WorldWideScience

Sample records for resistance structural ceramics

  1. Alkali corrosion resistant coatings and ceramic foams having superfine open cell structure and method of processing

    Science.gov (United States)

    Brown, Jr., Jesse J.; Hirschfeld, Deidre A.; Li, Tingkai

    1993-12-07

    Alkali corrosion resistant coatings and ceramic foams having superfine open cell structure are created using sol-gel processes. The processes have particular application in creating calcium magnesium zirconium phosphate, CMZP, coatings and foams.

  2. Structural Ceramics Database

    Science.gov (United States)

    SRD 30 NIST Structural Ceramics Database (Web, free access)   The NIST Structural Ceramics Database (WebSCD) provides evaluated materials property data for a wide range of advanced ceramics known variously as structural ceramics, engineering ceramics, and fine ceramics.

  3. INVESTIGATION OF PLASMA WEAR RESISTANCE COATING STRUCTURE ON BASIS OF OXIDE CERAMICS WITH INCLUSIONS OF SOLID LUBRICATION

    Directory of Open Access Journals (Sweden)

    F. I. Panteleenko

    2013-01-01

    Full Text Available The paper describes an investigation of the structure, chemical and phase composition of wear resistance coatings on the basis of  oxide ceramics with inclusions of  solid lubrication.

  4. 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

  5. Corrosion resistant ceramic materials

    Science.gov (United States)

    Kaun, Thomas D.

    1996-01-01

    Ceramic materials which exhibit stability in severely-corrosive environments having high alkali-metal activity, high sulfur/sulfide activity and/or molten halides at temperatures of 200.degree.-550.degree. C. or organic salt (including SO.sub.2 and SO.sub.2 Cl.sub.2) at temperatures of 25.degree.-200.degree. C. These sulfide ceramics form stoichiometric (single-phase) compounds with sulfides of Ca, Li, Na, K, Al, Mg, Si, Y, La, Ce, Ga, Ba, Zr and Sr and show melting-points that are sufficiently low and have excellent wettability with many metals (Fe, Ni, Mo) to easily form metal/ceramic seals. Ceramic compositions are also formulated to adequately match thermal expansion coefficient of adjacent metal components.

  6. Improved of the Nanolaminate - Ceramic by the Additional of Aluminium to used in Higher Resistance Hydraulic Structures

    Directory of Open Access Journals (Sweden)

    Jawad Kadhim Abbood

    2016-12-01

    Full Text Available It has been tried in this research to introduce this type of new structural materials as reproducible industrial materials and overtake some production obstacles by exploring the direction of chemistry structure relation. The compacted samples have been prepared from elemental powders (Titanium, Aluminum and Black Carbon using the powder technology techniques. They have been dispersed in different concentrations (Ti-Al-C and different molar ratios due to the change in the Ti to Al concentrations. Thus the effect of Al concentration on MAX phase evolution in the Ti-Al-C system has been investigated and discussed. Therefore, the concentration of Al has improved the applications of water resource structures, and that alloy, especially in corrosion resistance and under water, has proved structures as well as pipes because the Al has created the layer that protects this ceramic from hard and nature conditions , So the Al metal lead to use this ceramic in loading bearing structures such as bridges and high impact resistance such as Dams. The effects of cold and hot pressing as well as sintering in different temperatures are investigated. Phase evolution is discovered by X-ray diffraction (XRD, and SEM. Micro hardness test and Archimedes method is used to measure the density and porosity percentage. No evidence for the direct formation of MAX phases from elemental powders is foud which may explain the need of high temperatures to produce such phases since the breaking of bonds is required for the intermediate phase.

  7. Radiation resistant ceramic matrix composites

    International Nuclear Information System (INIS)

    Jones, R.H.; Steiner, D.; Heinisch, H.L.; Newsome, G.A.; Kerch, H.M.

    1997-01-01

    Ceramic matrix composites are of interest for nuclear applications because of their high-temperature properties, corrosion resistance, fracture toughness relative to monolithic ceramics, and low neutron activation and after heat. Evaluations of the radiation resistance of commercially available SiC/SiC composites have revealed their promise for this application, but also the need for further development to achieve the desired performance. This paper summarizes the results of a workshop cosponsored by the Offices of Fusion Energy and Basic Energy Sciences of the US Department of Energy and Lockheed-Martin Corporation with forty attendees from national laboratories, universities and industry. A number of promising routes for optimizing the radiation stability of ceramic matrix composites were identified at this workshop. These routes included the newer, more stoichiometric fibers and alternate fiber/matrix interfaces and matrix processing routes. (orig.)

  8. Influence of ceramic thickness and ceramic materials on fracture resistance of posterior partial coverage restorations.

    Science.gov (United States)

    Bakeman, E M; Rego, N; Chaiyabutr, Y; Kois, J C

    2015-01-01

    This study evaluated the influence of ceramic thickness and ceramic materials on fracture resistance of posterior partial coverage ceramic restorations. Forty extracted molars were allocated into four groups (n=10) to test for two variables: 1) the thickness of ceramic (1 mm or 2 mm) and 2) the ceramic materials (a lithium disilicate glass-ceramic [IPS e.max] or leucite-reinforced glass ceramic [IPS Empress]). All ceramic restorations were luted with resin cement (Variolink II) on the prepared teeth. These luted specimens were loaded to failure in a universal testing machine, in the compression mode, with a crosshead speed of 1.0 mm/min. The data were analyzed using two-way analysis of variance and the Tukey Honestly Significantly Different multiple comparison test (α =0.05). The fracture resistance revealed a significant effect for materials (pceramic was not significant (p=0.074), and the interaction between the thickness of ceramic and the materials was not significant (p=0.406). Mean (standard deviation) fracture resistance values were as follows: a 2-mm thickness of a lithium disilicate bonded to tooth structure (2505 [401] N) revealed a significantly higher fracture resistance than did a 1-mm thickness of leucite-reinforced (1569 [452] N) and a 2-mm thickness of leucite-reinforced ceramic bonded to tooth structure (1716 [436] N) (pceramic at 1-mm thickness (2105 [567] N) and at 2-mm thickness. Using a lithium disilicate glass ceramic for partial coverage restoration significantly improved fracture resistance compared to using a leucite-reinforced glass ceramic. The thickness of ceramic had no significant effect on fracture resistance when the ceramics were bonded to the underlying tooth structure.

  9. Ablation Resistant Zirconium and Hafnium Ceramics

    Science.gov (United States)

    Bull, Jeffrey (Inventor); White, Michael J. (Inventor); Kaufman, Larry (Inventor)

    1998-01-01

    High temperature ablation resistant ceramic composites have been made. These ceramics are composites of zirconium diboride and zirconium carbide with silicon carbide, hafnium diboride and hafnium carbide with silicon carbide and ceramic composites which contain mixed diborides and/or carbides of zirconium and hafnium. along with silicon carbide.

  10. Advanced ceramic in structural engineering

    OpenAIRE

    Alonso Rodea, Jorge

    2012-01-01

    The work deals with "Advanced Ceramics in Structural Engineering”. Throughout this work we present the different types of ceramic that are currently in wider use, and the main research lines that are being followed. Ceramics have very interesting properties, both mechanical and electrical and refractory where we can find some of the most interesting points of inquiry. Through this work we try tounderstand this complex world, analyzing both general and specific properties of ...

  11. Mechanical behaviour of structural ceramics

    Directory of Open Access Journals (Sweden)

    Bueno, S.

    2007-06-01

    Full Text Available The use of ceramic materials in structural applications is limited by the lack of reliability associated with brittle fracture behaviour. In order to extend the structural use of ceramics, the design of microstructures which exhibit flaw tolerance due to toughening mechanisms which produce an increase in crack growth resistance during crack propagation has been proposed. This work is a review of the mechanical behaviour of structural ceramic materials and its characterisation. Firstly, the basic brittle fracture parameters and the statistical criteria to determine the probability of exceeding the safety factors demanded for a particular application are analysed. Then, the toughening mechanisms which can be developed in the materials through microstructural design as well as the mechanical characterisation of toughened ceramics are discussed. The experimental values of linear elastic fracture toughness parameters (critical stress intensity factor, KIC, and critical energy release rate, GIC are not intrinsic properties for toughened materials and depend on crack length and the loading system. In this work, the different mechanical parameters proposed to characterise such materials are reviewed. The following fracture parameters are analysed: work of fracture (γWOF, critical J-integral value (JIC and R-curve. For the determination, stable fracture tests are proposed in order to ensure that the energy provided during the test is no more than the necessary one for crack propagation.

    El uso de los materiales cerámicos en aplicaciones estructurales está limitado por la falta de fiabilidad asociada a su comportamiento frágil durante la fractura. Para extender su aplicación se ha propuesto el diseño de microestructuras que presenten tolerancia a los defectos debido a la actuación de mecanismos de refuerzo. Este trabajo es una puesta al día sobre el estudio del comportamiento mecánico de los materiales cerámicos estructurales y su

  12. Preparation of a dense, polycrystalline ceramic structure

    Science.gov (United States)

    Cooley, Jason; Chen, Ching-Fong; Alexander, David

    2010-12-07

    Ceramic nanopowder was sealed inside a metal container under a vacuum. The sealed evacuated container was forced through a severe deformation channel at an elevated temperature below the melting point of the ceramic nanopowder. The result was a dense nanocrystalline ceramic structure inside the metal container.

  13. Biocompatible wear-resistant thick ceramic coating

    Directory of Open Access Journals (Sweden)

    Vogt Nicola

    2016-09-01

    Full Text Available Sensitisation to immunologically active elements like chromium, cobalt or nickel and debris particle due to wear are serious problems for patients with metallic implants. We tested the approach of using a hard and thick ceramic coating as a wear-resistant protection of titanium implants, avoiding those sensitisation and foreign body problems. We showed that the process parameters strongly influence the coating porosity and, as a consequence, also its hardness.

  14. All ceramic structure for molten carbonate fuel cell

    Science.gov (United States)

    Smith, James L.; Kucera, Eugenia H.

    1992-01-01

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

  15. Frictional Resistance of Three Types of Ceramic Brackets

    Directory of Open Access Journals (Sweden)

    Claire L Williams

    2014-01-01

    Full Text Available Objectives: To investigate the static frictional resistance at the bracket/archwire interface in two recently introduced bracket systems and compare them to conventional ceramic and conventional metal bracket systems. Three variables were considered including the bracket system, archwire type and archwire angulation. Material and Methods: Four bracket systems were tested in vitro: Self ligating ceramic, ceramic with metal slot and module, conventional ceramic with module and conventional metal with module. A specially constructed jig and an Instron testing machine were used to measure the static frictional resistance for 0.014 inches round and 0.018 x 0.025 inches rectangular stainless steel wires at 0° and 7° angulations. Main outcome measures: static frictional force at the bracket/archwire interface; recorded and measured in units of force (Newtons. Results: Self ligating ceramic and metal slot ceramic bracket systems generated significantly less static frictional resistance than conventional ceramic bracket systems with the wire at both angulations (P < 0.05. Changing the wire from 0.014 round to 0.018 x 0.025 rectangular wire significantly increased frictional forces for metal slot ceramic and conventional metal bracket systems (P < 0.01. Increasing wire angulation significantly increased frictional resistance at the bracket/archwire interface for all four types of bracket systems tested (P < 0.001. Conclusions: Compared to conventional ceramic, self ligating ceramic and metal slot ceramic bracket systems should give improved clinical performance, matching that of conventional metal brackets.

  16. High temperature ceramic/metal joint structure

    Science.gov (United States)

    Boyd, Gary L. (Inventor)

    1991-01-01

    A high temperature turbine engine includes a hybrid ceramic/metallic rotor member having ceramic/metal joint structure. The disclosed joint is able to endure higher temperatures than previously possible, and aids in controlling heat transfer in the rotor member.

  17. High performance structural ceramics for nuclear industry

    International Nuclear Information System (INIS)

    Pujari, Vimal K.; Faker, Paul

    2006-01-01

    A family of Saint-Gobain structural ceramic materials and products produced by its High performance Refractory Division is described. Over the last fifty years or so, Saint-Gobain has been a leader in developing non oxide ceramic based novel materials, processes and products for application in Nuclear, Chemical, Automotive, Defense and Mining industries

  18. Insulating Structural Ceramics Program, Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Andrews, Mark J.; Tandon, Raj; Ott, Eric; Hind, Abi Akar; Long, Mike; Jensen, Robert; Wheat, Leonard; Cusac, Dave; Lin, H. T.; Wereszczak, Andrew A.; Ferber, Mattison K.; Lee, Sun Kun; Yoon, Hyung K.; Moreti, James; Park, Paul; Rockwood, Jill; Boyer, Carrie; Ragle, Christie; Balmer-Millar, Marilou; Aardahl, Chris; Habeger, Craig; Rappe, Ken; Tran, Diana; Koshkarian, Kent; Readey, Michael

    2005-11-22

    New materials and corresponding manufacturing processes are likely candidates for diesel engine components as society and customers demand lower emission engines without sacrificing power and fuel efficiency. Strategies for improving thermal efficiency directly compete with methodologies for reducing emissions, and so the technical challenge becomes an optimization of controlling parameters to achieve both goals. Approaches being considered to increase overall thermal efficiency are to insulate certain diesel engine components in the combustion chamber, thereby increasing the brake mean effective pressure ratings (BMEP). Achieving higher BMEP rating by insulating the combustion chamber, in turn, requires advances in material technologies for engine components such as pistons, port liners, valves, and cylinder heads. A series of characterization tests were performed to establish the material properties of ceramic powder. Mechanical chacterizations were also obtained from the selected materials as a function of temperature utilizing ASTM standards: fast fracture strength, fatique resistance, corrosion resistance, thermal shock, and fracture toughness. All ceramic materials examined showed excellent wear properties and resistance to the corrosive diesel engine environments. The study concluded that the ceramics examined did not meet all of the cylinder head insert structural design requirements. Therefore we do not recommend at this time their use for this application. The potential for increased stresses and temperatures in the hot section of the diesel engine combined with the highly corrosive combustion products and residues has driven the need for expanded materials capability for hot section engine components. Corrosion and strength requirements necessitate the examination of more advanced high temperture alloys. Alloy developments and the understanding of processing, structure, and properties of supperalloy materials have been driven, in large part, by the gas

  19. Radiation effects on structural ceramics in fusion

    International Nuclear Information System (INIS)

    Hopkins, G.R.; Price, R.J.; Trester, P.W.

    1986-01-01

    Ceramics are required to serve in a conventional role as electrical and thermal insulators and dielectrics in fusion power reactors. In addition, certain ceramic materials can play a unique structural role in fusion power reactors by virtue of their very low induced radioactivity from fusion neutron capture. The aspects of safety, long-term radioactive waste management, and personnel access for maintenance and repair can all be significantly improved by applying the low-activation ceramics to the structural materials of the first-wall and blanket regions of a fusion reactor. Achievement of long service life at high structural loads and thermal stresses on the materials exposed to high-radiation doses presents a critical challenge for fusion. In this paper, we discuss radiation effects on structural ceramics for fusion application

  20. Geopolymers for Structural Ceramic Applications

    Science.gov (United States)

    2006-08-31

    Stow, Ohio 44224 Abstract Geopolymers , also called geo- cements and low-temperature synthesized glasses, are a class of cementious materials that do...Applications of geopolymers have included ceramic matrix composites,ŕ, 3 waste encapsulation 9-11and alternative cements .7,12,14 As adhesives...and H. Schneider, The American Ceramic Society, Westerville, OH, 2003. 3J. Bell and W. M. Kriven, "Nanoporosity in geopolymeric cements " pp. 590-591

  1. High-temperature materials and structural ceramics

    International Nuclear Information System (INIS)

    1990-01-01

    This report gives a survey of research work in the area of high-temperature materials and structural ceramics of the KFA (Juelich Nuclear Research Center). The following topics are treated: (1) For energy facilities: ODS materials for gas turbine blades and heat exchangers; assessment of the remaining life of main steam pipes, material characterization and material stress limits for First-Wall components; metallic and graphitic materials for high-temperature reactors. (2) For process engineering plants: composites for reformer tubes and cracking tubes; ceramic/ceramic joints and metal/ceramic and metal/metal joints; Composites and alloys for rolling bearing and sliding systems up to application temperatures of 1000deg C; high-temperature corrosion of metal and ceramic material; porous ceramic high-temperature filters and moulding coat-mix techniques; electrically conducting ceramic material (superconductors, fuel cells, solid electrolytes); high-temperature light sources (high-temperature chemistry); oil vapor engines with caramic components; ODS materials for components in diesel engines and vehicle gas turbines. (MM) [de

  2. Structure and properties of interfaces in ceramics

    International Nuclear Information System (INIS)

    Bonnell, D.; Ruehle, M.; Chowdhry, U.

    1995-01-01

    The motivation for the symposium was the observation that interfaces in crystallographically and compositionally complex systems often dictate the performance and reliability of devices that utilize functional ceramics. The current level of understanding of interface-property relations in silicon-based devices required over 30 years of intensive research. Similar issues influence the relationship between atomic bonding at interfaces and properties in functional ceramic systems. The current understanding of these complex interfaces does not allow correlation between atomic structure and interface properties, in spite of their importance to a number of emerging technologies (wireless communications, radar-based positioning systems, sensors, etc.). The objective of this symposium was to focus attention on these fundamental issues by featuring recent theoretical and experimental work from various disciplines that impact the understanding of interface chemistry, structure, and properties. The emphasis was on relating properties of surfaces and interfaces to structure through an understanding of atomic level phenomena. Interfaces of interest include metal/ceramic, ceramic/ceramic, ceramic/vapor, etc., in electronic, magnetic, optical, ferroelectric, piezoelectric, and dielectric applications. Sixty one papers have been processed separately for inclusion on the data base

  3. Frost-resistance of red ceramic products

    Directory of Open Access Journals (Sweden)

    Ramires, M. V. V.

    2000-02-01

    Full Text Available The present work is a study about degradation occurring with red ceramics whenever they are exposed to the environmental conditions of a cold and humid climate. Four different types of clay from Rio Grande do Sul were studied: two of them from the Serra Geral formation, and the other two from the formation of Strada Nova, which are commonly used to make roof tiles. The clay was characterised to identify its chemical and mineralogical composition. Also the physical properties were researched. In the ceramic processing, the pressure with four different sintering temperatures (850ºC, 900ºC, 950ºC, and 1000ºC at three different intervals (3, 12, and 24 hours were used. The ceramic materials thus obtained were characterised according to their physical properties (water absorption, total density, porosity, and porous size, and mechanical (mechanical resistance over four points. For the characterisation of the degradation mechanism, some trials were carried out to obtain the coefficient of saturation and on frost and defrost cycles. The microstructural analysis was made with a scanning electronic microscopy. On the basis of the results obtained, a model for the degradation mechanism is presented, and a degradation factor which relates the total volume of mesopores to the standard size of mesopores is suggested. It was concluded that the red ceramic products more prone to be frost-resistant are those presenting a degradation factor below 100.

    Se estudia la degradación que sufre la cerámica roja cuando se expone a la acción de los climas fríos e húmedos. La experimentación se ha realizado con cuatro arcillas de la son expuestas a los climas fríos y húmedos. Se investigaron cuatro diferentes arcillas de la provincia del Rio Grande do Sul, que se emplean tradicionalmente en la fabricación de tejas. Dos de ellas pertenecen a la formación de la Serra Geral y las otras dos de la formación Estrada Nova. La caracterización de las arcillas

  4. Ceramic materials on perovskite-type structure for electronic applications

    International Nuclear Information System (INIS)

    Surowiak, Z.

    2003-01-01

    Ceramic materials exhibiting the perovskite-type structure constitute among others, resource base for many fields of widely understood electronics (i.e., piezoelectronics, accustoelectronics, optoelectronics, computer science, tele- and radioelectronics etc.). Most often they are used for fabrication of different type sensors (detectors), transducers, ferroelectric memories, limiters of the electronic current intensity, etc., and hence they are numbered among so-called intelligent materials. Prototype structure of this group of materials is the structure of the mineral called perovskite (CaTiO 3 ). By means of right choice of the chemical composition of ABO 3 and deforming the regular perovskite structure (m3m) more than 5000 different chemical compounds and solid solutions exhibiting the perovskite-type structure have been fabricated. The concept of perovskite functional ceramics among often things ferroelectric ceramics, pyroelectric ceramics, piezoelectric ceramics, electrostrictive ceramics, posistor ceramics, superconductive ceramics and ferromagnetic ceramics. New possibilities of application of the perovskite-type ceramics are opened by nanotechnology. (author)

  5. Fracture resistance of teeth restored with all-ceramic inlays and onlays: an in vitro study.

    Science.gov (United States)

    Saridag, S; Sevimay, M; Pekkan, G

    2013-01-01

    Fracture resistance of inlays and onlays may be influenced by the quantity of the dental structure removed and the restorative materials used. The purpose of this in vitro study was to evaluate the effects of two different cavity preparation designs and all-ceramic restorative materials on the fracture resistance of the tooth-restoration complex. Fifty mandibular third molar teeth were randomly divided into the following five groups: group 1: intact teeth (control); group 2: inlay preparations, lithium-disilicate glass-ceramic (IPS e.max Press, Ivoclar Vivadent AG, Schaan, Liechtenstein); group 3: inlay preparations, zirconia ceramic (ICE Zirkon, Zirkonzahn SRL, Gais, Italy); group 4: onlay preparations, lithium-disilicate glass-ceramic (IPS e.max Press); and group 5: onlay preparations, zirconia ceramic (ICE Zirkon). The inlay and onlay restorations were adhesively cemented with dual polymerizing resin cement (Variolink II, Ivoclar Vivadent AG). After thermal cycling (5° to 55°C × 5000 cycles), specimens were subjected to a compressive load until fracture at a crosshead speed of 0.5 mm/min. Statistical analyses were performed using one-way analysis of variance and Tukey HSD tests. The fracture strength values were significantly higher in the inlay group (2646.7 ± 360.4) restored with lithium-disilicate glass-ceramic than those of the onlay group (1673.6 ± 677) restored with lithium-disilicate glass-ceramic. The fracture strength values of teeth restored with inlays using zirconia ceramic (2849 ± 328) and onlays with zirconia ceramic (2796.3 ± 337.3) were similar to those of the intact teeth (2905.3 ± 398.8). In the IPS e.max Press groups, as the preparation amount was increased (from inlay to onlay preparation), the fracture resistance was decreased. In the ICE Zirkon ceramic groups, the preparation type did not affect the fracture resistance results.

  6. Structural behaviour of nitrogen in oxide ceramics

    International Nuclear Information System (INIS)

    Ghauri, K.M.

    1997-01-01

    The solubility of nitrogen in molten oxides has significant consideration for two quite different types of engineering materials. The implication of a knowledge of the role of nitrogen in these oxides for refining high nitrogen steels in obvious but similar nitrogen-bearing oxide melts are of critical importance in the densification of silicon nitride ceramics. Present paper discusses structural behaviour and phase equilibria qualitatively in the light of knowledge available on slag structure through infrared and x-ray diffraction. Nitrogen solubility in glasses and related sialon based ceramics may be of paramount importance to understand the role of nitrogen in these materials as these oxides are similar in composition, structure and characteristics to sintering glasses in nitrogen ceramics. It is quite logical to infer that the same oxide model can be applied in order to massively produce nitrogen alloyed steels which are actively competing to be the materials of the next century. (author)

  7. ASSESSMENT OF CERAMIC TILE FROST RESISTANCE BY MEANS OF THE FREQUENCY INSPECTION METHOD

    Directory of Open Access Journals (Sweden)

    MICHAL MATYSÍK

    2011-06-01

    Full Text Available The paper presents some results of our experimental analysis of ceramic cladding element frost resistance, particular attention being paid to the application of the frequency inspection method. Three different sets of ceramic tiles of the Ia class to EN 14 411 B standard made by various manufacturers have been analyzed. The ceramic tiles under investigation have been subjected to freeze-thaw-cycle-based degradation in compliance with the relevant ČSN EN ISO 10545-12 standard. Furthermore, accelerated degradation procedure has been applied to selected test specimens, consisting in reducing the temperature of water soaked ceramic tiles in the course of the degradation cycles down –70°C. To verify the correctness of the frequency inspection results, additional physical properties of the ceramic tiles under test have been measured, such as, the ceramic tile strength limit, modulus of elasticity and modulus of deformability, resulting from the flexural tensile strength tests, integrity defect and surface micro-geometry tracking. It has been proved that the acoustic method of frequency inspection is a sensitive indicator of the structure condition and can be applied to the ceramic cladding element frost resistance and service life prediction assessment.

