigenas provenientes do sitio arqueologico Caninhas, com as obtidas atualmente na regiao

    Energy Technology Data Exchange (ETDEWEB)

    Matos, C.C.; Nakano, F.P.; Taguchi, S.P.; Camargo-Vernilli, D., E-mail: cristhian@alunos.eel.usp.b [Universidade de Sao Paulo (DEMAR/EEL/USP), Lorena, SP (Brazil). Escola de Engenharia de Lorena. Dept. de Engenharia de Materiais; Ribeiro, R.B.; Rosa, S.J. L. [Faculdades Integradas Teresa D' Avila (FATEA), Lorena, SP (Brazil). Rede Salesianas. Dept. de Desenho Industrial

    2009-07-01

    The archaeological site of Caninhas is made of funeral and combustion structures and various objects of aboriginal daily use. These parts and fragments were safe and inventoried, constituting approximately 4000 units. The objective of this project was to analyze the microstructure and composition of archaeological ceramics, and ceramics made of argil current of the zone. The crystalline phases were identified by X-Rays Diffraction (XRD), elementary composition was obtained by X-Rays Fluorescence (XRF) and Energy Dispersive Spectrometry (EDS), and the microstructure was evaluated by Scanning Electron Microscope (SEM). Composition and microstructure of archaeological ceramics are different of current ceramics, indicating the effect of lixiviation in function of the time and the microstructural evolution due different ceramic processing. These results are valuable for the archaeological area studies, mainly for the cultural denoting which represents. The relation between some studies is basic to add knowledge: use of the ceramic materials engineering for archaeology application. (author)

  16. A low-cost mullite-titania composite ceramic hollow fiber microfiltration membrane for highly efficient separation of oil-in-water emulsion.

    Science.gov (United States)

    Zhu, Li; Chen, Mingliang; Dong, Yingchao; Tang, Chuyang Y; Huang, Aisheng; Li, Lingling

    2016-03-01

    Oil-in-water (O/W) emulsion is considered to be difficult to treat. In this work, a low-cost multi-layer-structured mullite-titania composite ceramic hollow fiber microfiltration membrane was fabricated and utilized to efficiently remove fine oil droplets from (O/W) emulsion. In order to reduce membrane cost, coal fly ash was effectively recycled for the first time to fabricate mullite hollow fiber with finger-like and sponge-like structures, on which a much more hydrophilic TiO2 layer was further deposited. The morphology, crystalline phase, mechanical and surface properties were characterized in details. The filtration capability of the final composite membrane was assessed by the separation of a 200 mg·L(-1) synthetic (O/W) emulsion. Even with this microfiltration membrane, a TOC removal efficiency of 97% was achieved. Dilute NaOH solution backwashing was used to effectively accomplish membrane regeneration (∼96% flux recovery efficiency). This study is expected to guide an effective way to recycle waste coal fly ash not only to solve its environmental problems but also to produce a high-valued mullite hollow fiber membrane for highly efficient separation application of O/W emulsion with potential simultaneous functions of pure water production and oil resource recovery. Copyright © 2015 Elsevier Ltd. All rights reserved.

  17. Dental ceramics coated with bioactive glass: Surface changes after exposure in a simulated body fluid under static and dynamic conditions

    Science.gov (United States)

    Papadopoulou, L.; Kontonasaki, E.; Zorba, T.; Chatzistavrou, X.; Pavlidou, E.; Paraskevopoulos, K.; Sklavounos, S.; Koidis, P.

    2003-07-01

    Bioactive materials develop a strong bond with living tissues through a carbonate-containing hydroxyapatite layer, similar to that of bone. The fabrication of a thin bioactive glass coating on dental ceramics used in metal-ceramic restorations, could provide a bioactive surface, which in combination with a tissue regenerative technique could lead to periodontal tissues attachment. The aim of this study was the in vitro investigation of the surface structure changes of dental ceramics used in metal-ceramic restorations, coated with a bioactive glass heat-treated at 950 °C, after exposure in a simulated body fluid (SBF) under two different soaking conditions. Coating of dental ceramics with a bioactive glass resulted in the formation of a stable and well bonded with the ceramic substrate thin layer. The growth of a well-attached carbonate apatite layer on their surface after immersion in a simulated body fluid is well evidenced under both experimental conditions, although in static environment the rate of apatite growth is constant and the grown layers seem to be more dense and compact compared with the respective layers observed on specimens under dynamic conditions.

  18. A comparative study of progressive wear of four dental monolithic, veneered glass-ceramics.

    Science.gov (United States)

    Zhang, Zhenzhen; Yi, Yuanping; Wang, Xuesong; Guo, Jiawen; Li, Ding; He, Lin; Zhang, Shaofeng

    2017-10-01

    This study evaluated the wear performance and wear mechanisms of four dental glass-ceramics, based on the microstructure and mechanical properties in the progressive wear process. Bar (N = 40, n = 10) and disk (N = 32, n = 8) specimens were prepared from (A) lithium disilicate glass-ceramic (LD), (B) leucite reinforced glass-ceramic (LEU), (C) feldspathic glass-ceramic (FEL), and (D) fluorapatite glass-ceramic (FLU). The bar specimens were tested for three-point flexural strength, hardness, fracture toughness and elastic modulus. The disk specimens paired with steatite antagonists were tested in a pin-on-disk tribometer with 10N up to 1000,000 wear cycles. The wear analysis of glass-ceramics was performed using a 3D profilometer after every 200,000 wear cycles. Wear loss of steatite antagonists was calculated by measuring the weight and density using sensitive balance and Archimedes' method. Wear morphologies and microstructures were analyzed by scanning electron microscopy (SEM). The crystalline phase compositions were determined using X-ray diffraction (XRD). One-way analysis of variance (ANOVA) was used to analyze the data. Multiple pair-wise comparison of means was performed by Tukey's post-hoc test. LD showed the highest fracture toughness, flexural strength, elastic modulus and crystallinity, followed by LEU and FEL, and FLU showed the lowest. However, the hardness of LD was lower than all the other three types of ceramics. For steatite antagonists, LD produced the least wear loss of antagonist, followed by LEU and FEL, and FLU had the most wear loss. For glass-ceramic materials, LD exhibited similar wear loss as LEU, but more than FLU and FEL did. Moreover, fracture occurred on the wear surface of FLU. In the progressive wear process, veneering porcelains showed better wear resistance but fluorapatite veneering porcelains appeared fracture surface. Monolithic lithium disilicate glass-ceramics with higher mechanical properties showed more wear loss, however

  19. Agglomeration of ceramic powders

    Science.gov (United States)

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

    1989-01-01

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

  20. Creep in electronic ceramics

    Energy Technology Data Exchange (ETDEWEB)

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

    2000-04-27

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