  8. High-frequency characteristics of glass/ceramic composite and alumina multilayer structures

    International Nuclear Information System (INIS)

    Niwa, K.; Suzuki, H.; Yokoyama, H.; Kamechara, N.; Tsubone, K.; Tanisawa, H.; Sugiki, H.

    1990-01-01

    This paper reports the transmission characteristics of glass/ceramic composite (borosilicate glass/alumina) and alumina multilayer structures examined. The triplate stripline formed in the glass/ceramic multilayer shows low conductor and dielectric loss. Alumina multilayer, however, has twice the transmission loss at 10 GHz, because the resistivity of W in the alumina multilayer is higher than the Cu in the glass/ceramic multilayer. Crosstalk between striplines in the glass/ceramics is less than -80 dB up to 11 GHz and 9 GHz for alumina

  9. Frost-resistance of red ceramic products

    OpenAIRE

    Ramires, M. V. V.; Madruga, T. P.; Bergman, C. P.

    2000-01-01

    The present work is a study about degradation occurring with red ceramics whenever they are exposed to the environmental conditions of a cold and humid climate. Four different types of clay from Rio Grande do Sul were studied: two of them from the Serra Geral formation, and the other two from the formation of Strada Nova, which are commonly used to make roof tiles. The clay was characterised to identify its chemical and mineralogical composition. Also the physical properties were researched. ...

  10. Fabrication of low specific resistance ceramic carbon composites by ...

    Indian Academy of Sciences (India)

    2017-09-07

    Sep 7, 2017 ... the produced carbon is responsible for low electrical specific resistance of the ceramic carbon composites. References. [1] Takahashi M, Adachi K, Menchavez R L and Fuji M 2006 J. Mater. Sci. 41 1965. [2] ShuKMandTuGC2003Int. J. Machine Tools Manufacture43. 845. [3] Mikeska K R 1997 United States ...

  11. Characterization and evaluation of ceramic properties of clay used in structural ceramics

    International Nuclear Information System (INIS)

    Reis, A.S.; Oliveira, J.N.; Della-Sagrillo, V.P.; Valenzuela-Diaz, F.R.

    2014-01-01

    The clay used in the manufacture of structural ceramic products must meet quality requirements that are influenced by their chemical, physical, mineralogical and microstructural characteristics, which control the ceramic properties of the final products. This paper aims to characterize the clay used in the manufacture of ceramic roof tiles and bricks. The clay was characterized through XRF, XRD, thermogravimetry and differential thermal analysis, Atterberg limits and particle size distribution. Specimens were shaped, dried at 110°C, and burned at 900 deg C in an industrial kiln. After that, they were submitted to tests of water absorption, apparent porosity, bulk density and flexural strength. The results show that the chemical composition of clay has significant amount of silica and alumina and adequate levels of kaolinite for use in structural ceramic. The ceramic properties evaluated in the specimens partially meet the requirements of the Brazilian standard-clays for structural ceramics. (author)

  12. Structural studies of ceramic superconductors

    International Nuclear Information System (INIS)

    Hessel Andersen, N.

    1993-12-01

    The structural and superconducting properties of high temperature superconductors have been studied experimentally and by computer simulation technique. The oxygen ordering in the CuO x basal plane of the high temperature superconductor YBa 2 Cu 3 O 6+x has been studied by Monte Carlo computer simulation based on the socalled ASYNNNI model (Asymmetric Next Nearest Neighbor Interaction model), and the formation of specific domains of the two orthorhombic ordered oxygen phases, Ortho-I and Ortho-II, as function of the oxygen stoichiometry, x, has been related to the superconducting transition temperature, T c (x), via a Minimal Model. A similar relation has been established between the temporal variation of T c (t) and structural oxygen ordering during relaxation following a quench from high temperatures. By neutron diffraction studies on single crystalline YBa 2 Cu 3 O 6.4 the presence of short range domains of the Ortho-II type structure has been established, and the degree of ordering has been found to scale with the observed T c according to the expectations from the established Minimal Model. From neutron diffraction studies on Pb 2 Sr 2 Re 1-x Cu 3 O 8 (RE=Y and Ho) the transition from non-superconducting to superconducting samples with increasing Ca-stoichiometry has been related to the change in the Cu bond valence in the superconducting CuO 2 -planes. X-ray diffraction with Euler four-circle technique and TEM (Transmission Electron Microscopy) have been used to identify structural defects in epitaxial YBa 2 Cu 3 O 6+x thin films produced on MgO (1 0 0) and SrTiO 3 (1 0 0) substrates by laser ablation. The results supply an explanation for the differences in the observed critical current densities, and may be used for optimizing the film production process. A computer-controlled gasvolumetric and a gas-mixing flow system for sample preparation of high temperature superconductors, and studies of oxygen equilibrium pressure and bulk oxygen diffusion have been

  13. Functionally Graded Materials using Plasma Spray with Nano Structured Ceramic

    International Nuclear Information System (INIS)

    Sioh, E L; Tok, A I Y

    2013-01-01

    In this paper, nano structured FGM was fabricated using DC plasma spray technique. Nano structured and micro structured powder were used as the feeding powder with steel substrate. The spray parameters was optimized and characterisation of nano-ceramic FGM and micro-ceramic FGM were done using bending test and micro-hardness test. Experimental results have shown that the nano-structured FGM exhibit 20% improvement flexure strength and 10% in hardness. A comparison was made between sintered micro ceramic tile and nano ceramic FGM using simple drop test method.

  14. Topological design of all-ceramic dental bridges for enhancing fracture resistance.

    Science.gov (United States)

    Zhang, Zhongpu; Chen, Junning; Li, Eric; Li, Wei; Swain, Michael; Li, Qing

    2016-06-01

    Layered all-ceramic systems have been increasingly adopted in major dental prostheses. However, ceramics are inherently brittle, and they often subject to premature failure under high occlusion forces especially in the posterior region. This study aimed to develop mechanically sound novel topological designs for all-ceramic dental bridges by minimizing the fracture incidence under given loading conditions. A bi-directional evolutionary structural optimization (BESO) technique is implemented within the extended finite element method (XFEM) framework. Extended finite element method allows modeling crack initiation and propagation inside all-ceramic restoration systems. Following this, BESO searches the optimum distribution of two different ceramic materials, namely porcelain and zirconia, for minimizing fracture incidence. A performance index, as per a ratio of peak tensile stress to material strength, is used as a design objective. In this study, the novel XFEM based BESO topology optimization significantly improved structural strength by minimizing performance index for suppressing fracture incidence in the structures. As expected, the fracture resistance and factor of safety of fixed partial dentures structure increased upon redistributing zirconia and porcelain in the optimal topological configuration. Dental CAD/CAM systems and the emerging 3D printing technology were commercially available to facilitate implementation of such a computational design, exhibiting considerable potential for clinical application in the future. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

  15. Structural transformation of Nb containing glass - ceramics at thermal treatment

    International Nuclear Information System (INIS)

    Pelss, J.; Misnovs, A.; Berzina, L.; Cimdins, R.; Bossert, J.

    2004-01-01

    Full text: Niobium glass ceramics is know as biomaterial in medicine: stomatology, maxillofacial surgery. The material structure and phase amount influenced on chemical and biological activity of glass-ceramics. Samples from glass powder in system NaO: CaO: Nb 2 O 5 : P 2 O 5 treated at different temperatures (750-1050 0 C) and at different time - from 1 to 6 hours. The glass - ceramics structure investigated by DTA, X-ray and SEM methods

  16. Carbon glass-ceramics and their radiation resistance

    International Nuclear Information System (INIS)

    Virgil'ev, Yu. S.

    1995-01-01

    Structural carbon materials (SCMs) hold great promise for use in numerous plasma-facing components of fusion reactors. One possible candidate for this use is carbon glass-ceramic. Therefore, it is not surprising that there is considerable interest in studying its properties and their variations upon exposure to different radiations, such as neutrons, high-energy electrons, and light ions (H + , D + , and He + ). Here, the authors summarize data accumulated to date on the structure and properties of commercial carbon glass-ceramics and their behavior under irradiation with neutrons, electrons, and some ions

  17. ANL-1(A) - Development of nondestructive evaluation methods for structural ceramics

    International Nuclear Information System (INIS)

    Ellingson, W.A.; Roberts, R.A.; Gopalsami, N.; Dieckman, S.; Hentea, T.; Vaitekunas, J.J.

    1989-01-01

    This section includes the following papers: Development of Nondestructive Evaluation Methods for Structural Ceramics; Effects of Flaws on the Fracture Behavior of Structural Ceramics; Design, Fabrication, and Interface Characterization of Ceramic Fiber-Ceramic Matrix Composites; Development of Advanced Fiber-Reinforced Ceramics; Modeling of Fibrous Preforms for CVD Infiltration; NDT of Advanced Ceramic Composite Materials; Joining of Silicon Carbide Reinforced Ceramics; Superconducting Film Fabrication Research; Short Fiber Reinforced Structural Ceramics; Structural Reliability and Damage Tolerance of Ceramic Composites for High-Temperature Applications; Fabrication of Ceramic Fiber-Ceramic Matrix Composites by Chemical Vapor Infiltration; Characterization of Fiber-CVD Matrix interfacial Bonds; Microwave Sintering of Superconducting Ceramics; Improved Ceramic Composites Through Controlled Fiber-Matrix Interactions; Evaluation of Candidate Materials for Solid Oxide Fuel Cells; Ceramic Catalyst Materials: Hydrous Metal Oxide Ion-Exchange Supports for Coal Liquefaction; and Investigation of Properties and Performance of Ceramic Composite Components

  18. Fire resistance properties of ceramic wool fiber reinforced intumescent coatings

    Energy Technology Data Exchange (ETDEWEB)

    Amir, N., E-mail: norlailiamir@petronas.com.my; Othman, W. M. S. W., E-mail: wamosa@gmail.com; Ahmad, F., E-mail: faizahmad@petronas.com.my [Mechanical Engineering Department, Universiti Teknologi PETRONAS Bandar Seri Iskandar, 31750 Tronoh, Perak (Malaysia)

    2015-07-22

    This research studied the effects of varied weight percentage and length of ceramic wool fiber (CWF) reinforcement to fire retardant performance of epoxy-based intumescent coating. Ten formulations were developed using ammonium polyphosphate (APP), expandable graphite (EG), melamine (MEL) and boric acid (BA). The mixing was conducted in two stages; powdered materials were grinded in Rocklabs mortar grinder and epoxy-mixed using Caframo mixer at low speed mixing. The samples were applied on mild steel substrate and exposed to 500°C heat inside Carbolite electric furnace. The char expansion and its physical properties were observed. Scanning electron microscopy (SEM) analyses were conducted to inspect the fiber dispersion, fiber condition and the cell structure of both coatings and chars produced. Thermogravimetric analyses (TGA) were conducted to study the thermal properties of the coating such as degradation temperature and residual weight. Fire retardant performance was determined by measuring backside temperature of substrate in 1-hour, 1000°C Bunsen burner test according to UL 1709 fire regime. The results showed that intumescent coating reinforced with CWF produced better fire resistance performance. When compared to unreinforced coating, formulation S6-15 significantly reduced steel temperature at approximately 34.7% to around 175°C. However, higher fiber weight percentage had slightly decreased fire retardant performance of the coating.

  19. Fire resistance properties of ceramic wool fiber reinforced intumescent coatings

    Science.gov (United States)

    Amir, N.; Othman, W. M. S. W.; Ahmad, F.

    2015-07-01

    This research studied the effects of varied weight percentage and length of ceramic wool fiber (CWF) reinforcement to fire retardant performance of epoxy-based intumescent coating. Ten formulations were developed using ammonium polyphosphate (APP), expandable graphite (EG), melamine (MEL) and boric acid (BA). The mixing was conducted in two stages; powdered materials were grinded in Rocklabs mortar grinder and epoxy-mixed using Caframo mixer at low speed mixing. The samples were applied on mild steel substrate and exposed to 500°C heat inside Carbolite electric furnace. The char expansion and its physical properties were observed. Scanning electron microscopy (SEM) analyses were conducted to inspect the fiber dispersion, fiber condition and the cell structure of both coatings and chars produced. Thermogravimetric analyses (TGA) were conducted to study the thermal properties of the coating such as degradation temperature and residual weight. Fire retardant performance was determined by measuring backside temperature of substrate in 1-hour, 1000°C Bunsen burner test according to UL 1709 fire regime. The results showed that intumescent coating reinforced with CWF produced better fire resistance performance. When compared to unreinforced coating, formulation S6-15 significantly reduced steel temperature at approximately 34.7% to around 175°C. However, higher fiber weight percentage had slightly decreased fire retardant performance of the coating.

  20. Effects of irradiation on structural properties of crystalline ceramics

    International Nuclear Information System (INIS)

    Clinard, F.W. Jr.; Hurley, G.F.

    1979-01-01

    Stability of crystalline ceramic nuclear waste may be degraded by self-irradiation damage. Changes in density, strength, thermal conductivity, and lattice structure are of concern. Structural damage of ceramics under various radiation conditions is discussed and related to possible effects in nuclear waste

  1. Effects of irradiation on structural properties of crystalline ceramics

    International Nuclear Information System (INIS)

    Clinard, F.W. Jr.; Hurley, G.F.

    1979-01-01

    Stability of crystalline ceramic nuclear waste may be degraded by self-irradiation damage. Changes in density, strength, thermal conductivity, and lattice structure are of concern. In this paper, structural damage of ceramics under various radiation conditions is discussed and related to possible effects in nuclear waste

  2. The fracture resistance of a CAD/CAM Resin Nano Ceramic (RNC) and a CAD ceramic at different thicknesses

    NARCIS (Netherlands)

    Chen, C.; Trindade, F.Z.; de Jager, N.; Kleverlaan, C.J.; Feilzer, A.J.

    2014-01-01

    Objectives This study aimed to investigate the influence of restoration thickness to the fracture resistance of adhesively bonded Lava™ Ultimate CAD/CAM, a Resin Nano Ceramic (RNC), and IPS e.max CAD ceramic. Methods Polished Lava™ Ultimate CAD/CAM (Group L), sandblasted Lava™ Ultimate CAD/CAM

  3. Ceramic Replaces Metal In High Performance Optomechanical Structures

    Science.gov (United States)

    Vasquez, Peter; Fox, Robert L.; Sandford, Stephen P.

    1995-01-01

    Recently developed ceramic materials and fabrication techniques integrated by Langley Research Center workers to produce superior optomechanical structures for spacecraft and aircraft instrumentation. Basic features of these novel supports, such as dimensional stability, low cost, and ease of fabrication, also make them ideal for many commerical optical systems as well. Ceramic supports for optical components and benches offer important advantages over usual metal parts. Ceramic materials expand and contract only slightly with changes in temperature. Moreover, they are relatively inexpensive and lightweight.

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

    Directory of Open Access Journals (Sweden)

    D. Belavic

    2012-04-01

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

  5. Flight-vehicle materials, structures, and dynamics - Assessment and future directions. Vol. 3 - Ceramics and ceramic-matrix composites

    Science.gov (United States)

    Levine, Stanley R. (Editor)

    1992-01-01

    The present volume discusses ceramics and ceramic-matrix composites in prospective aerospace systems, monolithic ceramics, transformation-toughened and whisker-reinforced ceramic composites, glass-ceramic matrix composites, reaction-bonded Si3N4 and SiC composites, and chemical vapor-infiltrated composites. Also discussed are the sol-gel-processing of ceramic composites, the fabrication and properties of fiber-reinforced ceramic composites with directed metal oxidation, the fracture behavior of ceramic-matrix composites (CMCs), the fatigue of fiber-reinforced CMCs, creep and rupture of CMCs, structural design methodologies for ceramic-based materials systems, the joining of ceramics and CMCs, and carbon-carbon composites.

  6. Performance characteristics of porous alumina ceramic structures

    International Nuclear Information System (INIS)

    Latella, B.A.; Liu, T.

    2000-01-01

    Porous ceramics have found a wide range of applications as filters for liquids and gases. The suitability of materials for use in these types of applications depends on the microstructure (grain size, pore size and pore volume fraction) and hence the mechanical and thermal properties. In this study alumina ceramics with different levels of porosity and controlled pore sizes were fabricated and the surface damage and fracture properties were examined. Copyright (2000) The Australian Ceramic Society

  7. A wear-resistant zirconia ceramic for low friction application

    International Nuclear Information System (INIS)

    Winnubst, A.J.A.; Ran, S.; Wiratha, K.W.; Blank, D.H.A.; Pasaribu, H.R.; Sloetjes, J.W.; Schipper, D.J.

    2004-01-01

    A high wear-resistant ceramic/ceramic couple is described associated with low friction. By adding a small amount CuO to yttria-doped tetragonal zirconia (Y-TZP) the (dry) coefficient of friction against alumina is only 0.2 during a sliding distance of 3-5 km after which the coefficient drastically increases and a transition from mild to sever wear occurs. Pure Y-TZP exhibits a coefficient of friction of 0.7 under the same experimental conditions but wear remains mild during the test (upto 10 km of sliding distance). These small amounts of CuO also strongly influence the densification behaviour. Sintering of this system occurs in several steps where among other things dissolution of CuO in the Y-TZP matrix as well as liquid phase sintering takes place. Non-uniform shrinkage of the CuO-doped system resulting in relative large microcracks in the ceramic can explain its sudden drastic increase in coefficient of friction and wear rate after 3-5 km of operation. (orig.)

  8. Ballistic Impact Simulation of Ceramic/Metal Armor Structures

    OpenAIRE

    ARSLAN, Kemal; GÜNEŞ, Recep

    2017-01-01

    The study presents a comparative numericalinvestigation on ballistic performance of ceramic/metal armor structures. 2Daxisymmetric numerical model was developed for ballistic impact simulationsusing LS-DYNA® finite element software. The armor structuresincluded combinations of boron carbide (B4C), Al6061-T6 and 4340steel constituents. The interfaces in the armor structure were modelled with anepoxy resin adhesive. In order to define proper material behavior,Johnson-Holmquist-Ceramics material...

  9. Structure and multiferroic properties of barium hexaferrite ceramics

    International Nuclear Information System (INIS)

    Tan, Guolong; Chen, Xiuna

    2013-01-01

    Simultaneous occurrence of large ferroelectricity and strong ferromagnetism have been observed in barium hexaferrite ceramics. Barium hexaferrite (BaFe 12 O 19 ) powders with hexagonal crystal structure were successfully synthesized in a polymer precursor method using barium acetate and ferric acetylacetonate as the precursors. The powders were pressed into pellets which were sintered into ceramics at 1200 °C and 1300 °C for 1 h. The structure and morphology of the ceramics were examined using X-ray diffraction and field emission scanning electron microscopy. Large spontaneous polarization was observed in the BaFe 12 O 19 ceramics at room temperature, revealing a clear ferroelectric hysteresis loop. The maximum remanent polarization of the BaFe 12 O 19 ceramic was estimated approximately 11.8 μC cm −2 . The FeO 6 octahedron in its perovskite-like hexagonal unit cell and the shift of Fe 3+ off the center of octahedron are suggested to be the origin of the polarization in BaFe 12 O 19 . The BaFe 12 O 19 ceramics also showed strong ferromagnetism at room temperature. - Graphical abstract: Ferroelectric hysteresis loops of BaFe 12 O 19 ceramics measured at a frequency of 120 Hz, which shows that the ceramics sintered at 1200 °C is ferroelectric with P r ∼11.8 μC/cm 2 . Highlights: ► Large ferroelectricity and strong ferromagnetism were observed in barium hexaferrite ceramics. ► The maximum remanent polarization of the BaFe 12 O 19 ceramic was estimated to be 11.8 μC cm −2 . ► The FeO 6 octahedron and off-center shift of Fe 3+ are suggested to be the origin of the polarization.

  10. Erosion resistance and adhesion of composite metal/ceramic coatings produced by plasma spraying

    International Nuclear Information System (INIS)

    Ramm, D.A.J.; Hutchings, I.M.; Clyne, T.W.

    1993-01-01

    Ceramic coatings can exhibit greater erosion resistance than most metallic coatings. Such coatings are conveniently produced by thermal spraying. Unfortunately, thermally sprayed ceramic coatings often exhibit poor adhesion, partly as a consequence of the development of residual stresses during spraying and subsequent cooling. Composite coatings have been studied using aluminium/alumina deposits on steel substrates. The incorporation of ceramics within a ductile matrix has potential for sharply reducing the erosive wear at high erodent impact angles, whilst retaining the good erosion resistance of ceramics at low angles. It is shown that the proportion of metal and ceramic at the free surface can be specified so as to optimise the erosion resistance. Experiments have also been carried out on the resistance of the coatings to debonding during four-point bending of the coated substrate. Progress is being made towards the tailoring of composition profiles in graded coatings so as to optimise the combination of erosion resistance and adhesion. (orig.)

  11. "A New Class of Creep Resistant Oxide/Oxide Ceramic Matrix Composites"

    Energy Technology Data Exchange (ETDEWEB)

    Dr. Mohit Jain, Dr. Ganesh Skandan, Prof. Roger Cannon, Rutgers University

    2007-03-30

    Despite recent progress in the development of SiC-SiC ceramic matrix composites (CMCs), their application in industrial gas turbines for distributed energy (DE) systems has been limited. The poor oxidation resistance of the non-oxide ceramics warrants the use of envrionmental barrier coatings (EBCs), which in turn lead to issues pertaining to life expectancy of the coatings. On the other hand, oxide/oxide CMCs are potential replacements, but their use has been limited until now due to the poor creep resistance at high temperatures, particularly above 1200 oC: the lack of a creep resistant matrix has been a major limiting factor. Using yttrium aluminum garnet (YAG) as the matrix material system, we have advanced the state-of-the-art in oxide/oxide CMCs by introducing innovations in both the structure and composition of the matrix material, thereby leading to high temperature matrix creep properties not achieved until now. An array of YAG-based powders with a unique set of particle characteristics were produced in-house and sintered to full density and compressive creep data was obtained. Aided in part by the composition and the microstructure, the creep rates were found to be two orders of magnitude smaller than the most creep resistant oxide fiber available commercially. Even after accounting for porosity and a smaller matrix grain size in a practical CMC component, the YAG-based matrix material was found to creep slower than the most creep resistant oxide fiber available commercially.

  12. Resonator structures on AlN ceramics surface treated by laser radiation

    Science.gov (United States)

    Koziol, Pawel E.; Antonczak, Arkadiusz J.; Stepak, Bogusz; Gorski, Przemyslaw A.; Walczakowski, Michal; Palka, Norbert; Abramski, Krzysztof M.

    2014-03-01

    In this paper a method for producing resonant structures using laser micromachining is presented. In the spot of laser beam impact on AlN ceramics surface a conductive aluminum layer is formed. Compilation of process parameters allows for the fabrication of structures with resistance at Rs ~ 0.01Ω/Rs. It has been also found out that the maximum value of resistance for which spiral resonator structures manifest their unique properties is at the level of Rs = 1.43 Ω. Furthermore, the occurrence of mutual capacity which value is dependent on the arrangement of individual SR structures with respect to each other was observed and examined. Based on satisfactory results for SR structures, it has been attempted to produce a resonant structures dedicated to the THz range based on the process of direct metallization of AlN ceramics surface. As a result, the Split Ring Resonator structure whose properties were verified by using the THz -TDS method was manufactured. In case of the field E perpendicular to SRR structure and one resonance area for 0.50 THz with field E parallel to the structure, two characteristic resonant dips for 0.22 THz and 0.46 THz were obtained. The studies confirmed that the method of direct metallization of AlN ceramics allows to produce resonant structures in the THz range.

  13. Ceramic ware waste as coarse aggregate for structural concrete production.

    Science.gov (United States)

    García-González, Julia; Rodríguez-Robles, Desirée; Juan-Valdés, Andrés; Morán-Del Pozo, Julia M; Guerra-Romero, M Ignacio

    2015-01-01

    The manufacture of any kind of product inevitably entails the production of waste. The quantity of waste generated by the ceramic industry, a very important sector in Spain, is between 5% and 8% of the final output and it is therefore necessary to find an effective waste recovery method. The aim of the study reported in the present article was to seek a sustainable means of managing waste from the ceramic industry through the incorporation of this type of waste in the total replacement of conventional aggregate (gravel) used in structural concrete. Having verified that the recycled ceramic aggregates met all the technical requirements imposed by current Spanish legislation, established in the Code on Structural Concrete (EHE-08), then it is prepared a control concrete mix and the recycled concrete mix using 100% recycled ceramic aggregate instead of coarse natural aggregate. The concretes obtained were subjected to the appropriate tests in order to conduct a comparison of their mechanical properties. The results show that the concretes made using ceramic sanitary ware aggregate possessed the same mechanical properties as those made with conventional aggregate. It is therefore possible to conclude that the reuse of recycled ceramic aggregate to produce recycled concrete is a feasible alternative for the sustainable management of this waste.

  14. Evaluation of mechanical properties and structural changes of ceramic filter materials for hot gas cleaning under simulated process conditions

    OpenAIRE

    Westerheide, R.; Wehd, C. von der; Rehak, P.; Adler, J.

    2002-01-01

    In the combined cycle technology for advanced coal fired power plants at high temperatures up to 950 °C the removal of particles from the stream to the gas turbine is carried out with ceramic filter elements. These elements consist often of siliceous bonded coarse grained silicon carbide. A stable long term operation of the filter elements leads to the demands on good resistance towards thermal, mechanical and chemical loading. The structure of ceramic filter elements consists usually of a hi...

  15. Erosion resistance and adhesion of composite metal/ceramic coatings produced by plasma spraying

    OpenAIRE

    Ramm , D.; Hutchings , I.; Clyne , T.

    1993-01-01

    Ceramic coatings can exhibit greater erosion resistance than most metallic coatings. Such coatings are conveniently produced by thermal spraying. Unfortunately, thermally sprayed ceramic coatings often exhibit poor adhesion, partly as a consequence of the development of residual stresses during spraying and subsequent cooling. Composite coatings have been studied using aluminium/alumina deposits on steel substrates. The incorporation of ceramics within a ductile matrix has potential for sharp...

  16. Mechanistic Studies of Superplasticity of Structural Ceramics

    Science.gov (United States)

    1992-02-01

    powder suspension, and direct consolida- gy and, correspondingly, strengthening tion of the slurry into a green body using the grain boundary. colloidal...librium, must possess a countercharge which is negative (posi- trolyte. The milled slurry was cast, under a pressure of up to tive). The dopants, in...34Space Charges, Elastic CeO2 -ZrO 2" pp. 147-52 in Materials Science Forum, Vol. 34-36, Ceramic Field and Dipole Contributions to Equilibrium Solute

  17. Structural properties and neutron irradiation effects of ceramics

    International Nuclear Information System (INIS)

    Yano, Toyohiko

    1994-01-01

    In high temperature gas-cooled reactors and nuclear fusion reactors being developed at present, various ceramics are to be used in the environment of neutron irradiation for undertaking important functions. The change of the characteristics of those materials by neutron irradiation must be exactly forecast, but it has been known that the response of the materials is different respectively. The production method of ceramics and the resulted structures of ceramics which control their characteristics are explained. The features of covalent bond and ionic bond, the synthesis of powder and the phase change by heating, sintering and sintering agent, and grain boundary phase are described. The smelling of ceramics by neutron irradiation is caused by the formation of the clusters of Frenkel defects and minute spot defects. Its restoration by annealing is explained. The defects remaining in materials after irradiation are the physical defects by flipping atoms cut due to the collision with high energy particles and the chemical defects by nuclear transformation. Some physical defects can be restored, but chemical defects are never restored. The mechanical properties of ceramics and the effect of irradiation on them, and the thermal properties of ceramics and the effect of irradiation on them are reported. (K.I.)

  18. Printed sub-100 nm polymer-derived ceramic structures.

    Science.gov (United States)

    Duong, Binh; Gangopadhyay, Palash; Brent, Josh; Seraphin, Supapan; Loutfy, Raouf O; Peyghambarian, Nasser; Thomas, Jayan

    2013-05-01

    We proposed an unconventional fabrication technique called spin-on nanoprinting (SNAP) to generate and transfer sub-100 nm preceramic polymer patterns onto flexible and rigid substrates. The dimensions of printed nanostructures are almost the same as those of the mold, since the ceramic precursor used is a liquid. The printed patterns can be used as a replica for printing second-generation structures using other polymeric materials or they can be further converted to desirable ceramic structures, which are very attractive for high-temperature and harsh environment applications. SNAP is an inexpensive parallel process and requires no special equipment for operation.

  19. Preparation, structure and dielectric property of barium stannate titanate ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Wei Xiaoyong [Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education, Xi' an Jiaotong Univesity, Xi' an 710049 (China)]. E-mail: wdy@mail.xjtu.edu.cn; Yao Xi [Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education, Xi' an Jiaotong Univesity, Xi' an 710049 (China)

    2007-02-25

    The processing route of barium stannate titanate ceramics were optimized to prepare full composition range solid solution sample. The phase structure, microscopic morphology and dielectric properties of barium stannate titanate ceramics were studied. X-ray diffraction patterns indicated that the samples are of single perovskite structure. Linear empirical relationship between crystal lattice and tin content was proposed. This relationship is valid covering the full composition range, which suggests that this solid solution system is ultimate mutual soluble. The phase transition behavior was studied and a phase diagram was obtained based on the dielectric measurements.

  20. Vacuum tight sodium resistant compound between ThO2 ceramic and metal

    International Nuclear Information System (INIS)

    Reetz, T.

    A method for evaluating the mechanical tensions for metal/ ceramic joinings was applied to the selection of metal components for a highly vacuum tight, sodium-resistant metal/ThO 2 ceramic solder joining. The metal component selected was the iron--nickel alloy Dilasil which is joined to the ceramic using a nickel-based solder. The wetting of the cearamic could be carried out using the titanium hydride technique or after the formation of a W-cerium layer on the surface of this ceramic. (U.S.)

  1. Electrostatic Assembly Preparation of High-Toughness Zirconium Diboride-Based Ceramic Composites with Enhanced Thermal Shock Resistance Performance.

    Science.gov (United States)

    Zhang, Baoxi; Zhang, Xinghong; Hong, Changqing; Qiu, Yunfeng; Zhang, Jia; Han, Jiecai; Hu, PingAn

    2016-05-11

    The central problem of using ceramic as a structural material is its brittleness, which associated with rigid covalent or ionic bonds. Whiskers or fibers of strong ceramics such as silicon carbide (SiC) or silicon nitride (Si3N4) are widely embedded in a ceramic matrix to improve the strength and toughness. The incorporation of these insulating fillers can impede the thermal flow in ceramic matrix, thus decrease its thermal shock resistance that is required in some practical applications. Here we demonstrate that the toughness and thermal shock resistance of zirconium diboride (ZrB2)/SiC composites can be improved simultaneously by introducing graphene into composites via electrostatic assembly and subsequent sintering treatment. The incorporated graphene creates weak interfaces of grain boundaries (GBs) and optimal thermal conductance paths inside composites. In comparison to pristine ZrB2-SiC composites, the toughness of (2.0%) ZrB2-SiC/graphene composites exhibited a 61% increasing (from 4.3 to 6.93 MPa·m(1/2)) after spark plasma sintering (SPS); the retained strength after thermal shock increased as high as 74.8% at 400 °C and 304.4% at 500 °C. Present work presents an important guideline for producing high-toughness ceramic-based composites with enhanced thermal shock properties.

  2. Structure recognition from high resolution images of ceramic composites

    Energy Technology Data Exchange (ETDEWEB)

    Ushizima, Daniela; Perciano, Talita; Krishnan, Harinarayan; Loring, Burlen; Bale, Hrishikesh; Parkinson, Dilworth; Sethian, James

    2015-01-05

    Fibers provide exceptional strength-to-weight ratio capabilities when woven into ceramic composites, transforming them into materials with exceptional resistance to high temperature, and high strength combined with improved fracture toughness. Microcracks are inevitable when the material is under strain, which can be imaged using synchrotron X-ray computed micro-tomography (mu-CT) for assessment of material mechanical toughness variation. An important part of this analysis is to recognize fibrillar features. This paper presents algorithms for detecting and quantifying composite cracks and fiber breaks from high-resolution image stacks. First, we propose recognition algorithms to identify the different structures of the composite, including matrix cracks and fibers breaks. Second, we introduce our package F3D for fast filtering of large 3D imagery, implemented in OpenCL to take advantage of graphic cards. Results show that our algorithms automatically identify micro-damage and that the GPU-based implementation introduced here takes minutes, being 17x faster than similar tools on a typical image file.

  3. The influence of veneering porcelain thickness of all-ceramic and metal ceramic crowns on failure resistance after cyclic loading.

    Science.gov (United States)

    Shirakura, Akihiko; Lee, Heeje; Geminiani, Alessandro; Ercoli, Carlo; Feng, Changyong

    2009-02-01

    In some clinical situations, the length of either a prepared tooth or an implant abutment is shorter than ideal, and the thickness of a porcelain crown must be increased. Thickness of the coping and the veneering porcelain should be considered to prevent mechanical failure of the crown. The purpose of this study was to investigate the influence of veneering porcelain thickness for all-ceramic and metal ceramic crowns on failure resistance after cyclic loading. All-ceramic and metal ceramic crowns (n=20) were fabricated on an implant abutment (RN Solid Abutment) for the study. Two different framework designs with 2 different incisal thicknesses of veneering porcelain (2 mm and 4 mm) were used for each all-ceramic and metal ceramic crown system, resulting in 4 experimental groups (n=10) with identically shaped crowns. The all-ceramic crown consisted of alumina (Procera AllCeram) frameworks and veneering porcelain (Cerabien), while metal ceramic crowns were made of high noble metal (Leo) frameworks and veneering porcelain (IPS Classic). All crowns were cemented on the corresponding abutments using a resin cement (Panavia 21). They were subjected to 1000 cycles of thermal cycling (5 degrees C and 55 degrees C; 5-second dwell time). The crowns were tested with a custom-designed cyclic loading apparatus which delivered simultaneous unidirectional cyclic loading at 135 degrees, vertically, at an rpm of 250, with a load of 49 N. Each specimen was loaded for 1.2 x 106 cycles or until it failed. The specimens were thoroughly evaluated for cracks and/or bulk fracture with an optical stereomicroscope (x10) and assigned a score of success, survival, or failure. The specimens without bulk fracture after cyclic loading were loaded along the long axis of the tooth, on the incisal edge, in a universal testing machine at a crosshead speed of 1.5 mm/min, until fracture. Fisher's exact test was used to compare the success and survival rate between the 2 different materials (alpha=.05

  4. Contact Resistance of Ceramic Interfaces Between Materials Used for Solid Oxide Fuel Cell Applications

    DEFF Research Database (Denmark)

    Koch, Søren

    The contact resistance can be divided into two main contributions. The small area of contact between ceramic components results in resistance due to current constriction. Resistive phases or potential barriers at the interface result in an interface contribution to the contact resistance, which may...... be smaller or larger than the constriction resistance. The contact resistance between pairs of three different materials were analysed (stron-tium doped lanthanum manganite, yttria stabilised zirconia and strontium and nickel doped lanthanum cobaltite), and the effects of temperature, atmosphere......, polarisation and mechanical load on the contact resistance were investigated. The investigations revealed that the mechanical load of a ceramic contact has a high influence on the contact resistance, and generally power law dependence between the contact resistance and the mechanical load was found...

  5. Chipping Resistance of Graded Zirconia Ceramics for Dental Crowns

    Science.gov (United States)

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

    2012-01-01

    A serious drawback of veneering porcelains is a pronounced susceptibility to chipping. Glass-infiltrated dense zirconia structures can now be produced with esthetic quality, making them an attractive alternative. In this study, we examined the hypothesis that such infiltrated structures are much more chip-resistant than conventional porcelains, and at least as chip-resistant as non-infiltrated zirconia. A sharp indenter was used to produce chips in flat and anatomically correct glass-infiltrated zirconia crown materials, and critical loads were measured as a function of distance from the specimen edge (flat) or side wall (crown). Control data were obtained on zirconia specimens without infiltration and on crowns veneered with porcelains. The results confirmed that the resistance to chipping in graded zirconia is more than 4 times higher than that of porcelain-veneered zirconia and is at least as high as that of non-veneered zirconia. PMID:22232142

  6. Influence of electrical resistivity and machining parameters on electrical discharge machining performance of engineering ceramics.

    Science.gov (United States)

    Ji, Renjie; Liu, Yonghong; Diao, Ruiqiang; Xu, Chenchen; Li, Xiaopeng; Cai, Baoping; Zhang, Yanzhen

    2014-01-01

    Engineering ceramics have been widely used in modern industry for their excellent physical and mechanical properties, and they are difficult to machine owing to their high hardness and brittleness. Electrical discharge machining (EDM) is the appropriate process for machining engineering ceramics provided they are electrically conducting. However, the electrical resistivity of the popular engineering ceramics is higher, and there has been no research on the relationship between the EDM parameters and the electrical resistivity of the engineering ceramics. This paper investigates the effects of the electrical resistivity and EDM parameters such as tool polarity, pulse interval, and electrode material, on the ZnO/Al2O3 ceramic's EDM performance, in terms of the material removal rate (MRR), electrode wear ratio (EWR), and surface roughness (SR). The results show that the electrical resistivity and the EDM parameters have the great influence on the EDM performance. The ZnO/Al2O3 ceramic with the electrical resistivity up to 3410 Ω·cm can be effectively machined by EDM with the copper electrode, the negative tool polarity, and the shorter pulse interval. Under most machining conditions, the MRR increases, and the SR decreases with the decrease of electrical resistivity. Moreover, the tool polarity, and pulse interval affect the EWR, respectively, and the electrical resistivity and electrode material have a combined effect on the EWR. Furthermore, the EDM performance of ZnO/Al2O3 ceramic with the electrical resistivity higher than 687 Ω·cm is obviously different from that with the electrical resistivity lower than 687 Ω·cm, when the electrode material changes. The microstructure character analysis of the machined ZnO/Al2O3 ceramic surface shows that the ZnO/Al2O3 ceramic is removed by melting, evaporation and thermal spalling, and the material from the working fluid and the graphite electrode can transfer to the workpiece surface during electrical discharge

  7. Influence of Electrical Resistivity and Machining Parameters on Electrical Discharge Machining Performance of Engineering Ceramics

    Science.gov (United States)

    Ji, Renjie; Liu, Yonghong; Diao, Ruiqiang; Xu, Chenchen; Li, Xiaopeng; Cai, Baoping; Zhang, Yanzhen

    2014-01-01

    Engineering ceramics have been widely used in modern industry for their excellent physical and mechanical properties, and they are difficult to machine owing to their high hardness and brittleness. Electrical discharge machining (EDM) is the appropriate process for machining engineering ceramics provided they are electrically conducting. However, the electrical resistivity of the popular engineering ceramics is higher, and there has been no research on the relationship between the EDM parameters and the electrical resistivity of the engineering ceramics. This paper investigates the effects of the electrical resistivity and EDM parameters such as tool polarity, pulse interval, and electrode material, on the ZnO/Al2O3 ceramic's EDM performance, in terms of the material removal rate (MRR), electrode wear ratio (EWR), and surface roughness (SR). The results show that the electrical resistivity and the EDM parameters have the great influence on the EDM performance. The ZnO/Al2O3 ceramic with the electrical resistivity up to 3410 Ω·cm can be effectively machined by EDM with the copper electrode, the negative tool polarity, and the shorter pulse interval. Under most machining conditions, the MRR increases, and the SR decreases with the decrease of electrical resistivity. Moreover, the tool polarity, and pulse interval affect the EWR, respectively, and the electrical resistivity and electrode material have a combined effect on the EWR. Furthermore, the EDM performance of ZnO/Al2O3 ceramic with the electrical resistivity higher than 687 Ω·cm is obviously different from that with the electrical resistivity lower than 687 Ω·cm, when the electrode material changes. The microstructure character analysis of the machined ZnO/Al2O3 ceramic surface shows that the ZnO/Al2O3 ceramic is removed by melting, evaporation and thermal spalling, and the material from the working fluid and the graphite electrode can transfer to the workpiece surface during electrical discharge

  8. Ceramic matrix composites -- Advanced high-temperature structural materials

    International Nuclear Information System (INIS)

    Lowden, R.A.; Ferber, M.K.; DiPietro, S.G.

    1995-01-01

    This symposium on Ceramic Matrix Composites: Advanced High-Temperature Structural Materials was held at the 1994 MRS Fall Meeting in Boston, Massachusetts on November 28--December 2. The symposium was sponsored by the Department of Energy's Office of Industrial Technology's Continuous Fiber Ceramic Composites Program, the Air Force Office of Scientific Research, and NASA Lewis Research Center. Among the competing materials for advanced, high-temperature applications, ceramic matrix composites are leading candidates. The symposium was organized such that papers concerning constituents--fibers and matrices--were presented first, followed by composite processing, modeling of mechanical behavior, and thermomechanical testing. More stable reinforcements are necessary to enhance the performance and life of fiber-reinforced ceramic composites, and to ensure final acceptance of these materials for high-temperature applications. Encouraging results in the areas of polymer-derived SiC fibers and single crystal oxide filaments were given, suggesting composites with improved thermomechanical properties and stability will be realized in the near future. The significance of the fiber-matrix interface in the design and performance of these materials is evident. Numerous mechanical models to relate interface properties to composite behavior, and interpret test methods and data, were enthusiastically discussed. One issue of great concern for any advanced material for use in extreme environments is stability. This theme arose frequently throughout the symposium and was the topic of focus on the final day. Fifty nine papers have been processed separately for inclusion on the data base

  9. FY 1997 report on the study on development of corrosion-resistant ceramics for refuse incinerators; 1997 nendo chosa hokokusho (gomi shokyakuroyo taishoku ceramics zairyo no kaihatsu ni kansuru kenkyu)

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-03-01

    This paper describes development of structural materials for municipal refuse incinerators, in particular, high- temperature corrosion-resistant ceramics for inner walls. Unlike boiler tubes of which inner walls are cooled by water or water vapor, refractory for inner walls is subjected to high-temperature flame over 1000degC, corrosive gases such as HCl and SO2. and low-melting point corrosive dust such as chloride, sulfate and oxide under strong corrosive environment. Experiment was made on 14 kinds of ceramics including commercially available oxide system, non-oxide system and refractory system ceramics. Except graphite system ones, every ceramics, in particular, Al2O3, ZrO2, B4C-doped SiC and CVD-SiO showed superior properties. Commercially available ceramics, in particular, non-oxide system ones are very expensive. Since inner wall materials for refuse incinerators are heat-/corrosion-resistant consumption articles, it is suggested that improvement of reasonable oxide system ceramics or conventional SiC system ones is better. 73 refs., 89 figs., 39 tabs.

  10. Friction in Sliding Orthodontic Mechanics: Ceramic Brackets, Teflon-Coated Wires and Comparative Resistances

    Science.gov (United States)

    1989-01-01

    N Tn FRICTION IN SLIDING ORTHODONTIC MECHANICS: N CERAMIC BRACKETS, TEFLON-COATED WIRES , AND COMPARATIVE RESISTANCES 0 DTICSFLECTED James R. Gill1...obsolete. SECURITY CLASSIFICATION OF THIS PAGE AFIT/CI "OVERPRINT" I FRICTION IN SLIDING ORTHODONTIC MECHANICS: CERAMIC BRACKETS, TEFLON-COATED WIRES ...brackets, arch- wires , and ligations during simulated orthodontic edgewise sliding mechanics. Independent variables and their values were 1) bracket

  11. Comparison of frictional resistance between conventional stainless steel, metal insert ceramic, self ligating stainless steel and self ligating ceramic with stainless steel wire : invitro study

    Directory of Open Access Journals (Sweden)

    Sivaram Subbiah

    2010-01-01

    Full Text Available Friction is an integral part of fixed orthodontic treatment. Several innovations have been made to reduce friction and thereby get predictable and faster tooth movements. Self ligating brackets are one such innovation which is said to offer the possibility of a significant reduction in average treatment times and also in anchorage requirements. Ceramic Self ligating brackets introduce recently have the added advantage of aesthetics. This study was conducted to compare the frictional resistance of conventional stainless steel, metal insert ceramic, Self ligating stainless steel and Self ligating ceramic brackets against a common stainless steel wire. Fifteen premolar in each group (0.022 Roth prescription were tested against 0.019x0.025 stainless steel wire using Lloyd universal testing machine. The conventional stainless steel brackets showed a frictional resistance of 66.47±7.86g metal insert ceramic brackets showed a frictional resistance of 77.52± 8.59g . the Self ligating stainless steel brackets had a frictional resistance of 40.21±7.76g Self ligating ceramic brackets had a frictional resistance of 72.67±5.76 g Self ligating ceramic brackets do have slightly lesser friction than metal insert ceramic brackets but significantly more than metal brackets .

  12. Numerical Simulation for Thermal Shock Resistance of Ultra-High Temperature Ceramics Considering the Effects of Initial Stress Field

    Directory of Open Access Journals (Sweden)

    Weiguo Li

    2011-01-01

    Full Text Available Taking the hafnium diboride ceramic as an example, the effects of heating rate, cooling rate, thermal shock initial temperature, and external constraint on the thermal shock resistance (TSR of ultra-high temperature ceramics (UHTCs were studied through numerical simulation in this paper. The results show that the external constraint has an approximately linear influence on the critical rupture temperature difference of UHTCs. The external constraint prepares a compressive stress field in the structure because of the predefined temperature field, and this compressive stress field relieves the tension stress in the structure when it is cooled down and then it improves the TSR of UHTCs. As the thermal shock initial temperature, a danger heating rate (or cooling rate exists where the critical temperature difference is the lowest.

  13. A new high temperature resistant glass–ceramic coating for gas ...

    Indian Academy of Sciences (India)

    Unknown

    Abstract. A new high temperature and abrasion resistant glass–ceramic coating system (based on MgO–. Al2O3–TiO2 and ZnO–Al2O3–SiO2 based glass systems) for gas turbine engine components has been developed. Thermal shock resistance, adherence at 90°-bend test and static oxidation resistance at the required ...

  14. Bioactive glass–ceramic coating for enhancing the in vitro corrosion resistance of biodegradable Mg alloy

    International Nuclear Information System (INIS)

    Ye Xinyu; Cai Shu; Dou Ying; Xu Guohua; Huang Kai; Ren Mengguo; Wang Xuexin

    2012-01-01

    Highlights: ► Sol–gel derived 45S5 glass–ceramic coating was prepared on Mg alloy substrate. ► The corrosion resistance of glass–ceramic coated Mg alloy was markedly improved. ► The corrosion behavior of the coated sample varied due to the cracking of coating. - Abstract: In this work, a bioactive 45S5 glass–ceramic coating was synthesized on magnesium (Mg) alloy substrate by using a sol–gel dip-coating method, to improve the initial corrosion resistance of AZ31 Mg alloy. The surface morphology and phase composition of the glass–ceramic coating were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The coating composed of amorphous phase and crystalline phase Na 2 Ca 2 Si 3 O 9 , with the thickness of ∼1.0 μm, exhibited a uniform and crack-free surface morphology. The corrosion behavior of the uncoated and coated Mg alloy substrates was investigated by the electrochemical measurements and immersion tests in simulated body fluid (SBF). Potentiodynamic polarization tests recorded an increase of potential (E corr ) form −1.60 V to −1.48 V, and a reduction of corrosion current density (i corr ) from 4.48 μA cm −2 to 0.16 μA cm −2 , due to the protection provided by the glass–ceramic coating. Immersion tests also showed the markedly improved corrosion resistance of the coated sample over the immersion period of 7 days. Moreover, after 14 days of immersion in SBF, the corrosion resistance of the coated sample declined due to the cracking of the glass–ceramic coating, which was confirmed by electrochemical impedance spectroscopy (EIS) analysis. The results suggested that the 45S5 glass–ceramic coated Mg alloy could provide a suitable corrosion behavior for use as degradable implants.

  15. Characterization, Microstructure, and Dielectric properties of cubic pyrochlore structural ceramics

    KAUST Repository

    Li, Yangyang

    2013-05-01

    The (BMN) bulk materials were sintered at 1050°C, 1100°C, 1150°C, 1200°C by the conventional ceramic process, and their microstructure and dielectric properties were investigated by Scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, Transmission electron microscopy (TEM) (including the X-ray energy dispersive spectrometry EDS and high resolution transmission electron microscopy HRTEM) and dielectric impedance analyzer. We systematically investigated the structure, dielectric properties and voltage tunable property of the ceramics prepared at different sintering temperatures. The XRD patterns demonstrated that the synthesized BMN solid solutions had cubic phase pyrochlore-type structure when sintered at 1050°C or higher, and the lattice parameter (a) of the unit cell in BMN solid solution was calculated to be about 10.56Å. The vibrational peaks observed in the Raman spectra of BMN solid solutions also confirmed the cubic phase pyrochlore-type structure of the synthesized BMN. According to the Scanning Electron Microscope (SEM) images, the grain size increased with increasing sintering temperature. Additionally, it was shown that the densities of the BMN ceramic tablets vary with sintering temperature. The calculated theoretical density for the BMN ceramic tablets sintered at different temperatures is about 6.7521 . The density of the respective measured tablets is usually amounting more than 91% and 5 approaching a maximum value of 96.5% for sintering temperature of 1150°C. The microstructure was investigated by using Scanning Transmission Electron Microscope (STEM), X-ray diffraction (XRD). Combined with the results obtained from the STEM and XRD, the impact of sintering temperature on the macroscopic and microscopic structure was discussed. The relative dielectric constant ( ) and dielectric loss ( ) of the BMN solid solutions were measured to be 161-200 and (at room temperature and 100Hz-1MHz), respectively. The BMN solid

  16. Thermal-shock Resistance of a Ceramic Comprising 60 Percent Boron Carbide and 40 Percent Titanium Diboride

    Science.gov (United States)

    Yeomans, C M; Hoffman, C A

    1953-01-01

    Thermal-shock resistance of a ceramic comprising 60 percent boron carbide and 40 percent titanium diboride was investigated. The material has thermal shock resistance comparable to that of NBS body 4811C and that of zirconia, but is inferior to beryllia, alumina, and titanium-carbide ceramals. It is not considered suitable for turbine blades.

  17. Structural analysis of ceramic blocks sealing or structural incorporated with the industrial laundry sludge

    International Nuclear Information System (INIS)

    Almeida, P.H.S.; Grippe, V.Y.Q.; Goulart, J.V.

    2016-01-01

    Industrial and commercial development of recent decades has led to an increase in waste generation. Thus, it is necessary to develop alternative and effective methods of treatment, replacing the simple disposal of these wastes in landfills. The objective of this work is to study the incorporation of textile industrial laundries sludge in ceramic blocks sealing or structural. Samples of ceramic blocks were produced using formulation with 20% sludge, the mass of ceramic clay. Structural analysis of the block was observed the tendency of most empty emergence (pores) during the firing of the blocks, as textile sludge was added in the ceramic paste composition. The mechanical testing of blocks compressive strength was above the minimum 3.0 MPa specified by the standard limit. The physical test water absorption of the blocks was within the range 8 to 22% specified by the standard. (author)

  18. Fabrication of low specific resistance ceramic carbon composites by ...

    Indian Academy of Sciences (India)

    2017-09-07

    Sep 7, 2017 ... C showing resistor behaviour even at low carbon content (1 wt%). In this work, ceramic carbon composites were fabricated using alumina–clay slurries with addition of glucose as a soluble carbon source. Morphology of the sintered samples was characterized by field emission gun (FEG) electron ...

  19. Fabrication of low specific resistance ceramic carbon composites by ...

    Indian Academy of Sciences (India)

    2017-10-15

    Oct 15, 2017 ... In this work, ceramic carboncomposites were fabricated using alumina–clay slurries with addition of glucose as a soluble carbon source. Morphology ofthe sintered samples was characterized by field emission gun (FEG) electron microscopy. Phase analysis was done by X-raydiffraction (XRD). Electrical ...

  20. Fatigue resistance and microleakage of CAD/CAM ceramic and composite molar crowns.

    Science.gov (United States)

    Kassem, Amr S; Atta, Osama; El-Mowafy, Omar

    2012-01-01

    The aim of this study was to determine effect of compressive cyclic loading on fatigue resistance and microleakage of monolithic CAD/CAM molar ceramic and composite crowns. Thirty-two extracted molars were prepared to receive CEREC crowns according to manufacturer's guidelines using a special paralleling device (Parallel-A-Prep). Sixteen feldspathic ceramic crowns (VITABLOCS Mark II) (VMII) and 16 resin-composite crowns (Paradigm-MZ100 blocks) (PMZ) were milled using a CEREC-3D machine. Eight crowns of each group were cemented to their respective teeth using self-etching resin cement (Panavia-F-2.0) (PAN), and eight were cemented using self-adhesive resin cement (RelyX-Unicem-Clicker) (RXU). Following storage for 1 week in water, specimens were subjected to uniaxial compressive cyclic loading in an Instron testing machine at 12 Hz for 1,000,000 cycles. Load was applied at the central fossa, and the cycle range was 60-600 N. Specimens were then subjected to microleakage testing. Data were statistically analyzed using factorial ANOVA and Post Hoc (Tukey HSD) tests. All composite crowns survived compressive cyclic loading without fracture, while three ceramic crowns from the subgroup cemented with RXU developed surface cracks at the center of occlusal surfaces, extending laterally. Microleakage scores of ceramic crowns cemented with PAN were significantly lower than those of the other three subgroups (p crowns were more fatigue-resistant than VMII ceramic crowns. Cement type had a significant effect on fatigue resistance of the ceramic crowns but not the composite ones. Microleakage scores of ceramic crowns cemented with PAN were significantly lower than those of the other subgroups (p < 0.05). © 2011 by The American College of Prosthodontists.

  1. Non-Oxide Structural Ceramics - Alloy Design for Improved Sinterability and Mechanical Performance

    National Research Council Canada - National Science Library

    Chen, I

    1998-01-01

    Research on non-oxide structure ceramics including silicon nitride, silicon carbide and titanium diboride has been conducted Multiphase silicon nitride composites with melilite and other high nitrogen...

  2. Interface-dependent resistance switching in Nd0⋅7 MnO3 ceramics

    Indian Academy of Sciences (India)

    Administrator

    EPIR) in Nd0⋅7Sr0⋅3MnO3 ceramics was studied. The results reveal that the EPIR effect originates from the interface between the electrodes and the bulk, and the EPIR ratio as well as the high and low resistance states can be strongly influ-.

  3. Influence of thermomechanical fatigue loading on the fracture resistance of all-ceramic posterior crowns.

    Science.gov (United States)

    Senyilmaz, Dilek Pinar; Canay, Senay; Heydecke, Guido; Strub, Joerg Rudolf

    2010-06-01

    This study evaluated the fracture resistance and the survival rate of different all-ceramic crowns in-vitro after thermomechanical fatigue loading in comparison to porcelain-fused-to-metal posterior crowns. Sixteen crowns for human mandibular first molars were made of each of the following: Cercon, IPS-Empress 2 In-Ceram Zirconia, Procera AllZircon and porcelain-fused-to-metal. Half of the specimens of each group was thermocycled and dynamically loaded using a chewing simulator All samples were thereafter tested for the maximum fracture resistance. The survival rates after 1-2 million cycles in the artificial mouth were 100% in all the tested crown systems. The chewing simulation and thermocycling did not significantly decrease the fracture strength of the ceramic crowns (P>0.005). The median fracture load of Cercon, Procera AllZircon, In-Ceram Zirconia and PFM was significantly higher than IPS-Empress 2 both for loaded and non loaded groups (PZirconia and PFM was not significant (P>0.005). All-ceramic systems showed fracture load values similar to those of porcelain-fused-to-metal molar crowns and therefore may be considered for use in clinical studies.

  4. Use of additives to improve microstructures and fracture resistance of silicon nitride ceramics

    Science.gov (United States)

    Becher, Paul F [Oak Ridge, TN; Lin, Hua-Tay [Oak Ridge, TN

    2011-06-28

    A high-strength, fracture-resistant silicon nitride ceramic material that includes about 5 to about 75 wt-% of elongated reinforcing grains of beta-silicon nitride, about 20 to about 95 wt-% of fine grains of beta-silicon nitride, wherein the fine grains have a major axis of less than about 1 micron; and about 1 to about 15 wt-% of an amorphous intergranular phase comprising Si, N, O, a rare earth element and a secondary densification element. The elongated reinforcing grains have an aspect ratio of 2:1 or greater and a major axis measuring about 1 micron or greater. The elongated reinforcing grains are essentially isotropically oriented within the ceramic microstructure. The silicon nitride ceramic exhibits a room temperature flexure strength of 1,000 MPa or greater and a fracture toughness of 9 MPa-m.sup.(1/2) or greater. The silicon nitride ceramic exhibits a peak strength of 800 MPa or greater at 1200 degrees C. Also included are methods of making silicon nitride ceramic materials which exhibit the described high flexure strength and fracture-resistant values.

  5. A comparison of the fracture resistance of three machinable ceramics after thermal and mechanical fatigue.

    Science.gov (United States)

    Yang, Rui; Arola, Dwayne; Han, Zhihui; Zhang, Xiuyin

    2014-10-01

    Mechanical and thermal fatigue may affect ceramic restorations in the oral environment. The purpose of this study was to determine the influence of thermal and mechanical cycling on the fracture load and fracture patterns of 3 machinable ceramics. Seventy-two human third molar teeth were prepared for bonding ceramic specimens of Sirona CEREC Blocs, IPS e.maxCAD, or inCoris ZI meso blocks. The 24 specimens of each ceramic were divided into 4 groups (n=6), which underwent no preloading (control), thermocycling (5°C-55°C, 2000 cycles), mechanical cycling (10(5) cycles, 100 N), and thermocycling (5°C-55°C, 2000 cycles) plus mechanical cycling (10(5) cycles, 100 N). The specimens were subsequently loaded to failure, and both stereomicroscopy and scanning electron microscopy were used to investigate the fracture patterns. The data were analyzed with 2-way ANOVA and the Fisher exact probability test (α=.05). Mechanical and thermal cycling had a significant influence on the critical load to failure of the 3 ceramics. No significant difference was found between mechanical cycling for 10(5) times and thermocycling for 2000 times within the same ceramic. The specimens of inCoris ZI experienced significantly higher fracture loads for all the groups. The fracture patterns of the 3 machinable ceramics showed that failure mainly occurred at the cement-dentin interface. The effects of combined thermal and mechanical cycling on the fracture load of ceramics were more significant than any individual mode of cyclic fatigue. Overall, the inCoris ZI resisted thermal and mechanical fatigue better than the Sirona CEREC and IPS e.maxCAD. Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  6. An investigation of structural design methodology for HTGR reactor internals with ceramic materials (Contract research)

    International Nuclear Information System (INIS)

    Sumita, Junya; Shibata, Taiju; Nakagawa, Shigeaki; Iyoku, Tatsuo; Sawa, Kazuhiro

    2008-03-01

    To advance the performance and safety of HTGR, heat-resistant ceramic materials are expected to be used as reactor internals of HTGR. C/C composite and superplastic zirconia are the promising materials for this purpose. In order to use these new materials as reactor internals in HTGR, it is necessary to establish a structure design method to guarantee the structural integrity under environmental and load conditions. Therefore, C/C composite expected as reactor internals of VHTR is focused and an investigation on the structural design method applicable to the C/C composite and a basic applicability of the C/C composite to representative structures of HTGR were carried out in this report. As the results, it is found that the competing risk theory for the strength evaluation of the C/C composite is applicable to design method and C/C composite is expected to be used as reactor internals of HTGR. (author)

  7. Dynamical behaviour of the resistive switching in ceramic YBCO/metal interfaces

    International Nuclear Information System (INIS)

    Acha, C

    2011-01-01

    Studies related to the dynamics of resistive switching (RS) in ceramic YBCO/metal interfaces were performed. The change in interface resistance during the application of square pulses and its current-voltage (I-V) characteristics were measured. The obtained non-linear current dependence of the differential resistance can be very well reproduced by modelling the electrical behaviour of the interface with simple circuit elements. The RS produces defined changes in the parameters of the circuit model that reveal the particular dynamics of the mechanism beneath the resistance change in complex oxide/metal interfaces.

  8. Fracture resistance of metal- and galvano-ceramic crowns cemented with different luting cements: in vitro comparative study.

    Science.gov (United States)

    Ghazy, Mohamed H; Madina, Manal M Abo

    2006-01-01

    This study aimed to compare the fracture resistance of galvano-ceramic crowns with metal-ceramic crowns cemented to natural premolar teeth with different luting cements. Sixty intact maxillary premolars were prepared to receive full-coverage crown restorations and were divided into 2 equal groups (n = 30): galvano-ceramic crowns and metal-ceramic crowns. Each group was further subdivided into 3 equal subgroups (n = 10) according to the luting cement used: zinc-phosphate, glass-ionomer, or adhesive-resin cement. The specimens were then compressively loaded until failure in a universal testing machine. The metal-ceramic crowns exhibited higher resistance to fracture compared to galvano-ceramic crowns, but both exceeded the normal documented values of occlusal masticatory forces.

  9. Lifetime Reliability Prediction of Ceramic Structures Under Transient Thermomechanical Loads

    Science.gov (United States)

    Nemeth, Noel N.; Jadaan, Osama J.; Gyekenyesi, John P.

    2005-01-01

    An analytical methodology is developed to predict the probability of survival (reliability) of ceramic components subjected to harsh thermomechanical loads that can vary with time (transient reliability analysis). This capability enables more accurate prediction of ceramic component integrity against fracture in situations such as turbine startup and shutdown, operational vibrations, atmospheric reentry, or other rapid heating or cooling situations (thermal shock). The transient reliability analysis methodology developed herein incorporates the following features: fast-fracture transient analysis (reliability analysis without slow crack growth, SCG); transient analysis with SCG (reliability analysis with time-dependent damage due to SCG); a computationally efficient algorithm to compute the reliability for components subjected to repeated transient loading (block loading); cyclic fatigue modeling using a combined SCG and Walker fatigue law; proof testing for transient loads; and Weibull and fatigue parameters that are allowed to vary with temperature or time. Component-to-component variation in strength (stochastic strength response) is accounted for with the Weibull distribution, and either the principle of independent action or the Batdorf theory is used to predict the effect of multiaxial stresses on reliability. The reliability analysis can be performed either as a function of the component surface (for surface-distributed flaws) or component volume (for volume-distributed flaws). The transient reliability analysis capability has been added to the NASA CARES/ Life (Ceramic Analysis and Reliability Evaluation of Structures/Life) code. CARES/Life was also updated to interface with commercially available finite element analysis software, such as ANSYS, when used to model the effects of transient load histories. Examples are provided to demonstrate the features of the methodology as implemented in the CARES/Life program.

  10. High temperature structural ceramic materials manufactured by the CNTD process

    International Nuclear Information System (INIS)

    Stiglich, J.J. Jr.; Bhat, D.G.; Holzl, R.A.

    1980-01-01

    Controlled Nucleation Thermochemical Deposition (CNTD) has emerged from classical chemical deposition (CVD) technology. This paper describes the techniques of thermochemical grain refinement. The effects of such refinement on mechanical properties of materials at room temperature and at elevated temperatures are outlined. Emphasis is given to high temperature structural ceramic materials such as SiC, Si 3 N 4 , AlN, and TiB 2 and ZrB 2 . An example of grain refinement accompanied by improvements in mechanical properties is SiC. Grain sizes of 500 to 1000 A have been observed in CNTD SiC with room temperature MOR of 1380 to 2070 MPa (4 pt bending) and MOR of 3450 to 4140 MPa (4 pt bending) at 1350 0 C. Various applications of these materials to the solution of high temperature structural problems are described. (author)

  11. Effect of aluminum silicate fiber modification on crack-resistance of a ceramic mould

    Directory of Open Access Journals (Sweden)

    Jiang Yehua

    2012-11-01

    Full Text Available To improve the crack-resistance of the mould for silica sol bonded quartz based ceramic mould casting, aluminum silicate fibers with the diameter ranging from 5 µm to 25 µm and the length about 1 mm were dispersed in the ceramic mould. The effect of the aluminum silicate fibers on the tensile strength, shrinkage rate and the cracking trend of the ceramic mould were investigated. In the ceramic slurry, quartz sand was applied as ceramic aggregate, silica sol containing 30% silicon dioxide as bonder, and the weight ratio of quartz sand to silica sol was 2.69; the dispersed fibers changed from 0 to 0.24vol.%. The mould samples were formed after the slurry was poured and gelled at room temperature, and then sintered at different temperatures ranging from 100 to 800 ℃ to measure the tensile strength and shrinkage rate. The results show that, with the aluminum silicate fiber addition increasing from 0 to 0.24vol.%, the tensile strength increases linearly from 0.175 MPa to 0.236 MPa, and the shrinkage rate decreases linearly from 1.75% to 1.68% for the ceramic mould sintered at 400 ℃, from 1.37% to 1.31% for the ceramic mould at room temperature. As the sintering temperature was raised from 100 ℃ to 800 ℃, the tensile strength increases, and the shrinkage rate decreases at all temperatures, compared with those without fiber dispersion, but their variation patterns remain the same. Furthermore, the cracking trend of the mould and its decreasing proportion were defined and analyzed quantitatively considering both effects of the fiber dispersion on the strength and shrinkage. The cracking trend appears to decrease linearly with increasing fiber content and to reach the maximum reduction of 28.8% when 0.24vol.% fiber was dispersed. Therefore, the investigation proposes a new method to improve the crack-resistance of the ceramic mould, i.e., inorganic fiber dispersion into the ceramic mould.

  12. Crack growth resistance of alumina, zirconia and zirconia toughened alumina ceramics for joint prostheses.

    Science.gov (United States)

    De Aza, A H; Chevalier, J; Fantozzi, G; Schehl, M; Torrecillas, R

    2002-02-01

    Mono-phase bio-ceramics (alumina and zirconia) are widely used as femoral heads in total hip replacements (THR) as an alternative to metal devices. Unfortunately, the orthopaedic community reports significant in-vivo failures. Material scientists are already familiar with composites like alumina zirconia. Since both are biocompatible, this could prove to be a new approach to implants. This paper deals with a new generation of alumina-zirconia nano-composites having a high resistance to crack propagation, and as a consequence may offer the option to improve lifetime and reliability of ceramic joint prostheses. The reliability of the above mentioned three bio-ceramics (alumina, zirconia and zirconia toughened alumina) for THR components is analysed based on the study of their slow crack-growth behaviour. The influence of the processing conditions on the microstructure development, of the zirconia toughened alumina composites and the effect of these microstructures, on its mechanical properties, are discussed.

  13. An approach to analyzing synthesis, structure and properties of bismuth titanate ceramics

    Directory of Open Access Journals (Sweden)

    Lazarević Z.

    2005-01-01

    Full Text Available The family of bismuth titanate, Bi4Ti3O12 (BIT layered-structured ferroelectrics materials is attractive from the viewpoint of their application as electronic materials such as dielectrics, piezoelectrics and pyroelectrics, because they are characterized by good stability of piezoelectric properties, a high Curie temperature and a good resistance vs temperature. Bismuth titanate (Bi4Ti3O12 powders can be prepared using different methods, depending if the creation will be film coating or ceramics. The structure and properties of bismuth titanate materials show a significance dependence on the applied synthesis method. In this review paper, we made an attempt to give an approach to analyzing the structure, synthesis methods and properties of bismuth titanate ferroelectrics materials. .

  14. Polyurethane/polysiloxane ceramer coatings: Corrosion resistant unicoat system for aircraft application

    Science.gov (United States)

    Ni, Hai

    New organic/inorganic ceramer coating system was developed using polyurethane as an organic phase and polysiloxane as the inorganic phase. The objective of the study was to develop a unicoat corrosion resistant coating which strongly adheres to aluminum substrates. The pre-ceramic silicon-oxo clusters react with the metal substrate, protecting it from oxidation, whereas the organic composition functions as a binder providing mechanical properties, optical properties, and chemical, wear and fluid resistance. The new ceramer coatings were evaluated as a replacement for chromate based coatings. The alkoxysilane-functionalized coupling agent was prepared from hexamethylene diisocyanate (HDI) isocyanurate and 3-aminopropyltriethoxysilane. The functionalized isocyanurate was characterized by 1H, 13C and 29Si NMR and electrospray ionization-mass spectrometry. An organic/inorganic hybrid coating system was formulated using the alkoxysilane-functionalized isocyanurate and HDI isocyanurate. The coating properties indicated that alkoxysilane-functionalized isocyanurate enhanced adhesion up to 500%. Based on the hybrid polyurea/alkoxysilane system, the polyurea/polysiloxane ceramer coating system was formulated with tetraethyl orthosilicate (TEOS) oligomers. Evaluation of ceramer coatings showed that coating properties were affected by both the concentration of TEOS oligomers and alkoxysilane functionalized isocyanurate. In addition, the para-toluene sulfonic acid was used to catalyze the moisture curing process for the ceramer coating system. The addition of acid catalyst further increased the adhesion. A series of high solids cycloaliphatic polyesters were synthesized to improve the UV-resistance for the organic/inorganic unicoat system. The polyurethane/polysiloxane ceramer coatings were formulated with the addition of the cycloaliphatic polyesters into the polyurea/polysiloxane system. The investigation of the polyurethane ceramer coatings indicated that the film

  15. Neutron diffraction multiphase analysis on functional heat-resistant ceramics SiC

    International Nuclear Information System (INIS)

    Li Jizhou; Yang Jilian; Kang Jian; Ye Chuntang; Cui Hongtao

    1995-01-01

    Functional heat-resistant ceramics silicon carbide SiC is a highly feasible material for high temperature engineering applications. The SiC investigated is sintered into powder sample by using industrial SiC as semifinished materials. The neutron diffraction is performed on the powder neutron diffractometer at 15 MW heavy water research reactor of the China Institute of Atomic Energy. The least-squares crystal structure and profile refinements are undertaken with the multiphase Rietveld analysis program Fullprof, which was from ILL, Grenoble, France. The results fitted for neutron data show that besides the main phase of 2H (space group of P6 3 mc), there are 4H(C6mc), 6H(C6mc) and α-SiO 2 (Fd3m) of residual impurity. The abundance of 4 phases are 2H(73.1+-2.0)%, 4H(12.8+-1.7)%, 6H(14.0+-1.1)% and α-SiO 2 <0.1%. The result shows that neutron powder diffraction is becoming more and more powerful on materials science, while the new multiphase Rietveld profile program is used. The neutron diffraction analysis can be used not only to determine the structure of materials and but also to obtain the abundance of mixture phases

  16. Inorganic glass ceramic slip rings

    Science.gov (United States)

    Glossbrenner, E. W.; Cole, S. R.

    1972-01-01

    Prototypes of slip rings have been fabricated from ceramic glass, a material which is highly resistant to deterioration due to high temperature. Slip ring assemblies were not structurally damaged by mechanical tests and performed statisfactorily for 200 hours.

  17. 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

  18. Monazite-type ceramics for conditioning of minor actinides. Structural characterization and properties

    Energy Technology Data Exchange (ETDEWEB)

    Babelot, Carole

    2013-07-01

    essential parameter is their resistance to radiation. The damage created by the recoils accompanying alpha-decay can be simulated on ceramic matrices. Preliminary experiments are realized by means of ion bombardment. Kr{sup 2+} ions are implanted in La-monazite-type pellets, and the effects on the LaPO{sub 4} structure resulting from the Raman spectroscopy are poor. On a laboratory scale, the promising characteristics of the monazite mineral are found again in the synthetic phosphate. In particular, the doping of actinide surrogates is successful and the corrosion tests under repository conditions show a good resistance of the samples. The results achieved in this work confirm that among other favorable ceramics (e.g. pyrochlore) the ''monazite-route'' has to be further pursued regarding the research on the conditioning of MA.

  19. Mapping grain boundary heterogeneity at the nanoscale in a positive temperature coefficient of resistivity ceramic

    Directory of Open Access Journals (Sweden)

    Kristina M. Holsgrove

    2017-06-01

    Full Text Available Despite being of wide commercial use in devices, the orders of magnitude increase in resistance that can be seen in some semiconducting BaTiO3-based ceramics, on heating through the Curie temperature (TC, is far from well understood. Current understanding of the behavior hinges on the role of grain boundary resistance that can be modified by polarization discontinuities which develop in the ferroelectric state. However, direct nanoscale resistance mapping to verify this model has rarely been attempted, and the potential approach to engineer polarization states at the grain boundaries, that could lead to optimized positive temperature coefficient (PTC behavior, is strongly underdeveloped. Here we present direct visualization and nanoscale mapping in a commercially optimized BaTiO3–PbTiO3–CaTiO3 PTC ceramic using Kelvin probe force microscopy, which shows that, even in the low resistance ferroelectric state, the potential drop at grain boundaries is significantly greater than in grain interiors. Aberration-corrected scanning transmission electron microscopy and electron energy loss spectroscopy reveal new evidence of Pb-rich grain boundaries symptomatic of a higher net polarization normal to the grain boundaries compared to the purer grain interiors. These results validate the critical link between optimized PTC performance and higher local polarization at grain boundaries in this specific ceramic system and suggest a novel route towards engineering devices where an interface layer of higher spontaneous polarization could lead to enhanced PTC functionality.

  20. Strengthening of oxidation resistant materials for gas turbine applications. [treatment of silicon ceramics for increased flexural strength and impact resistance

    Science.gov (United States)

    Kirchner, H. P.

    1974-01-01

    Silicon nitride and silicon carbide ceramics were treated to form compressive surface layers. On the silicon carbide, quenching and thermal exposure treatments were used, and on the silicon nitride, quenching, carburizing, and a combination of quenching and carburizing were used. In some cases substantial improvements in impact resistance and/or flexural strength were observed. The presence of compressive surface stresses was demonstrated by slotted rod tests.

  1. The effects of different polishing techniques on the staining resistance of CAD/CAM resin-ceramics.

    Science.gov (United States)

    Sagsoz, Omer; Demirci, Tevfik; Demirci, Gamze; Sagsoz, Nurdan Polat; Yildiz, Mehmet

    2016-12-01

    The purposes of this study were to evaluate the staining resistance of CAD/CAM resin-ceramics polished with different techniques and to determine the effectiveness of the polishing techniques on resin-ceramics, comparing it with that of a glazed glass-ceramic. Four different CAD/CAM ceramics (feldspathic ceramic: C-CEREC Blocs, (SIRONA) and three resin-ceramics: L-Lava Ultimate, (3M ESPE), E-Enamic, (VITA) and CS-CeraSmart, (GC)) and one light cure composite resin: ME-Clearfil Majesty Esthetic (Kuraray) were used. Only C samples were glazed (gl). Other restorations were divided into four groups according to the polishing technique: nonpolished control group (c), a group polished with light cure liquid polish (Biscover LV BISCO) (bb), a group polished with ceramic polishing kit (Diapol, EVE) (cd), and a group polished with composite polishing kit (Clearfil Twist Dia, Kuraray) (kc). Glazed C samples and the polished samples were further divided into four subgroups and immersed into different solutions: distilled water, tea, coffee, and fermented black carrot juice. Eight samples (8 × 8 × 1 mm) were prepared for each subgroup. According to CIELab system, four color measurements were made: before immersion, immersion after 1 day, after 1 week, and after 1 month. Data were analyzed with repeated measures of ANOVA (α=.05). The highest staining resistance was found in gl samples. There was no difference among gl, kc and cd ( P >.05). Staining resistance of gl was significantly higher than that of bb ( P Ceramic and composite polishing kits can be used for resin ceramics as a counterpart of glazing procedure used for full ceramic materials. Liquid polish has limited indications for resin ceramics.

  2. Plasma sprayed ceramic coatings without and with epoxy resin sealing treatment and their wear resistance

    Czech Academy of Sciences Publication Activity Database

    Ctibor, Pavel; Neufuss, Karel; Zahálka, F.; Kolman, Blahoslav Jan

    2007-01-01

    Roč. 262, 9-10 (2007), s. 1274-1280 ISSN 0043-1648 R&D Projects: GA AV ČR 1QS200430560 Institutional research plan: CEZ:AV0Z20430508 Keywords : Epoxy sealing * Alumina * Alumina-titania * Dry abrasion * Slurry abrasion Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass Impact factor: 1.395, year: 2007

  3. Energy Materials Coordinating Committee (EMACC) contractors meeting on problems and opportunities in structural ceramics

    International Nuclear Information System (INIS)

    1983-04-01

    This report consists mainly of viewographs and summaries of DOE and other programs on structural ceramics. Applications include heat engines, fusion reactors, solar absorbers, heat exchangers, coal conversion, turbines, material substitution, etc. Research centers and their capabilities are described. Panel discussions on fabrication reliability, market, ceramic producers and engine manufacturers, and conclusions are summarized

  4. Correlation of physical properties of ceramic materials with resistance to fracture by thermal shock

    Science.gov (United States)

    Lidman, W G; Bobrowsky, A R

    1949-01-01

    An analysis is made to determine which properties of materials affect their resistance to fracture by thermal stresses.From this analysis, a parameter is evaluated that is correlated with the resistance of ceramic materials to fracture by thermal shock as experimentally determined. This parameter may be used to predict qualitatively the resistance of a material to fracture by thermal shock. Resistance to fracture by thermal shock is shown to be dependent upon the following material properties: thermal conductivity, tensile strength, thermal expansion, and ductility modulus. For qualitative prediction of resistance of materials to fracture by thermal shock, the parameter may be expressed as the product of thermal conductivity and tensile strength divided by the product of linear coefficient of thermal expansion and ductility modulus of the specimen.

  5. Modelling structure and properties of amorphous silicon boron nitride ceramics

    Directory of Open Access Journals (Sweden)

    Johann Christian Schön

    2011-06-01

    Full Text Available Silicon boron nitride is the parent compound of a new class of high-temperature stable amorphous ceramics constituted of silicon, boron, nitrogen, and carbon, featuring a set of properties that is without precedent, and represents a prototypical random network based on chemical bonds of predominantly covalent character. In contrast to many other amorphous materials of technological interest, a-Si3B3N7 is not produced via glass formation, i.e. by quenching from a melt, the reason being that the binary components, BN and Si3N4, melt incongruently under standard conditions. Neither has it been possible to employ sintering of μm-size powders consisting of binary nitrides BN and Si3N4. Instead, one employs the so-called sol-gel route starting from single component precursors such as TADB ((SiCl3NH(BCl2. In order to determine the atomic structure of this material, it has proven necessary to simulate the actual synthesis route.Many of the exciting properties of these ceramics are closely connected to the details of their amorphous structure. To clarify this structure, it is necessary to employ not only experimental probes on many length scales (X-ray, neutron- and electron scattering; complex NMR experiments; IR- and Raman scattering, but also theoretical approaches. These address the actual synthesis route to a-Si3B3N7, the structural properties, the elastic and vibrational properties, aging and coarsening behaviour, thermal conductivity and the metastable phase diagram both for a-Si3B3N7 and possible silicon boron nitride phases with compositions different from Si3N4: BN = 1 : 3. Here, we present a short comprehensive overview over the insights gained using molecular dynamics and Monte Carlo simulations to explore the energy landscape of a-Si3B3N7, model the actual synthesis route and compute static and transport properties of a-Si3BN7.

  6. Characterization and evaluation of ceramic properties of clay used in structural ceramics

    International Nuclear Information System (INIS)

    Savazzini-Reis, A.; Della-Sagrillo, V.P.; Valenzuela-Diaz, F.R.

    2016-01-01

    The Brazilian red ceramic industry monthly consumes about 10.3 million tons of clay, its main raw material. In most potteries, characterization of the clay is made empirically, which can result in tiles and blocks not according to standards. This sense, this paper aims to characterize clays used in the manufacturing of red ceramic products in factory located in Colatina-ES, which appears as a ceramic pole with about twenty small and midsize industries. The clays were characterized by: Xray fluorescence, X-ray diffraction, thermal analysis (TG/DSC), granulometry and Atterberg limits. Specimens of clay and mixture containing four clays were shaped. Specimens were shaped, dried at 110°C, and burned in a kiln for 24 h. The ceramics and mechanical characteristics were evaluated: flexural strength, water absorption, apparent porosity, apparent specific mass and shrinkage by drying and firing. The characterization showed that kaolinitic clay presents high plasticity, but high porosity. The mixture formed by the four clays does not meet the requirements of the Brazilian standard clays for red ceramic. (author)

  7. Structural reliability of alumina-, feldspar-, leucite-, mica- and zirconia-based ceramics.

    Science.gov (United States)

    Tinschert, J; Zwez, D; Marx, R; Anusavice, K J

    2000-09-01

    The objective of this study was to test the hypothesis that industrially manufactured ceramic materials, such as Cerec Mark II and Zirconia-TZP, have a smaller range of fracture strength variation and therefore greater structural reliability than laboratory-processed dental ceramic materials. Thirty bar specimens per material were prepared and tested. The four-point bend test was used to determine the flexure strength of all ceramic materials. The fracture stress values were analyzed by Weibull analysis to determine the Weibull modulus values (m) and the 1 and 5% probabilities of failure. The mean strength and standard deviation values for these ceramics are as follows: (MPa+/-SD) were: Cerec Mark II, 86.3+/-4.3; Dicor, 70.3+/-12.2; In-Ceram Alumina, 429. 3+/-87.2; IPS Empress, 83.9+/-11.3; Vitadur Alpha Core, 131.0+/-9.5; Vitadur Alpha Dentin, 60.7+/-6.8; Vita VMK 68, 82.7+/-10.0; and Zirconia-TZP, 913.0+/-50.2. There was no statistically significant difference among the flexure strength of Cerec Mark II, Dicor, IPS Empress, Vitadur Alpha Dentin, and Vita VMK 68 ceramics (p>0.05). The highest Weibull moduli were associated with Cerec Mark II and Zirconia-TZP ceramics (23.6 and 18.4). Dicor glass-ceramic and In-Ceram Alumina had the lowest m values (5.5 and 5.7), whereas intermediate values were observed for IPS-Empress, Vita VMK 68, Vitadur Alpha Dentin and Vitadur Alpha Core ceramics (8.6, 8.9, 10.0 and 13.0, respectively). Except for In-Ceram Alumina, Vitadur Alpha and Zirconia-TZP core ceramics, most of the investigated ceramic materials fabricated under the condition of a dental laboratory were not stronger or more structurally reliable than Vita VMK 68 veneering porcelain. Only Cerec Mark II and Zirconia-TZP specimens, which were prepared from an industrially optimized ceramic material, exhibited m values greater than 18. Hence, we conclude that industrially prepared ceramics are more structurally reliable materials for dental applications although CAD

  8. Structures and properties of alumina-based ceramic for reconstructive oncology

    Science.gov (United States)

    Grigoriev, M. V.; Kulkov, S. N.

    2016-08-01

    The microstructure of alumina ceramics based on powders with a varying grain size has been investigated. Both commercial alumina powders and those fabricated by denitration of aluminum salts in high-frequency discharge plasma were used. It is shown that the variation of the sintering temperature and morphology of the initial powders of the particles leads to a change of the pore structure of ceramics from pore isolated clusters to a structure consisting of a ceramic skeleton and a large pore space. Changing the type of pore structure occurs at about 50% of porosity. The ceramic pore size distribution is bimodal. Dependencies final density vs initial density are linear; at the same time with increasing temperature, inclination of changes from positive to negative, indicating the change of sealing mechanisms. Extrapolation of these curves showed that they intersect with the values of density of about 2 g/cm3, which indicates the possibility of producing non-shrink ceramics. It is shown that the strength increases with increasing nanocrystalline alumina content in powder mixture. A change in the character the pore structure is accompanied by a sharp decrease in strength, which corresponds to the percolation transition in ceramics. These results showed that it is possible to obtain ceramic materials with the structure and properties similar to natural bone.

  9. Progress In Developing an Impermeable, High Temperature Ceramic Composite for Advanced Reactor Clad And Structural Applications

    International Nuclear Information System (INIS)

    Feinroth, Herbert; Hao, Bernard; Fehrenbacher, Larry; Patterson, Mark

    2002-01-01

    Most Advanced Reactors for Energy and Space Applications require higher temperature materials for fuel cladding and core internal structures. For temperatures above 500 deg. C, metal alloys do not retain sufficient strength or long term corrosion resistance for use in either water, liquid metal or gas cooled systems. In the case of water cooled systems, such metals react exo-thermically with water during core overheating accidents, thus requiring extensive and expensive emergency systems to protect against major releases. Past efforts to apply ceramic composites (oxide, carbide or nitride based) having passive safety characteristics, good strength properties at high temperatures, and reasonable resistance to crack growth, have not been successful, either because of irradiation induced effects, or lack of impermeability to fission gases. Under a Phase 1 SBIR (Small Business Innovative Research) project sponsored by DOE's Office of Nuclear Energy, the authors have developed a new material system that may solve these problems. A hybrid tubular structure (0.6 inches in outside diameter) consisting of an inner layer of monolithic silicon carbide (SiC) and outer layers of SiC-SiC composite, bonded to the inner layer, has been fabricated in small lengths. Room temperature permeability tests demonstrate zero gas leakage at pressures up to 120 psig internal pressure. Four point flexural bending tests on these hybrid tubular specimens demonstrate a 'graceful' failure mode: i.e. - the outer composite structure sustains a failure mode under stress that is similar to the yield vs. stress characteristics of metal structures. (authors)

  10. Use of thermal imaging in characterization of ceramic fiber structures

    International Nuclear Information System (INIS)

    Järveläinen, Matti; Keskinen, Lassi; Levänen, Erkki

    2013-01-01

    Fibrous bodies that contain open porosity can have a very heterogeneous structure that is difficult to characterize in terms of local flow resistance changes within the same sample. This article presents a method that is applicable for a quick analysis of flow distribution even with large samples. In this first attempt to understand how our flow distribution thermal imaging works, we present how the measuring parameters and the results correlate with sample's thickness and density. The results indicate that our method can quickly make a distinction between areas that have different flow resistances because of variations in the sample's density or wall thickness

  11. Influence of surrounding wall thickness on the fatigue resistance of molars restored with ceramic inlay

    Directory of Open Access Journals (Sweden)

    Shizuma Shibata

    2014-06-01

    Full Text Available The purpose of this study was to evaluate the influence of buccal and lingual wall thickness on the fatigue resistance of molars restored with CAD/CAM ceramic inlays. Forty human third molars were selected and divided into 4 groups, according to the remaining surrounding wall thickness chosen for inlay preparation (n = 10: G1, 2.0 mm; G2, 1.5 mm; G3, 1.0 mm; G4, 0.5 mm. All inlays were made from feldspathic ceramic blocks by a CAD/CAM system, and cemented adhesively. After 1 week stored in distilled water at 37 °C, the specimens were subjected to fatigue testing under the following protocol: 5Hz; pre-load of 200 N for 5,000 cycles, followed by increasing loads of 400, 600, 800, 1000, 1200 and 1400 N for 30,000 cycles each. The specimens were cycled until failure or completion of 185,000 cycles. The survival rate of the groups was compared using the Kaplan-Meier survival curves (p > 0.05. All specimens withstood the fatigue protocol (185,000 cycles, representing a 100% survival rate. The Kaplan-Meier survival curves showed no difference between groups. It can be concluded that the remaining tooth wall thickness did not influence the fatigue resistance of molars restored with CAD/CAM ceramic inlays.

  12. Influence of surrounding wall thickness on the fatigue resistance of molars restored with ceramic inlay.

    Science.gov (United States)

    Shibata, Shizuma; Gondo, Renata; Araújo, Élito; Mello Roesler, Carlos Rodrigo de; Baratieri, Luiz Narciso

    2014-01-01

    The purpose of this study was to evaluate the influence of buccal and lingual wall thickness on the fatigue resistance of molars restored with CAD/CAM ceramic inlays. Forty human third molars were selected and divided into 4 groups, according to the remaining surrounding wall thickness chosen for inlay preparation (n=10): G1, 2.0 mm; G2, 1.5 mm; G3, 1.0 mm; G4, 0.5 mm. All inlays were made from feldspathic ceramic blocks by a CAD/CAM system, and cemented adhesively. After 1 week stored in distilled water at 37 °C, the specimens were subjected to fatigue testing under the following protocol: 5Hz; pre-load of 200 N for 5,000 cycles, followed by increasing loads of 400, 600, 800, 1000, 1200 and 1400 N for 30,000 cycles each. The specimens were cycled until failure or completion of 185,000 cycles. The survival rate of the groups was compared using the Kaplan-Meier survival curves (p>0.05). All specimens withstood the fatigue protocol (185,000 cycles), representing a 100% survival rate. The Kaplan-Meier survival curves showed no difference between groups. It can be concluded that the remaining tooth wall thickness did not influence the fatigue resistance of molars restored with CAD/CAM ceramic inlays.

  13. Development of wear resistant ceramic coatings for diesel engine components

    Energy Technology Data Exchange (ETDEWEB)

    Haselkorn, M.H. (Caterpillar, Inc., Peoria, IL (United States))

    1992-04-01

    Improved fuel economy and a reduction of emissions can be achieved by insulation of the combustion chamber components to reduce heat rejection. However, insulating the combustion chamber components will also increase the operating temperature of the piston ring/cylinder liner interface from approximately 150{degree}C to over 300{degree}C. Existing ring/liner materials can not withstand these higher operating temperatures and for this reason, new materials need to be developed for this critical tribological interface. The overall goal of this program is the development of piston ring/cylinder liner material pairs which would be able to provide the required friction and wear properties at these more severe operating conditions. More specifically, this program first selected, and then evaluated, potential d/wear resistant coatings which could be applied to either piston rings an or cylinder liners and provide, at 350{degree}C under lubricated conditions, coefficients of friction below 0.1 and wear rates of less than 25 {times} lO{sup {minus}6} mm/hour. The processes selected for applying the candidate wear resistant coatings to piston rings and/or cylinder liners were plasma spraying, chemical vapor, physical vapor and low temperature arc vapor deposition techniques as well as enameling techniques.

  14. Optimization of the Structure of a Ceramic-Aluminum Alloy Composite Subjected to the Impact of Hard Steel Projectiles

    Science.gov (United States)

    Morka, A.; Kędzierski, P.; Muzolf, P.

    2016-07-01

    The optimization process for a composite panel with an Al2O3-AA2024 percolation phase subjected to a perpendicular impact of a 7.62 × 54R B32 Armor Piercing projectile is described. It is found that metal-matrix composite/ceramic-matrix composite structures have a lower ballistic resistance than structures in which a hard layer supported by a plastic one. Optimization revealed that the best composite panel with an Al2O3-AA2024 percolation phase could be obtained when the probability distribution of individual materials was described by a highly nonlinear function.

  15. Insulation Resistance and Leakage Currents in Low-Voltage Ceramic Capacitors with Cracks

    Science.gov (United States)

    Teverovsky, Alexander A.

    2016-01-01

    Measurement of insulation resistance (IR) in multilayer ceramic capacitors (MLCCs) is considered a screening technique that ensures the dielectric is defect-free. This work analyzes the effectiveness of this technique for revealing cracks in ceramic capacitors. It is shown that absorption currents prevail over the intrinsic leakage currents during standard IR measurements at room temperature. Absorption currents, and consequently IR, have a weak temperature dependence, increase linearly with voltage (before saturation), and are not sensitive to the presence of mechanical defects. In contrary, intrinsic leakage currents increase super-linearly with voltage and exponentially with temperature (activation energy is in the range from 0.6 eV to 1.1 eV). Leakage currents associated with the presence of cracks have a weaker dependence on temperature and voltage compared to the intrinsic leakage currents. For this reason, intrinsic leakage currents prevail at high temperatures and voltages, thus masking the presence of defects.

  16. The dynamic properties of sandwich structures based on metal-ceramic foams.

    Science.gov (United States)

    2014-01-01

    The present research program has studied the fracture properties of closed pore metal-ceramic foams for their potential applications as core systems in sandwich structures. The composite foams were created at Fireline, Inc. (Youngstown, OH) using the...

  17. Ceramic Composite Mechanical Fastener System for High-Temperature Structural Assemblies, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Hot structures fabricated from ceramic composite materials are an attractive design option for components of future high-speed aircraft, re-entry vehicles and...

  18. Fracture resistance of endodontically treated teeth restored with ceramic inlays and different base materials.

    Science.gov (United States)

    Saridag, Serkan; Sari, Tugrul; Ozyesil, Atilla Gokhan; Ari Aydinbelge, Hale

    2015-01-01

    This study evaluated the fracture resistance of endodontically treated teeth restored with different base materials and mesioocclusal-distal (MOD) ceramic inlays. Fifty mandibular molars were assigned into five groups (n=10 per group). Group1 (control) comprised intact molar teeth without any treatment. Teeth in other groups were subjected to root canal treatment and restored with MOD ceramic inlays on different base materials. In Group 2, base material was zinc phosphate cement; Group 3's was glass ionomer cement; Group 4's was composite resin, and Group 5's was composite resin reinforced with fiber. Finally, a continuous occlusal load was applied until fracture occurred. Mean fracture resistance of Group 1 (3,027 N) was significantly higher than the other groups (890, 1,070, 1,670, 1,226 N respectively). Fracture resistance of Group 4 was statistically comparable with Group 5 and significantly higher than Groups 2 and 3 (pinlay restorations could affect the fracture resistance of endodontically treated teeth.

  19. Gloss and Stain Resistance of Ceramic-Polymer CAD/CAM Restorative Blocks.

    Science.gov (United States)

    Lawson, Nathaniel C; Burgess, John O

    2016-03-01

    To evaluate the gloss and stain resistance of several new ceramic-polymer CAD/CAM blocks Specimens (4 mm) were sectioned from: Enamic (polymer-infused ceramic), LAVA Ultimate (nano-ceramic reinforced polymer), e.max (lithium disilicate), Paradigm C (porcelain), and Paradigm MZ100 (composite). Specimens were wet polished on a polishing wheel to either 320 grit silicon paper (un-polished, N = 8) or 2000 grit silicon carbide papers followed by a 0.05 μm alumina slurry (polished, N = 8). Initial gloss and color (L*a*b*) values were measured. Specimens were stored in a staining solution at 37°C in darkness for 12 days (simulating 1 year). After storage, L*a*b* values re-measured. Change in color was reported as ΔE00 based on the CIEDE2000 formula. Gloss and ΔE00 were analyzed by two-way analysis of variance (ANOVA) (alpha = .05). Separate one-way ANOVA and Tukey post-hoc analyses were performed for both polish conditions and all materials. Two-way ANOVA showed that factors material, polish and their interaction were significant for both gloss and ΔE00 (p < .01). Post-hoc analysis reveals that polished specimens had significantly less color change than un-polished specimens for Paradigm C and LAVA Ultimate. E.max had significantly higher gloss and less color change than all other materials. The composition and polish of CAD/CAM materials affects gloss and stain resistance. Ceramic-polymer hybrid materials can achieve the high gloss required for esthetic restorations. These materials should be polished in order to minimize staining. If polished, all of the tested materials exhibited clinically acceptable color changes at 1 year of simulated staining. (J Esthet Restor Dent 28:S40-S45, 2016). © 2015 Wiley Periodicals, Inc.

  20. Chemical Routes to Ceramics With Tunable Properties and Structures

    National Research Council Canada - National Science Library

    Sneddon, Larry G

    2006-01-01

    .... Research was focused on the development of new precursor routes to a number of ultra high temperature ceramics, including hafnium and zirconium -boride, -carbide and -nitride materials, and on the...

  1. Post-fatigue fracture resistance of metal core crowns: press-on metal ceramic versus a conventional veneering system.

    Science.gov (United States)

    Solá-Ruiz, M Fernanda; Agustín-Panadero, Rubén; Campos-Estellés, Carlos; Labaig-Rueda, Carlos

    2015-04-01

    The aim of this in vitro study was to compare the mechanical failure behavior and to analyze fracture characteristics of metal ceramic crowns with two veneering systems - press-on metal (PoM) ceramic versus a conventional veneering system - subjected to static compressive loading. Forty-six crowns were constructed and divided into two groups according to porcelain veneer manufacture. Group A: 23 metal copings with porcelain IPS-InLine veneering (conventional metal ceramic). Group B: 23 metal copings with IPS-InLine PoM veneering porcelain. After 120,000 fatigue cycles, the crowns were axially loaded to the moment of fracture with a universal testing machine. The fractured specimens were examined under optical stereomicroscopy and scanning electron microscope. Fracture resistance values showed statistically significant differences (Student's t-test) regarding the type of ceramic veneering technique (p=0.001): Group A (conventional metal ceramics) obtained a mean fracture resistance of 1933.17 N, and Group B 1325.74N (Press-on metal ceramics). The most common type of fracture was adhesive failure (with metal exposure) (p=0.000). Veneer porcelain fractured on the occlusal surface following a radial pattern. Metal ceramic crowns made of IPS InLine or IPS InLine PoM ceramics with different laboratory techniques all achieved above-average values for clinical survival in the oral environment according to ISO 6872. Crowns made with IPS InLine by conventional technique resisted fracture an average of 45% more than IPS InLine PoM fabricated with the press-on technique. Key words:Mechanical failure, conventional feldspathic, pressable ceramic, chewing simulator, thermocycling, compressive testing, fracture types, scanning electron microscope.

  2. Comparison of fracture resistance of teeth restored with ceramic inlay and resin composite: An in vitro study

    Directory of Open Access Journals (Sweden)

    Priti D Desai

    2011-01-01

    Conclusion: The fracture resistant strength of teeth restored with ceramic inlay was comparable to that of the normal intact teeth or slightly higher, while teeth restored with direct composite resin restoration showed less fracture resistant strength than that of the normal teeth.

  3. A novel approach for the fabrication of carbon nanofibre/ceramic porous structures

    KAUST Repository

    Walter, Claudia

    2013-11-01

    This paper describes the fabrication of hybrid ceramic/carbon scaffolds in which carbon nanofibres and multi-walled carbon nanotubes fully cover the internal walls of a microporous ceramic structure that provides mechanical stability. Freeze casting is used to fabricate a porous, lamellar ceramic (Al2O3) structure with aligned pores whose width can be controlled between 10 and 90μm. Subsequently, a two step chemical vapour deposition process that uses iron as a catalyst is used to grow the carbon nanostructures inside the scaffold. This catalyst remains in the scaffold after the growth process. The formation of the alumina scaffold and the influence of its structure on the growth of nanofibres and tubes are investigated. A set of growth conditions is determined to produce a dense covering of the internal walls of the porous ceramic with the carbon nanostructures. The limiting pore size for this process is located around 25μm. © 2013 Elsevier Ltd.

  4. A ceramic nozzle for the NASA-Langley 2.4-m /8.0-ft/ high temperature structures tunnel

    Science.gov (United States)

    Buckley, J. D.; Vasquez, P.

    1982-01-01

    Two materials, a refractory castable ceramic and a SiO2-SiO2 composite, were fabricated as nozzle inserts for the Langley Research Center's 2.4-m (8.0-ft) high temperature structures tunnel. The high pressure and intense heat of the CH4-air products of the combustion-gas stream limits the materials that can be used in this tunnel. The castable-ceramic material showed good resistance to erosion and the thermal loads imposed on it by the gas stream but failed in tension when subjected to high hoop stresses. The SiO2-SiO2-composite nozzle insert withstood the thermomechanical loads but eroded unacceptably with increasing test temperature and pressure.

  5. Evaluation of the physicochemical properties of structured materials: metallic, polymeric and ceramic, for the treatment of sour gases

    International Nuclear Information System (INIS)

    Salazar, A.; Chavez, R. H.; Olea, O.; Solis, D.

    2013-01-01

    in this work the physicochemical properties of three structured materials: metallic, polymeric and ceramic, from Sulzer Brothers Limited brand, are studied in order to removal sour gases, by absorption process, in aqueous solution of Monoethanolamine (Mea), at 30% weight. Mechanical properties, chemical composition, morphology and corrosion resistance were determined, using different characterization techniques, such as: 1) mechanically, according to standard procedures Astm E-384-1990, 2) chemically, by the corrosion resistance in the presence of an electrochemical cell, in aqueous solution of H 2 SO 4 , 1 N by Astm G-5-1999, 3) morphologically by scanning electron microscopy technique, and 4) efficiency of separation, by the gas chromatography technique in order to determine the chemical absorption of CO 2 by Mea. The ceramic material was the hardest with 700 Hk value and tensile strength of 90 MPa, likewise showed resistance to corrosion of 10.28 m py, separation efficiency of 74% CO 2 , at 10 minutes. The metallic material had a hardness of 190 Hk and it was the most resistant of tension, with 831 MPa, and corrosion resistance of 780.4 x 10 -6 m py, likewise promoted CO 2 separation efficiency of 90% during the evaluation. The polymeric material presented hardness of 20 Hk and 35 MPa and it was not suffered surface change with electrochemical attack, with 282.4 x 10 -6 m py, and separation efficiency of 88%. Therefore the polymer was the most ductile, with smooth surface and greater resistance with H 2 SO 4 . The metal material was more resistant to plastic deformation and more corrugated surface and the second resistance in the presence of acid medium in aqueous solutions. For all the above, the metallic material is recommended by its greater separation in the reduction of acid gases and the polymer due to its greater chemical resistance. (Author)

  6. 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.

  7. Fatigue resistance of 2 different CAD/CAM glass-ceramic materials used for single-tooth implant crowns.

    Science.gov (United States)

    Çavuşoğlu, Yeliz; Sahin, Erdal; Gürbüz, Riza; Akça, Kivanç

    2011-10-01

    To evaluate the fatigue resistance of 2 different CAD/CAM in-office monoceramic materials with single-tooth implant-supported crowns in functional area. A metal experimental model with a dental implant was designed to receive in-office CAD/CAM-generated monoceramic crowns. Laterally positioned axial dynamic loading of 300 N at 2 Hz was applied to implant-supported crowns machined from 2 different glass materials for 100,000 cycle. Failures in terms of fracture, crack formation, and chipping were macroscopically recorded and microscopically evaluated. Four of 10 aluminasilicate glass-ceramic crowns fractured at early loading cycles, the rest completed loading with a visible crack formation. Crack formation was recorded for 2 of 10 leucite glass-ceramic crowns. Others completed test without visible damage but fractured upon removal. Lack in chemical adhesion between titanium abutment and dental cement likely reduces the fatigue resistance of machinable glass-ceramic materials. However, relatively better fractural strength of leucite glass-ceramics could be taken into consideration. Accordingly, progress on developmental changes in filler composition of glass-ceramics may be promising. Machinable glass-ceramics do not possess sufficient fatigue resistance for single-tooth implant crowns in functional area.

  8. Sulphuric Acid Resistant of Self Compacted Geopolymer Concrete Containing Slag and Ceramic Waste

    Directory of Open Access Journals (Sweden)

    Shafiq I.

    2017-01-01

    Full Text Available Malaysia is a one of the developing countries where the constructions of infrastructure is still ongoing, resulting in a high demand for concrete. In order to gain sustainability factors in the innovations for producing concrete, geopolymer concrete containing granulated blast-furnace slag and ceramics was selected as a cement replacement in concrete for this study. Since Malaysia had many ceramic productions and uses, the increment of the ceramic waste will also be high. Thus, a new idea to reuse this waste in construction materials have been tested by doing research on this waste. Furthermore, a previous research stated that Ordinary Portland Cement concrete has a lower durability compared to the geopolymer concrete. Geopolymer binders have been reported as being acid resistant and thus are a promising and alternative binder for sewer pipe manufacture. Lack of study regarding the durability of the geopolymer self-compacting concrete was also one of the problems. The waste will be undergoing a few processes in the laboratory in order to get it in the best form before undergoing the next process as a binder in geopolymer concrete. This research is very significant in order to apply the concept of sustainability in the construction field. In addition, the impact of this geopolymer binder is that it emits up to nine times less CO2 than Portland Cement.

  9. Scientific activity within the targeted research project: Metallic, ceramic and organic nanomaterials: processing - structure - properties - applications

    International Nuclear Information System (INIS)

    Leonowicz, M.; Kurzydlowski, K.

    2003-01-01

    In november 2000 Polish State Committee for Scientific Research (KBN) launched a Targeted Research Project 'Metallic, ceramic and organic nanomaterials: processing - structure - properties - applications'. The structural materials, covered by the project, comprise analysis of the suitability of heavy deformation routes for nanocrystallization of metals and alloys, Al-based glass-ceramics, ceramic matrix nanocomposites, gradient materials. Also surface engineering methods and polymer matrix nanocomposites are studied. Novel methods for the processing and compacting of nanomaterials are also researched. Among functional materials: materials for batteries soft and hard magnetic materials and nanomaterials, giant magnetoresistance and light emitting materials are studied. Basic phenomena such as mechanics of superplastic deformation of ceramics, demagnetization processes in ferromagnetic nanomaterials, transport processes in ionic conductivity materials are also investigated. Overview of the main research direction and selected achievements of the project are presented. (author)

  10. In situ hydroxyapatite nanofiber growth on calcium borate silicate ceramics in SBF and its structural characteristics.

    Science.gov (United States)

    Pu, Yinfu; Huang, Yanlin; Qi, Shuyun; Chen, Cuili; Seo, Hyo Jin

    2015-10-01

    A novel calcium silicate borate Ca11Si4B2O22 ceramic was firstly prepared by the conventional solid-state reaction. In vitro hydroxyapatite mineralization was investigated by soaking the ceramics in simulated body fluid (SBF) solutions at body temperature (37 °C) for various time periods. Scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD) measurements were applied to investigate the samples before and after the immersion of ceramics in SBF solution. The elemental compositions of a hydroxyapatite layer on the ceramics during the mineralization were confirmed by X-ray energy-dispersive spectra (EDS). Meanwhile, the bending strength and elastic modulus of Ca11Si4B2O22 ceramics were also measured, which indicate that the biomaterials based on Ca11Si4B2O22 ceramics possess bioactivity and might be a potential candidate as biomaterials for hard tissue repair. The bioactive mineralization ability was evaluated on the base of its crystal structural characteristics, i.e., silanol (Si-OH) and B-OH groups can be easily induced on the surface of Ca11Si4B2O22 ceramics soaked in SBF solutions. Copyright © 2015 Elsevier B.V. All rights reserved.

  11. STRUCTURE AND PROPERTIES OF A CERAMIC BRICK MODIFIED WITH TECHNOGENIC MINERAL SYSTEMS

    Directory of Open Access Journals (Sweden)

    DEREVIANKO V. N.

    2016-07-01

    Full Text Available Summary. Problem statement. One way to conserve the scarce high-quality raw materials resources and to reduce transport and energy costs is to use the accumulated technogenic mineral systems, as well as to study technogenic raw materials which were not previously used [1-3]. A shortage of high plasticity clays determines the need for using local low-grade loamy raw materials for the manufacture of wall ceramics. Strength properties of the ceramic brick can be improved by using expensive corrective additives or local technogenic raw materials [4-7]. Purpose. Development of compositions for the ceramic brick, modified with technogenic mineral systems. Conclusion. The author has studied the influence of the mixture ratio on the structure and fundamental physical and mechanical properties of the ceramic brick modified with technogenic mineral systems. The author has also developed the best ceramic batch compositions based on technogenic mineral systems conferring the required physical and mechanical parameters of the ceramic brick; they consist of: overburden (67%, refuse heap (28% and red mud from NGZ (Mykolaiv Alumina Refinery (5% for making 150 Grade ceramic brick with an average density of 1,650-1,730 kg/m3 at a temperature of 850°C, which allows to reduce firing energy costs. It has been established that the sintering initiation temperature of the modified mixture decreases by 150-200°C compared to the unmodified one.

  12. The structure and piezoelectric properties of (Ca1-xSrx)Bi4Ti4O15 ceramics

    International Nuclear Information System (INIS)

    Zheng Liaoying; Li Guorong; Zhang Wangzhong; Chen, Daren; Yin Qinrui

    2003-01-01

    In this paper, the structure and piezoelectric properties of (Ca 1-x Sr x )Bi 4 Ti 4 O 15 ceramics (x=0-1.0) are investigated. The formation of single orthorhombic phase is verified by XRD. The dependence of dielectric and piezoelectric properties on x is also determined. The results show that the excellent properties could be found in the composition of x=0.4. In that composition, d 33 =14.9, T C =677 deg. C and the DC resistivity is decuplely higher than that of BST (SrBi 4 Ti 4 O 15 ) and CBT (CaBi 4 Ti 4 O 15 )

  13. Properties and performance of polysiloxane-derived ceramic matrix in heat resistant composites reinforced with R-glass or fine ceramic fibres

    Czech Academy of Sciences Publication Activity Database

    Černý, Martin; Glogar, Petr; Sucharda, Zbyněk; Machovič, V.

    2005-01-01

    Roč. 49, č. 3 (2005), s. 145-152 ISSN 0862-5468 R&D Projects: GA ČR(CZ) GA106/02/0177; GA ČR(CZ) GP106/02/P025 Institutional research plan: CEZ:AV0Z30460519 Keywords : polysiloxane resin * fibre-reinforced composite * mechanical properties Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass Impact factor: 0.463, year: 2005

  14. Surface electric resistance of YBa2Cu3O7-δ ceramics and its dependence on magnetic field

    International Nuclear Information System (INIS)

    Gorochev, O.A.; Graboj, I.Eh.; Kaul', A.R.; Mitrofanov, V.P.

    1989-01-01

    Method of dielectric resonator in the 4.2-300 K temperature range is used to measure surface electric resistance of YBa 2 Cu 3 O 7-δ ceramics samples produced by different technologies. The temperature dependence of surface resistance near transition temperature is calculated. At 77.3 K dependence of electric resistance on external magnetic field at H≤200Oe is determined. Calculated dependence is verified in experiment

  15. 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.

  16. Influence of Sintering Temperature on Pore Structure and Electrical properties of Technologically Modified MgO-Al2O3 Ceramics

    Directory of Open Access Journals (Sweden)

    Halyna Klym

    2015-03-01

    Full Text Available Technologically modified spinel ceramics are prepared from Al2O3 and 4MgCO3×Mg(OH2×5H2O powders at 1200, 1300 and 1400 oC. The influence of sintering temperature on porous structure and exploitation properties of obtained humidity-sensitive MgO-Al2O3 ceramics are studied. It is shown that increasing of preparing temperature from 1200 to 1400 oC result in transformation of pore size distribution in ceramics from tri- to bi-modal including the open macro- and mesopores with sizes from tem to hundreds nm and nanopores until to a few nm. The studied ceramic elements with electrical resistances ~ 10-2-102 MОhm are high humidity sensitive in the region of 30-95 % with minimal hysteresis in adsorption-desorption cycles. It is established that increasing of humidity sensitivity in ceramics are related to achievement near to optimum pore size distribution and quantity of pores in the all regions. Prolonged degradation transformation in ceramics at higher temperature and relative humidity result in lose sensitivity up to 40-50 %.DOI: http://dx.doi.org/10.5755/j01.ms.21.1.5189

  17. Use of residues proceeding from marbles and granites finishing and manufacturing processes as raw material for structural ceramic

    International Nuclear Information System (INIS)

    Mello, Roberta Monteiro de

    2006-01-01

    In order to decrease environmental impact, caused by mud discarding and clay extraction in the ceramic industry, it was used residual mud from marble and granite companies for structural ceramic. Samples were collected in twelve different marble companies located at the metropolitan region of Sao Paulo. However, only four samples were selected, based on its different characteristics. Clay stone was the raw material chosen to prepare the structural ceramic, considering its high use in this segment. Samples and clay stone were both analysed by the following procedures: granulometric analysis, x-rays fluorescent chemical analysis and x-rays diffraction mineralogical analysis, besides, tests in the samples were conducted following NBR 10004 standards. Once raw materials were characterized, the plasticity test was conducted. Test specimen were molded with different levels of mud, then burned and submitted to technological tests, such as: mechanical resistance, water absorption, porosity, specific gravity and retraction, material dilation before burning process and scanning electron microscopy. The final results have shown the viability of using this kind of mud, and pointed some advantages on its usage, but taking in consideration some previous conditions to be adopted. (author)

  18. Heat-Resistant Ceramic Pigments on the Base of Waste Vanadium Catalyst and Alumina

    Directory of Open Access Journals (Sweden)

    M. B. Sedelnikova

    2013-01-01

    Full Text Available Ceramic pigments on the base of technogenic silica-containing material—waste vanadium catalyst were obtained in this work. Corundum is identified along with the predominant mullite phase in the composition of pigments. The ions of nickel, chromium, and iron are embedded in the structure if the concentration of the corresponding oxide in the initial mixture does not exceed 10 wt.%. In this case, the oxide is not identified in a free form according to the results of X-ray diffraction analysis. Spinel CoAl2O4 is formed in cobalt pigments. The developed pigments keep the firing temperature up to 1200°C. The obtained pigments may be recommended for ceramic paints and colored glazes for building materials.

  19. Data on post irradiation experiments of heat resistant ceramic composite materials. PIE for 97M-13A

    Energy Technology Data Exchange (ETDEWEB)

    Baba, Shin-ichi; Ishihara, Masahiro; Souzawa, Shizuo [Japan Atomic Energy Research Inst., Oarai, Ibaraki (Japan). Oarai Research Establishment; Sekino, Hajime [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    2003-03-01

    The research on the radiation damage mechanism of heat resistant ceramic composite materials is one of the research subjects of the innovative basic research in the field of high temperature engineering, using the High Temperature engineering Test Reactor (HTTR). Three series of irradiation tests on the heat resistant ceramic composite materials, first to third irradiation test program, were carried out using the Japan Material Testing Reactor (JMTR). This is a summary report on the first irradiation test program; irradiation induced dimensional change, thermal expansion coefficient, X-ray diffraction and {gamma}-ray spectrum are reported. (author)

  20. Fracture resistance of a selection of full-contour all-ceramic crowns: an in vitro study.

    Science.gov (United States)

    Zesewitz, Tim F; Knauber, Andreas W; Nothdurft, Frank P

    2014-01-01

    This study aimed to evaluate the fracture resistance of monolithic single crowns made from zirconia (ZI), lithium disilicate (LS2), or feldspar ceramic (FC). Five groups of crowns representing a maxillary first molar were made with the appropriate dimensions according to the manufacturer's instructions. The ZI and LS2 crowns were luted adhesively or cemented conventionally on a metal abutment tooth analog. The feldspar ceramic crowns were luted adhesively. All specimens underwent axial loading until fracture. The crowns in the ZI groups possessed the highest fracture resistance independent of the mode of fixation.

  1. In vitro comparative analysis of resistance to compression of laboratory resin composites and a ceramic system.

    Science.gov (United States)

    Montenegro, Alexandre Campos; do Couto, Cintia Fernandes; Ventura, Paulo Roberto Rezende; Gouvea, Cresus Vinicius Depes; Machado, Aldir Nascimento

    2010-01-01

    Restorative materials must be capable not only of restoring the patient's masticatory function, but also to rescue the self-esteem of those maculated by a disharmonious smile. Among the esthetic materials available on the market, the choice frequently lies between ceramic or indirect laboratory resin restorations. This study assessed the resistance to compression of two laboratory resins found on the market, namely Artglass and Targis, considering Omega 900 ceramic from Vita as control. With the aid of stainless steel matrices, with internal dimensions of 8.0 mm diameter at the base, 9.0 mm in the top portion and 4.0 mm height, 15 test specimens were made, being 5 of each material to be tested. The test specimens were kept in distilled water for 72 hours and submitted to an axial load by the action of a point with a rounded tip 2 mm in diameter, adapted to an EMIC 500 universal test machine. The compression speed was 0.5 mm/min, with a load cell capacity of 200 Kgf. The means of the results were calculated in kilogram-force (Kgf). The results found were treated by analysis of variance (ANOVA) and the differences found among the groups were identified by the Tukey test (5%). It was observed that the material Omega 900 (R) offered significantly greater resistance to compression than the other two materials, which did not present statistically significant difference between them.

  2. Needs assessment for nondestructive testing and materials characterization for improved reliability in structural ceramics for heat engines

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, D.R.; McClung, R.W.; Janney, M.A.; Hanusiak, W.M.

    1987-08-01

    A needs assessment was performed for nondestructive testing and materials characterization to achieve improved reliability in ceramic materials for heat engine applications. Raw materials, green state bodies, and sintered ceramics were considered. The overall approach taken to improve reliability of structural ceramics requires key inspections throughout the fabrication flowsheet, including raw materials, greed state, and dense parts. The applications of nondestructive inspection and characterization techniques to ceramic powders and other raw materials, green ceramics, and sintered ceramics are discussed. The current state of inspection technology is reviewed for all identified attributes and stages of a generalized flowsheet for advanced structural ceramics, and research and development requirements are identified and listed in priority order. 164 refs., 3 figs.

  3. Surface modification technique of structural ceramics: ion implantation-assisted multi-arc ion plating

    International Nuclear Information System (INIS)

    Peng Zhijian; Miao Hezhuo; Si Wenjie; Qi Longhao; Li Wenzhi

    2003-01-01

    Through reviewing the advantages and disadvantages of the existed surface modification techniques, a new technique, ion implantation-assisted multi-arc ion plating, was proposed. Using the proposed technique, the surfaces of silicon nitride ceramics were modified by Ti ion implantation, and then three kinds of ternary coatings, (Ti,Al)N, (Ti,Zr)N and (Ti,Cr)N, were deposited on the as-implanted ceramics. The coatings prepared by this technique are of high-hardness and well adhesive to the ceramic substrates. The maximal hardness measured by nanoindentation tests is more than 40 GPa. The maximal critical load by nanoscratch tests is more than 60 mN. The cutting tools prepared by this technique with the presented coatings are of excellent performance in industrial applications. The technique may be promising for the surface modification of structural ceramics. (orig.)

  4. Fracture resistance of CAD-CAM monolithic ceramic and veneered zirconia molar crowns after aging in a mastication simulator.

    Science.gov (United States)

    Bankoğlu Güngör, Merve; Karakoca Nemli, Secil

    2018-03-01

    The demand for ceramic restorations has increased over the past years, and now various machinable materials can be used for chairside computer-aided design and computer aided manufacturing (CAD-CAM) systems. Limited studies of these new materials make it difficult to evaluate their mechanical performance, advantages, and limitations. The purpose of this in vitro study was to investigate the fracture resistance of CAD-CAM monolithic ceramic and veneered zirconia molar crowns after thermomechanical aging. A mandibular first molar tooth was prepared, and 12 different experimental groups were generated (n=10). An aging procedure was performed by subjecting the specimens to 12×10 5 mechanical cycles and 5000 thermocycles. Survival analysis was performed according to the thermomechanical aging. The fracture resistance (load at fracture) of all specimens was evaluated with 1-way analysis of variance after the means had been compared using the Tukey honest significant difference test and Weibull distributions of the experimental groups (α=.05). According to the results, the differences between the fracture resistance of the groups were found to be significant. Restorations in the dual network ceramic crown group fractured catastrophically during thermomechanical aging. In all groups, the highest value was found for monolithic zirconia, followed by monolithic lithium disilicate crowns (Pcrowns made of lithium disilicate derivates and zirconia crowns veneered with lithium disilicate ceramic showed no differences from each other (P>.05). The Weibull modulus (m) ranged from 4.22 to 8.58, and conventionally veneered and overpressed zirconia showed the lowest Weibull modulus values among the tested groups, indicating greater variation of the data. The highest fracture resistance was observed for yttria-stabilized zirconia crowns, followed by lithium disilicate derivates. Veneered zirconia restorations generally showed lower resistance than these ceramics. The dual network

  5. In situ hydroxyapatite nanofiber growth on calcium borate silicate ceramics in SBF and its structural characteristics

    Energy Technology Data Exchange (ETDEWEB)

    Pu, Yinfu; Huang, Yanlin; Qi, Shuyun [College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123 (China); Chen, Cuili [Department of Physics and Interdisciplinary Program of Biomedical, Mechanical & Electrical Engineering, Pukyong National University, Busan 608-737 (Korea, Republic of); Seo, Hyo Jin, E-mail: hjseo@pknu.ac.kr [Department of Physics and Interdisciplinary Program of Biomedical, Mechanical & Electrical Engineering, Pukyong National University, Busan 608-737 (Korea, Republic of)

    2015-10-01

    A novel calcium silicate borate Ca{sub 11}Si{sub 4}B{sub 2}O{sub 22} ceramic was firstly prepared by the conventional solid-state reaction. In vitro hydroxyapatite mineralization was investigated by soaking the ceramics in simulated body fluid (SBF) solutions at body temperature (37 °C) for various time periods. Scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD) measurements were applied to investigate the samples before and after the immersion of ceramics in SBF solution. The elemental compositions of a hydroxyapatite layer on the ceramics during the mineralization were confirmed by X-ray energy-dispersive spectra (EDS). Meanwhile, the bending strength and elastic modulus of Ca{sub 11}Si{sub 4}B{sub 2}O{sub 22} ceramics were also measured, which indicate that the biomaterials based on Ca{sub 11}Si{sub 4}B{sub 2}O{sub 22} ceramics possess bioactivity and might be a potential candidate as biomaterials for hard tissue repair. The bioactive mineralization ability was evaluated on the base of its crystal structural characteristics, i.e., silanol (Si–OH) and B–OH groups can be easily induced on the surface of Ca{sub 11}Si{sub 4}B{sub 2}O{sub 22} ceramics soaked in SBF solutions. - Highlights: • Calcium silicate borate Ca{sub 11}Si{sub 4}B{sub 2}O{sub 22} ceramics were developed as a new biomaterial. • Ca{sub 11}Si{sub 4}B{sub 2}O{sub 22} shows a superior in vitro bioactivity by inducing bone-like apatite. • Ca{sub 11}Si{sub 4}B{sub 2}O{sub 22} has good mechanical properties as potential candidate biomaterials. • The structure with SiO{sub 4} and BO{sub 3} groups is favorable for hydroxyapatite formation.

  6. Scandium doped Strontium Titanate Ceramics: Structure, Microstructure, and Dielectric Properties

    Directory of Open Access Journals (Sweden)

    Tkach, Alexander

    2008-08-01

    Full Text Available Sc-doped strontium titanate (ST ceramics were synthesised by solid state reaction, according to the composition Sr1-1.5xScxTiO3 with x = 0-0.01. Structural properties and microstructure development was examined by XRD and SEM. The dielectric properties were evaluated as a function of the temperature and frequency in the radio frequency range. Lattice parameter, density and grain size, were found to decrease slightly with increasing Sc content. The dielectric permittivity and losses decrease also. Sc-doping has only a weak effect on the quantum paraelectric behaviour of ST and no dielectric anomaly was observed, what is probably related to the limited solubility of Sc on the Sr site of the perovskite lattice of ST.

    Se sintetizaron materiales cerámicos de titanato de estroncio dopado con escandio mediante reacción en estado sólido De acuerdo a la composición Sr1-1.5xScxTiO3 con x= 0-0.1. Las propiedades estructurales y el desarrollo microestructural se estudiaron mediante XRD y SEM. La propiedades dieléctricas se estudiaron como función de la temperatura y de la frecuencia en el rango de la frecuencias de radio. Se observó que los parámetros de red, la densidad y el tamaño del grano disminuyen ligeramente con el contenido en Sc. La permitividad dieléctrica y las perdidas también disminuyen. El dopado con Sc tiene un efecto muy ligero sobre el comportamiento paraeléctrico cuántico del titanato de estroncio y no se observó anomalías dioeléctricas , lo que está probablemente relacionado con la baja solubilidad del Sc en posiciones del Sr en la estructura tipo perovskita del titanato de estroncio.

  7. Development of nondestructive evaluation methods for structural ceramics

    International Nuclear Information System (INIS)

    Ellingson, W.A.; Roberts, R.A.; Vannier, M.W.; Ackerman, J.L.; Sawicka, B.D.; Gronemeyer, S.; Kriz, R.J.

    1987-01-01

    Advanced nondestructive evaluation methods are being developed to characterize ceramic materials and allow improvement of process technology. If one can spatially determine porosity, map organic binder/plasticizer distributions, measure average through-volume and in-plane density, as well as detect inclusions, process and machining operations may be modified to enhance the reliability of ceramics. Two modes of X-ray tomographic imaging -- advanced film (analog) tomography and computed tomography -- are being developed to provide flaw detection and density profile mapping capability. Nuclear magnetic resonance imaging is being developed to determine porosity and map the distribution of organic binder/plasticizer. Ultrasonic backscatter and through-transmission are being developed to measure average through-thickness densities and detect surface inclusions

  8. Structural characterization of clays commercially used in red ceramics

    International Nuclear Information System (INIS)

    Brito, E.M.; Moura, J.K.L.; Souza, R.B.; Brandim, A.S.

    2014-01-01

    The use of clays hills being an alternative to clay floodplain, due to environmental protection laws. The research project aims at the morphological and chemical characterization of hills clays used industrially for the production of ceramic tiles and blocks. Therefore, two types of methods were known commercially in the region of Teresina-PI through diffraction of X-rays (X-DR), scanning electron microscopy (SEM) and energy dispersive spectrometry X-ray (EDS). It can be observed that the samples have a high percentage of quartz, hematite still having in its constitution aluminum oxide, zirconium oxide and titanium oxide. The results show that the clays are clays and montmorillonites may be used for the production of ceramic tiles and blocks, but as the proportion of using the same will be focusing the next job. (author)

  9. A-Site (MCe) Substitution Effects on the Structures and Properties of CaBi4Ti4O15 Ceramics

    Science.gov (United States)

    Yan, Haixue; Li, Chengen; Zhou, Jiaguang; Zhu, Weimin; He, Lianxin; Song, Yuxin

    2000-11-01

    We investigated the effect of A-site compound substitution on the structures and properties of Ca0.8(MCe)0.1Bi4Ti4O15 (M denotes Li, Na and K) ceramics. The samples were prepared by the conventional ceramic technique. Sintering characteristics of Ca0.8(MCe)0.1Bi4Ti4O15 and CaBi4Ti4O15 ceramics were discussed. X-ray powder diffraction patterns of the three modified CBT-based compounds show a single phase of bismuth oxide layer type structure with m=4. The hysteresis loops of polarization versus electric field of the four compounds were also measured. A-site compound substitution improves the piezoelectric properties and the high-temperature resistivity of these materials. A-site (LiCe) and (KCe) substitution not only improves the Curie temperature but also decreases the temperature coefficient of dielectric constant (TK\\varepsilon). Among the three modified ceramics, only the Curie temperature of Ca0.8(NaCe)0.1Bi4Ti4O15 is lower than that of CaBi4Ti4O15; however, its TK\\varepsilon is the lowest. As a result, all the three modified CBT-based ceramics were found to be excellent high-temperature piezoelectric materials.

  10. Dynamic crack arrest in ceramics and ceramic composites

    Science.gov (United States)

    Kobayashi, A. S.; Yang, K. H.

    1989-01-01

    The results of past dynamic crack arrest experiments involving structural ceramics and ceramic composites are reviewed and analyzed. The lack of dynamic crack arrest in very brittle materials is discussed and contrasted with dynamic crack arrest in somewhat brittle metallic and polymeric materials. Numerical analyses show that the lack of crack arrest is due to reduced dynamic fracture resistance of the material and is not due to the kinetic energy.

  11. Edge chipping resistance and flexural strength of polymer infiltrated ceramic network and resin nanoceramic restorative materials.

    Science.gov (United States)

    Argyrou, Renos; Thompson, Geoffrey A; Cho, Seok-Hwan; Berzins, David W

    2016-09-01

    Two novel restorative materials, a polymer infiltrated ceramic network (PICN) and a resin nanoceramic (RNC), for computer-assisted design and computer-assisted manufacturing (CAD-CAM) applications have recently become commercially available. Little independent evidence regarding their mechanical properties exists to facilitate material selection. The purpose of this in vitro study was to measure the edge chipping resistance and flexural strength of the PICN and RNC materials and compare them with 2 commonly used feldspathic ceramic (FC) and leucite reinforced glass-ceramic (LRGC) CAD-CAM materials that share the same clinical indications. PICN, RNC, FC, and LRGC material specimens were obtained by sectioning commercially available CAD-CAM blocks. Edge chipping test specimens (n=20/material) were adhesively attached to a resin substrate before testing. Edge chips were produced using a 120-degree, sharp, conical diamond indenter mounted on a universal testing machine and positioned 0.1 to 0.7 mm horizontally from the specimen's edge. The chipping force was plotted against distance to the edge, and the data were fitted to linear and quadratic equations. One-way ANOVA determined intergroup differences (α=.05) in edge chipping toughness. Beam specimens (n=22/material) were tested for determining flexural strength using a 3-point bend test. Weibull statistics determined intergroup differences (α=.05). Flexural modulus and work of fracture were also calculated, and 1-way ANOVA determined intergroup differences (α=.05) RESULTS: Significant (Pmaterials for the 4 mechanical properties. Specifically, the material rankings were edge chipping toughness: RNC>LRGC=FC>PICN; flexural strength: RNC=LRGC>PICN>FC; flexural modulus: RNCLRGC=PICN>FC. The RNC material demonstrated superior performance for the mechanical properties tested compared with the other 3 materials. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All

  12. Comparison of fracture resistance of teeth restored with ceramic inlay and resin composite: an in vitro study.

    Science.gov (United States)

    Desai, Priti D; Das, Utapal Kumar

    2011-01-01

    The aim of this study was to evaluate the in vitro fracture resistance of teeth restored with bonded ceramic inlay and direct composite resin restoration in comparison to the normal tooth. This study evaluated the fracture strength of the teeth restored with bonded ceramic inlay and direct composite resin restoration in comparison to the normal teeth. Thirty intact human maxillary first premolars were assigned to three groups: Group 1 - comprising sound/unprepared teeth (control). Group 2 - comprising of Class-II direct composite resin restored teeth and Group 3 - comprising Class-II ceramic inlay restored teeth. Cavities were prepared with occlusal width of 1/3 intercuspal distance and 2 mm deep pulpally. Group 2 teeth were restored with hybrid composite resin (Z350 3M ESPE, USA) and group 3 teeth were restored with Vitadur Alpha alumina (Ivoclare Vivadent, Liechtenstein, Europe). Ceramic inlay was bonded with adhesive cement (rely X resin cement of 3MESPE, USA). The specimens were subjected to a compressive load until they fractured. Data were analyzed statistically by unpaired Student's t test. The fracture resistant strength, expressed as kilonewton (KN), was group 1 - 1.51 KN, group 2 - 1.25 KN, and group 3 - 1.58 KN. Statistically, group III had highest fracture resistance followed by group I, while group II had the lowest average fracture resistance. The fracture resistant strength of teeth restored with ceramic inlay was comparable to that of the normal intact teeth or slightly higher, while teeth restored with direct composite resin restoration showed less fracture resistant strength than that of the normal teeth.

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

    Directory of Open Access Journals (Sweden)

    Mitić V.V.

    2013-01-01

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

  14. Heat-Resistant Ceramic Pigments on the Base of Waste Vanadium Catalyst and Alumina

    OpenAIRE

    M. B. Sedelnikova; N. V. Liseenko; Y. I. Pautova; V. M. Pogrebenkov

    2013-01-01

    Ceramic pigments on the base of technogenic silica-containing material—waste vanadium catalyst were obtained in this work. Corundum is identified along with the predominant mullite phase in the composition of pigments. The ions of nickel, chromium, and iron are embedded in the structure if the concentration of the corresponding oxide in the initial mixture does not exceed 10 wt.%. In this case, the oxide is not identified in a free form according to the results of X-ray diffraction analysis. ...

  15. Change of sheet resistance of high purity alumina ceramics implanted by Cu and Ti ions

    International Nuclear Information System (INIS)

    Li Dexing; Zhang Jizhong; Yu Miao; Kang Jianchang; Li Wenzhi

    2005-01-01

    High purity alumina ceramics (99% Al 2 O 3 ) was implanted by copper ion and titanium ion in a metal vapour vacuum arc (MEVVA) implanter, respectively. The influence of implantation parameters was studied varying ion fluence. The samples were implanted by 68 keV Cu ion and 82 keV Ti ion with fluences from 1 x 10 15 to 1 x 10 18 ions/cm 2 , respectively. The as-implanted samples were investigated by scanning electron microscopy (SEM), glancing X-ray diffraction (GXRD), scanning Auger microscopy (SAM), and four-probe method. Different morphologies were observed on the surfaces of the as-implanted samples and clearly related to implantation parameters. For both ion implantations, the sheet resistances of the alumina samples implanted with Cu and Ti ion fluences of 1 x 10 18 ions/cm 2 , respectively, reached the corresponding minimum values because of the surface metallization. The experimental results indicate that the high-fluence ion implantation resulted in conductive layer on the surface of the as-implanted high purity alumina ceramics

  16. Fire resistance of structural composite lumber products

    Science.gov (United States)

    Robert H. White

    2006-01-01

    Use of structural composite lumber products is increasing. In applications requiring a fire resistance rating, calculation procedures are used to obtain the fire resistance rating of exposed structural wood products. A critical factor in the calculation procedures is char rate for ASTM E 119 fire exposure. In this study, we tested 14 structural composite lumber...

  17. 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.

  18. Thermal shock resistance behavior of a functionally graded ceramic: Effects of finite cooling rate

    Directory of Open Access Journals (Sweden)

    Zhihe Jin

    2014-01-01

    Full Text Available This work presents a semi-analytical model to explore the effects of cooling rate on the thermal shock resistance behavior of a functionally graded ceramic (FGC plate with a periodic array of edge cracks. The FGC is assumed to be a thermally heterogeneous material with constant elastic modulus and Poisson's ratio. The cooling rate applied at the FGC surface is modeled using a linear ramp function. An integral equation method and a closed form asymptotic temperature solution are employed to compute the thermal stress intensity factor (TSIF. The thermal shock residual strength and critical thermal shock of the FGC plate are obtained using the SIF criterion. Thermal shock simulations for an Al2O3/Si3N4 FGC indicate that a finite cooling rate leads to a significantly higher critical thermal shock than that under the sudden cooling condition. The residual strength, however, is relatively insensitive to the cooling rate.

  19. Structural and electrical properties of microwave processed Ag modified KNN-LS ceramics.

    Science.gov (United States)

    Palei, Prakash; Kumar, Pawan; Agrawal, Dinesh K

    2012-01-01

    Microwave processing steps of 0.95[(K0.5Na0.5)0.94Ag0.06NbO3]-0.05[LiSbO3]/(KNAN-LS) lead free ferroelectric ceramics were optimized for better densification and electrical properties. Calcination temperature and time for single perovskite phase formation were optimized and found to be 850 degrees C for 60 min., respectively. Crystal structural study revealed the presence of mixed structure in the microwave processed (MWP) KNAN-LS ceramics. The sintering of the KNAN-LS ceramics was carried out at 1080 degrees C for 10 min, 20 min and 30 min, respectively, and the sample sintered for 20 min exhibited best properties.

  20. Structure-terahertz property relationship in yttrium aluminum garnet ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Steere, D.W.; Clark, B.M.; Sundaram, S.K. [Alfred University, Terahertz and Millimeter Waves Laboratory (T-Lab), Kazuo Inamori School of Engineering, The New York State College of Ceramics, Alfred, NY (United States); Gaume, R. [Townes Laser Institute and the NanoScience Technology Center, CREOL, The College of Optics and Photonics, Orlando, FL (United States)

    2017-08-15

    Terahertz (THz) transmission measurements on chemically variant yttrium aluminum garnet (YAG) ceramics are described. Chemical compositions and processing parameters were varied to determine the effect of stoichiometry, density, and pore volume distribution on the optical and dielectric properties in the THz frequency regime. Density has the largest effect on properties out of the parameters that were investigated. In addition, a linear correlation between cubic root of real permittivity at 1 THz and average density of these samples is observed. Our results show promise for design and fabrication of advanced optical materials and devices with desired THz properties via controlling density and porosity of the materials. (orig.)

  1. Comparative study of the structural damage of nano-structured and micro-structured ceramics SiC under irradiation

    International Nuclear Information System (INIS)

    Leconte, Y.; Herlin-Boime, N.; Reynaud, C.; Monnet, I.; Levalois, M.; Morales, M.; Portier, X.; Thome, L.

    2006-01-01

    In order to know if the nano-structured ceramics SiC are possible materials for the future nuclear applications, SiC pellets have been submitted to low and mean energy irradiation experiments. These samples have been characterized by grazing X-ray diffraction and confocal Raman spectroscopy as well as conventional SiC ceramic pellets as reference. The low energy irradiations have allowed to exceed the amorphization threshold and to obtain a total disorder in the two types of samples. At the mean energies, this amorphization has not been obtained in spite of the doses generating a number of dpa superior to those of the low energies. The hypothesis of a synergy between the effects of the electronic and nuclear energy losses is advanced. (O.M.)

  2. Porous ceramics out of oxides

    International Nuclear Information System (INIS)

    Bakunov, V.S.; Balkevich, V.L.; Vlasov, A.S.; Guzman, I.Ya.; Lukin, E.S.; Poluboyarinov, D.N.; Poliskij, R.Ya.

    1977-01-01

    A review is made of manufacturing procedures and properties of oxide ceramics intended for high-temperature thermal insulation and thermal protection applications. Presented are structural characteristics of porous oxide refractories and their properties. Strength and thermal conductivity was shown to depend upon porosity. Described is a procedure for manufacturing porous ceramic materials from aluminium oxide, zirconium dioxide, magnesium oxide, beryllium oxide. The thermal resistance of porous ceramics from BeO is considerably greater than that of other high-refractoriness oxides. Listed are areas of application for porous materials based on oxides

  3. The impact of core-shell nanotube structures on fracture in ceramic nanocomposites

    International Nuclear Information System (INIS)

    Liang, Xin; Yang, Yingchao; Lou, Jun; Sheldon, Brian W.

    2017-01-01

    Multi-wall carbon nanotubes (MWCNTs) can be used to create ceramic nanocomposites with improved fracture toughness. In the present work, atomic layer deposition (ALD) was employed to deposit thin oxide layers on MWCNTs. These core-shell structures were then used to create nanocomposites by using a polymer derived ceramic (PDC) to produce the matrix. Variations in both the initial MWCNT structure and the oxide layers led to substantial differences in fiber-pullout behavior. Single tube pullout tests also showed that the oxide coatings led to stronger bonding with the ceramic matrix. With high defect density MWCNTs, this led to shorter pull-out lengths which is consistent with the conventional understanding of fracture in ceramic matrix composites. However, with low defect density MWCNTs longer pullout lengths were observed with the oxide layers. To interpret the different trends that were observed, we believe that the ALD coatings should not be viewed simply as a means of altering the interfacial properties. Instead, the coated MWCNTs should be viewed as more complex core-shell fibers where both interface and internal properties can be controlled with the ALD layers. - Graphical abstract: Fracture properties of core-shell nanotubes reinforced ceramic nanocomposites.

  4. In vitro comparative analysis of resistance to compression of laboratory resin composites and a ceramic system

    Directory of Open Access Journals (Sweden)

    Montenegro Alexandre

    2010-01-01

    Full Text Available Background: Restorative materials must be capable not only of restoring the patient′s masticatory function, but also to rescue the self-esteem of those maculated by a disharmonious smile. Among the esthetic materials available on the market, the choice frequently lies between ceramic or indirect laboratory resin restorations. Aim: This study assessed the resistance to compression of two laboratory resins found on the market, namely Artglass ® and Targis ® , considering Omega 900 ® ceramic from Vita as control. Materials and Methods: With the aid of stainless steel matrices, with internal dimensions of 8.0 mm diameter at the base, 9.0 mm in the top portion and 4.0 mm height, 15 test specimens were made, being 5 of each material to be tested. The test specimens were kept in distilled water for 72 hours and submitted to an axial load by the action of a point with a rounded tip 2 mm in diameter, adapted to an EMIC 500 universal test machine. The compression speed was 0.5 mm/min, with a load cell capacity of 200 Kgf. Results: The means of the results were calculated in kilogram-force (Kgf. The results found were treated by analysis of variance (ANOVA and the differences found among the groups were identified by the Tukey test (5%. Conclusion: It was observed that the material Omega 900 ® offered significantly greater resistance to compression than the other two materials, which did not present statistically significant difference between them.

  5. Comparison of thermal analysis, micro structural and compositional of archaeological indigenous ceramic (Caninhas site of Canas - SP) with actual clay/ceramic of region

    International Nuclear Information System (INIS)

    Nakano, F.P.; Taguchi, S.P.; Matos, C.C.; Ribeiro, R.B.

    2009-01-01

    The ceramic material found at the archaeological site in Caninhas, shows funerary structures of combustion and various objects of Tupi-Guarani indigenous use. These pieces and fragments were saved and cataloged, in approximately 4000 units. The ceramics present a gradient of color, from ochre to dark gray, when from the surface to the center of the piece, indicating compositional variation caused by inefficient sintering carried out by indigenous people. The goal of this study was to observe the phase transition temperature, decomposition, mass variation and reactions that occur in the archaeological and nowadays ceramics (by DSC/TG), together with micro structural analysis (by SEM), phase analysis (by XRD) and chemical composition (by EDS). Ceramics nowadays are sintered with air, in a temperature ranging between 400-800 °C for one hour, and presents heterogeneous microstructure. The archaeological ceramics were identified by the illite, hydrated alumina, lutecite and quartz phase, and the caulinite, lutecite and quartz phase in clay produced today from that region differs in all characteristics and aspects according to time. The interaction between different areas of expertise is fundamental to aggregate knowledge: the use of ceramic material engineering to archaeological application. (author)

  6. Comparison of thermal analysis, micro structural and compositional of archaeological indigenous ceramic (Caninhas site of Canas - SP) with actual clay/ceramic of region

    Energy Technology Data Exchange (ETDEWEB)

    Nakano, F.P.; Taguchi, S.P.; Matos, C.C.; Ribeiro, R.B., E-mail: japaum@alunos.eel.usp.br, E-mail: simone@demar.eel.usp.br, E-mail: cristhian@alunos.eel.usp.br, E-mail: baptistan@demar.eel.usp.br [Universidade de Sao Paulo (DEMAR/EEL/USP), Lorena, SP (Brazil). Escola de Engenharia. Departamento de Materiais; Rosa, S.J.L., E-mail: sarinhaleone@gmail.com [Centro Universitario de Volta Redonda, Volta Redonda, RJ (Brazil)

    2009-07-01

    The ceramic material found at the archaeological site in Caninhas, shows funerary structures of combustion and various objects of Tupi-Guarani indigenous use. These pieces and fragments were saved and cataloged, in approximately 4000 units. The ceramics present a gradient of color, from ochre to dark gray, when from the surface to the center of the piece, indicating compositional variation caused by inefficient sintering carried out by indigenous people. The goal of this study was to observe the phase transition temperature, decomposition, mass variation and reactions that occur in the archaeological and nowadays ceramics (by DSC/TG), together with micro structural analysis (by SEM), phase analysis (by XRD) and chemical composition (by EDS). Ceramics nowadays are sintered with air, in a temperature ranging between 400-800 °C for one hour, and presents heterogeneous microstructure. The archaeological ceramics were identified by the illite, hydrated alumina, lutecite and quartz phase, and the caulinite, lutecite and quartz phase in clay produced today from that region differs in all characteristics and aspects according to time. The interaction between different areas of expertise is fundamental to aggregate knowledge: the use of ceramic material engineering to archaeological application. (author)

  7. Effect of different glass and zeolite A compositions on the leach resistance of ceramic waste forms

    International Nuclear Information System (INIS)

    Lewis, M.A.; Hash, M.; Glandorf, D.

    1996-01-01

    A ceramic waste form is being developed for waste generated during electrometallurgical treatment of spent nuclear fuel. The waste is generated when fission products are removed from the electrolyte, LiCl-KCl eutectic. The waste form is a composite fabricated by hot isostatic pressing a mixture of glass frit and zeolite occluded with fission products and salt. Normalized release rate is less than 1 g/m 2 d for all elements in MCC-1 leach test run for 28 days in deionized water at 90 C. This leach resistance is comparable to that of early Savannah River glasses. We are investigating how leach resistance is affected by changes in cationic form of zeolite and in glass composition. Composites were made with 3 forms of zeolite A and 6 glasses. We used 3-day ASTM C1220-92 (formerly MCC-1) leach tests to screen samples for development purposes only. The leach test results show that the glass composites of zeolites 5A and 4A retain fission products equally well. Loss of Cs is small (0.1-0.5 wt%), while the loss of divalent and trivalent fission products is one or more orders of magnitude smaller. Composites of 5A retain chloride ion better in these short-term screens than 4A and 3A. The more leach resistant composites were made with durable glasses rich in silica and poor in alkaline earth oxides. XRD show that a salt phase was absent in the leach resistant composites of 5A and the better glasses but was present in the other composites with poorer leach performance. Thus, absence of salt phase corresponds to improved leach resistance. Interactions between zeolite and glass depend on composition of both

  8. Fracture mechanical investigations about crack resistance behaviour in non-transforming ceramics in particular aluminum oxide

    International Nuclear Information System (INIS)

    Baer, K.K.O.; Kleist, G.; Nickel, H.

    1991-03-01

    The aim of this work is the clearification of R-curve behaviour of non-transforming ceramics, in particular aluminum oxide exhibiting incrystalline fracture. Investigations of crack growth in controlled bending experiments were performed using 3-Pt- and 4-Pt-bending samples of differing sizes under inert conditions. The fracture experiments were realized using several loading techniques, for example constant and varying displacement rates, load rupture (P = 0) and relaxation tests (v = 0). In addition unloading and reloading experiments were performed to investigate hysteresis curves and residual displacements in accordance with R-curve behaviour. During the crack-growth experiments, the crack extension was measured in situ using a high resolution immersion microscope. With this technique, the fracture processes near the crack tip (crack activity zone) was observed as well. The crack resistance as a function of crack extension (R-curve) was determined using differing calculation methods. All of the methods used resulted in approximately identical R-curves, within the statistical error band. The crack resistance at initiation R 0 was 20 N/m. The crack resistance increased during approximately 3 mm of growth to a maximum of 90 N/m. A decrease in the crack resistance was determined for large a/W (crack length normalized with sample height) values, independant of the calculation methods. The R-curve behaviour was interpreted as due to a functional resistance behind the observed crack tip, which arises from a volume dilatation in the crack activity zone while the crack proceeds. (orig.) [de

  9. Equivalent resistors of polyhedral resistive structures

    NARCIS (Netherlands)

    van Steenwijk, FJ

    The equivalent resistors of regular polyhedral resistive structures between any two of the vertices are calculated in terms of the characteristic properties of the structures. Some special cases are considered. (C) 1998 American Association of Physics Teachers.

  10. Thermal resistance of buffer layer in a ceramic wall of MHD generation channel

    International Nuclear Information System (INIS)

    Nomura, Osami; Ebata, Yoshihiro; Hijikata, Kenichi.

    1982-01-01

    A wal l model is composed for obtaining the thermal resistance of the buffer layer. A buffer layer of the model is consisted to an adhesive layer and a buffer body. The adhesive layer is made of a copper plate, which is 0.3 mm thick, and adhered to the element by Refractory Method. The adhesive layer is consisted to three layers, i.e., Cu, Cu 2 O and CuO. These three layers seems to give rise to the thermal resistance. The buffer body is made of nickel wires of which radious is 0.4 mm and purity is 99.7%. All of the nickel wires are assembled in one direction which is parallel to a center line of the element, and bundled all together. Occupation ratio of nickel is about 78% in a sectional area of the buffer body. One end of the buffer body is soldered to adhesive layer by silver solder and opposite and is soldered to holder by lead solder. An element of the model is made of magnesia ceramics of which purity is about 99.9% and porosity is about 3%. A holder of the model is made of copper block. Results are as follows: (1) Thermal resistance of the buffer layer is from 1.9 to 2.5K/(W/cm 2 ). (2) Thermal resistance of the adhesive layer is from 0.43 to 0.87K/(W/cm 2 ). (3) Thermal resistance of the buffer body is calculated to about 0.7K/(W/cm 2 ) under the estimation at which the heat flows in the nickel wires only. (4) From above results, thermal resistance of silver soldering layer seems to be same as that of the adhesive layers. The buffer layer needs more value of the thermal resistance in order to apply to the MHD generation channel. Value of the thermal resistance is easily satisfied by changing of material of the buffer body, increase of thickness of the buffer layer and etc. Then this wall appears to be useful to an MHD generation channel wall. (author)

  11. The Influence of Tool Composite's Structure During Process of Diamond Grinding of Ceramic Materials

    Directory of Open Access Journals (Sweden)

    Gawlik Józef

    2014-12-01

    Full Text Available This paper presents the results of the tests performed during the grinding process of the ceramic materials: – polycrystalline ceramics (Zirconium ZrO2 and mono-crystalline ceramics (sapphire α-Al2O3 by the diamond tools. Studies have shown that the concentration (thickening of the tool composite changes the tool's pore structure when using suitable wetted adamantine additives. Such modified composite has positive impact on tribological properties of the subsurface layer of the machined components. This is manifested by the reduction of the surface roughness and reduction of the vibration amplitude of the coefficient of friction. The possibilities of the positive effects when using wetted additives on the tool's composite during the pressing (briquetting stage confirm the study results.

  12. Novel zirconia powder products for the structural ceramics industry

    International Nuclear Information System (INIS)

    Barnett, G.H.; Hartshorn, A.J.

    1988-01-01

    Two new zirconia powder products, SY-ULTRA and SYP-ULTRA, were developed to produce advanced engineering ceramics components of high strength and toughness. These characteristics are reflected in the SY-ULTRA microstructure which shows that there is an absence of cubic grains between 1300 degrees C and 1500 degress C, resulting from the high uniformity of yttria distribution throughout the powder. SYP-ULTRA gives excellent green densities while maintaining outstanding sintering performances and therefore gives rise to less shrinkage. Compressive and flexural strengths are high and controllable. Moreover, the technology allows that characteristics such as surface area, particle size and yttria levels can be modified to suit particular needs. Performance characteristics of the new products are tabulated and a comparison is made with other commercially available zirconia powders. 4 figs, 3 tabs

  13. Structural and Thermomechanical Properties of Stove Tile Ceramics

    Directory of Open Access Journals (Sweden)

    Anton TRNÍK

    2013-12-01

    Full Text Available The thermomechanical and thermodilatometric behavior of fired heatproof stove tile ceramic material Letovice, which contains quartz, mullite and small amounts of feldspar and glassy phase, was studied while increasing temperature up to 1100 °C. Young’s modulus was measured using the non-destructive sonic resonant method mf-TMA. To find actual dimensions of the sample, thermodilatometry was carried out at the same temperature regime as mf-TMA. A significant increase in Young’s modulus was observed in the region of the α ® b transformation of quartz. This can be explained by the healing effect of the induced radial stresses around the quartz grains on microcracks. The presence of glassy phase caused a small decrease of Young’s modulus at temperatures above ~950 °C. DOI: http://dx.doi.org/10.5755/j01.ms.19.4.2916

  14. 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.

  15. An Harmonic Smile Resulted from the Use of Ceramic Prosthesis with Zirconia Structure: A Case Report

    Science.gov (United States)

    Tavarez, Rudys Rodolfo de Jesus; Goncalves, Leticia Machado; Dias, Ana Paula; Dias, Anna Claudia Pereira; Malheiros, Adriana Santos; Silva, Alice Carvalho; Bandeca, Matheus Coelho

    2014-01-01

    The rehabilitation of patients requiring an esthetic smile demands a multidisciplinary approach. This clinical report describes a treatment plan for recovery aesthetics’ smile of anterior teeth using ceramic prosthesis with zirconia structure. Initially, a review of aesthetic parameters, diagnostic waxing, mock-up and provisional restorations was performed. A contextual assessment of aesthetic, proportion and shape of teeth was done to recreate a natural looking for teeth in consonance with the smile line. Subsequently, based on these parameters, fixed prostheses of the upper anterior teeth using ceramic restorations with zirconia infrastructures were performed. The use of ceramic restorations with zirconia structures associated with a careful treatment plan allows the professional to integrate esthetic and function for satisfactory clinical results. How to cite the article: Tavarez RR, Gonçalves LM, Dias AP, Dias AC, Malheiros AS, Silva AC, Bandeca MC. An harmonic smile resulted from the use of ceramic prosthesis with zirconia structure: A case report. J Int Oral Health 2014;6(3):90-2. PMID:25083040

  16. A novel highly porous ceramic foam with efficient thermal insulation and high temperature resistance properties fabricated by gel-casting process

    Science.gov (United States)

    Yu, Jiahong; Wang, Guixiang; Tang, Di; Qiu, Ya; Sun, Nali; Liu, Wenqiao

    2018-01-01

    The design of super thermal insulation and high-temperature resistant materials for high temperature furnaces is crucial due to the energy crisis and the huge wasting. Although it is told that numerous studies have been reported about various of thermal insulation materials prepared by different methods, the applications of yttria-stabilized zirconia (YSZ) ceramic foams fabricated through tert-butyl alcohol (TBA)-based gel-casting process in bulk thermal isolators were barely to seen. In this paper, highly porous yttria-stabilized zirconia (YSZ) ceramic foams were fabricated by a novel gel-casting method using tert-butyl alcohol (TBA) as solvent and pore-forming agent. Different raw material ratio, sintering temperature and soaking time were all investigated to achieve optimal thermal insulation and mechanical properties. We can conclude that porosity drops gradually while compressive strength increases significantly with the rising temperature from 1000-1500°C. With prolonged soaking time, there is no obvious change in porosity but compressive strength increases gradually. All specimens have uniformly distributed pores with average size of 0.5-2μm and show good structural stability at high temperature. The final obtained ceramic foams displayed an outstanding ultra-low thermal conductivity property with only 200.6 °C in cold surface while the hot side was 1000 °C (hold 60 min to keep thermal balance before testing) at the thickness of 10 mm.

  17. 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.

  18. Three-dimensional pore structure and ion conductivity of porous ceramic diaphragms

    OpenAIRE

    Wiedenmann, Daniel; Keller, Lukas; Holzer, Lorenz; Stojadinović, Jelena; Münch, Beat; Suarez, Laura; Fumey, Benjamin; Hagendorfer, Harald; Brönnimann, Rolf; Modregger, Peter; Gorbar, Michal; Vogt, Ulrich F.; Züttel, Andreas; Mantia, Fabio La; Wepf, Roger

    2013-01-01

    The ion conductivity of two series of porous ceramic diaphragms impregnated with caustic potash was investigated by electrochemical impedance spectroscopy. To understand the impact of the pore structure on ion conductivity, the three-dimensional (3-D) pore geometry of the diaphragms was characterized with synchrotron x-ray absorption tomography. Ion migration was calculated based on an extended pore structure model, which includes the electrolyte conductivity and geometric pore parameters, fo...

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

    International Nuclear Information System (INIS)

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

    1997-08-01

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

  20. Residual stress distribution of the soldered structure with Kovar alloy and Al2O3 ceramics

    Directory of Open Access Journals (Sweden)

    Qile Gao

    2017-03-01

    Full Text Available Residual stress distribution in soldered structure of Kovar alloy and Al2O3 ceramics was determined using XRD analyses. In order to measure the residual stress, position of the characteristic diffraction peak and stress constant were obtained using several versatile/advanced techniques after calibration. Residual stress of soldered structure was measured based on the diffraction patterns obtained for the distribution of residual stress in the soldered joint. Only diffraction peak at 149° for Kovar alloy and two diffraction peaks ranging from 140–170° for Al2O3 ceramics were found to be appropriate for the residual stress determination. It was also confirmed that for Al2O3 ceramics the XRD peak at 152° reflects the changes of stress more precisely than the one at 146°. The stress constant K of Kovar alloy and Al2O3 ceramics was found to be −197 MPa/° and −654 MPa/°, respectively. After soldering, the maximum residual stress of the soldered joint of both materials developed at 1 mm from the soldering seam, and the values within 3 mm from the soldering seam are generally significant. Thus, it is important to pay attention to the area of 3 mm from the soldering seam in practical application.

  1. Repair of pathology of structure with mortar to reject the red ceramics

    International Nuclear Information System (INIS)

    Santana, Claudeir de Souza; Santos, Juzelia

    2010-01-01

    The aim of this research is the use of the reject of red ceramic from an industry of bricks and tiles from the region of Cuiaba as mortar for repair of structural pathology, looking for their application to replace the sand and gravel in the process. The mortar produced restores a park bench made of concrete which seat was made of red ceramic and legs of soil-cement bricks. The reject of red ceramic used is from an industry in the region of Cuiaba, discarded at the end of the production process, ground in an appropriate granulometry to simulate a generic type of sand and gravel. Grinding processes were developed and various granulometric curves were drawned. The aggregates produced were characterized from the deposit until the final grinding according to ABNT norms in force, the specific area by BET, was used for microanalysis X-ray diffraction. ABNT standards were used to characterize and compare the results. The mortar produced proved to be adequate for the proposal restoration, it was consistent and cohesive. It was concluded that the mortar produced with recycled aggregate of red ceramic can be used in structural restoration in civil construction to replace the natural aggregate, with cost and environmental benefits. (author)

  2. Progress in the characterisation of structural oxide/oxide ceramic matrix composites fabricated by electrophoretic deposition (EPD)

    Czech Academy of Sciences Publication Activity Database

    Stoll, E.; Mahr, P.; Kruger, H. G.; Kern, H.; Dlouhý, Ivo; Boccaccini, A. R.

    2006-01-01

    Roč. 8, č. 4 (2006), s. 282-285 ISSN 1438-1656 R&D Projects: GA ČR(CZ) GA106/05/0495 Institutional research plan: CEZ:AV0Z20410507 Keywords : electorphoretic deposition * oxid/oxid ceramic matrix composites * flexural strength Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass Impact factor: 1.402, year: 2006 http://www3.interscience.wiley.com/cgi-bin/jissue/112579545

  3. Y5U multilayer ceramic capacitors with high-specific capacitance and low-equivalent series resistance.

    Science.gov (United States)

    Ochi, A; Mori, T; Nakanishi, M; Utsumi, K; Abe, S; Yoshimoto, T

    1991-01-01

    A dielectric powder material, for Y5U multilayer ceramic capacitors was developed in the Pb(Mg(1/3)Nb(2/3))O (3)-Pb(Ni(1/3)Nb(2/3))O(3)-PbTiO (3) ternary system by using an alkoxide process. Multilayer ceramic chip capacitors (10 muF) with high specific capacitances were fabricated using this powder. A Ag80%-Pd20% alloy was used for the internal electrodes. The alkoxide-derived capacitor had an extremely high specific capacitance of about 500 muF/cm(3) and a small temperature dependence meeting Y5U specifications of the EIA standard. The equivalent series resistance was approximately 20 mOmega at 500 kHz. The breakdown voltages of the capacitor were 300 V or higher. In accelerated load life tests and load humidity tests, no degradation of insulation resistance was found during 1000 h of testing.

  4. PPLICATION OF COAL MINING WASTE IN THE PRODUCTION OF STRUCTURAL CERAMICS USING AN ECOLOGICALLY FRIENDLY AND RESOURCE SAVING TECHNOLOGY

    Directory of Open Access Journals (Sweden)

    Vaysman Yakov Iosifovich

    2016-03-01

    Full Text Available The article states that the use of spoil heaps (coal mining waste in the production of structural ceramics is expedient. It shows the reduction of negative ecological effects during the life cycle when coal mining waste is used in the initial blend for the production of structural ceramics. It shows that the development of the recommendations for the use of coal mining waste in the production of structural ceramics is an urgent issue as far as the use of coal mining waste in the production of structural ceramics can lead both to the achievement of resource saving and positive ecological effect and to the undesirable decrease of the basic physical and mechanical properties of the final products when the structure of the mix is inappropriate. In order to develop these recommendations the authors have examined the microstructure, mineral composition and physical and mechanical properties of structural ceramics produced with the use of coal mining waste, which effect the consumer properties of the target material. As a result of the research the authors have made the conclusions about the nature and degree of impact of coal mining waste quantity on the physical and mechanical properties of construction ceramics. The comparison of the data received during the measurement of the basic physical and mechanical properties of construction ceramics with the results of the research of microstructure, elemental and mineral composition of the samples has shown their correlation.

  5. Structure and grain coarsening during the processing of engineering ceramics

    International Nuclear Information System (INIS)

    Shaw, N.J.

    1987-11-01

    Studies have been made of three ceramic systems (Al 2 O 3 , Y 2 O 3 /MgO, and SiC/C/B), both to explore a surface area/density diagram approach to examining the coarsening processes during sintering and to explore an alternative coarsening parameter, i.e., the grain boundary surface area (raising it at a given value of the density) and not the pore surface area; therefore, pinning of the grain boundaries by solid-solution drag is the only function evidenced by these results. The importance of such pinning even at densities as low as 75% of theoretical is linked to the existence of microstructural inhomogeneities. The early stages of sintering of Y 2 O 3 powder have been examined using two techniques, BET surface area analysis and transmission electron microscopy. Each has given some insight into the process occurring and, used together, have provided some indication of the effect of MgO on coarsening during sintering. Attempts to further elucidate effects of MgO on the coarsening behavior of Y 2 O 3 by the surface area/density diagram approach were unsuccessful due to masking effects of contaminating reactions during sintering and/or thermal etching. The behavior of the undoped SiC which only coarsens can be clearly distinguished by the surface area/density diagram from that of SiC/C/B which also concurrently densifies. Little additional information was obtainable by this method due to unfavorable sample etching characteristics. The advantages, disadvantages, and difficulties of application of these techniques to the study of coarsening during sintering are discussed

  6. Processing and characterization of ceramic superconductor/polymer composites

    International Nuclear Information System (INIS)

    Kander, R.G.; Namboodri, S.L.

    1993-01-01

    One way to more easily process a brittle high-temperature ceramic superconductor into a useful structure is to combine it with a polymer to form a composite material. Processing of polymer-based composites into complex shapes is well established and relatively easy when compared with traditional ceramic processing unit operations. In addition, incorporating a ceramic superconductor into a polymer matrix can improve mechanical performance as compared with a monolithic ceramic. Finally, because ceramic superconductors are susceptible to attack by moisture, a polymer-based composite structure can also provide protection from deleterious environmental effects. This paper focuses on the processing and subsequent characterization of ceramic superconductor/polymer composites designed primarily for electromagnetic shielding and diamagnetic applications. YBa 2 Cu 3 O 7-x [YBCO] ceramic superconductor is combined with poly(methyl methacrylate) [PMMA] to form novel composite structures. Composite structures have been molded with both a discontinuous superconducting phase (i.e., ceramic particulate reinforced polymers) and with a continuous superconducting phase (i.e., polymer infiltrated porous ceramics). Characterization of these composite structures includes the determination of diamagnetic strength, electromagnetic shielding effectiveness, mechanical performance, and environmental resistance. The goal of this program is to produce a composite structure with increased mechanical integrity and environmental resistance at liquid nitrogen temperatures without compromising the electromagnetic shielding and diamagnetic properties of the superconducting phase. Composites structures of this type are potentially useful in numerous magnetic applications including electromagnetic shielding, magnetic sensors, energy storage, magnetic levitation, and motor windings

  7. Cells responding to surface structure of calcium phosphate ceramics for bone regeneration.

    Science.gov (United States)

    Zhang, Jingwei; Sun, Lanying; Luo, Xiaoman; Barbieri, Davide; de Bruijn, Joost D; van Blitterswijk, Clemens A; Moroni, Lorenzo; Yuan, Huipin

    2017-11-01

    Surface structure largely affects the inductive bone-forming potential of calcium phosphate (CaP) ceramics in ectopic sites and bone regeneration in critical-sized bone defects. Surface-dependent osteogenic differentiation of bone marrow stromal cells (BMSCs) partially explained the improved bone-forming ability of submicron surface structured CaP ceramics. In this study, we investigated the possible influence of surface structure on different bone-related cells, which may potentially participate in the process of improved bone formation in CaP ceramics. Besides BMSCs, the response of human brain vascular pericytes (HBVP), C2C12 (osteogenic inducible cells), MC3T3-E1 (osteogenic precursors), SV-HFO (pre-osteoblasts), MG63 (osteoblasts) and SAOS-2 (mature osteoblasts) to the surface structure was evaluated in terms of cell proliferation, osteogenic differentiation and gene expression. The cells were cultured on tricalcium phosphate (TCP) ceramics with either micron-scaled surface structure (TCP-B) or submicron-scaled surface structure (TCP-S) for up to 14 days, followed by DNA, alkaline phosphatase (ALP) and quantitative polymerase chain reaction gene assays. HBVP were not sensitive to surface structure with respect to cell proliferation and osteogenic differentiation, but had downregulated angiogenesis-related gene expression (i.e. vascular endothelial growth factor) on TCP-S. Without additional osteogenic inducing factors, submicron-scaled surface structure enhanced ALP activity and osteocalcin gene expression of human (h)BMSCs and C2C12 cells, favoured the proliferation of MC3T3-E1, MG63 and SAOS-2, and increased ALP activity of MC3T3-E1 and SV-HFO. The results herein indicate that cells with osteogenic potency (either osteogenic inducible cells or osteogenic cells) could be sensitive to surface structure and responded to osteoinductive submicron-structured CaP ceramics in cell proliferation, ALP production or osteogenic gene expression, which favour bone

  8. Lithography-based ceramic manufacture (LCM) of auxetic structures: present capabilities and challenges

    International Nuclear Information System (INIS)

    Lantada, Andrés Díaz; De Blas Romero, Adrián; Schwentenwein, Martin; Jellinek, Christopher; Homa, Johannes

    2016-01-01

    Auxetic metamaterials are known for having a negative Poisson’s ratio (NPR) and for displaying the unexpected properties of lateral expansion when stretched and densification when compressed. Even though a wide set of micro-manufacturing resources have been used for the development of auxetic metamaterials and related devices, additional precision and an extension to other families of materials is needed for their industrial expansion. In addition, their manufacture using ceramic materials is still challenging. In this study we present a very promising approach for the development of auxetic metamaterials and devices based on the use of lithography-based ceramic manufacturing. The process stands out for its precision and complex three-dimensional geometries attainable, without the need of supporting structures, and for enabling the manufacture of ceramic auxetics with their geometry controlled from the design stage with micrometric precision. To our knowledge it represents the first example of application of this technology to the manufacture of auxetic geometries using ceramic materials. We have used a special three-dimensional auxetic design whose remarkable NPR has been previously highlighted. (paper)

  9. On the Mass Fractal Character of Si-Based Structural Networks in Amorphous Polymer Derived Ceramics

    Directory of Open Access Journals (Sweden)

    Sabyasachi Sen

    2015-03-01

    Full Text Available The intermediate-range packing of SiNxC4−x (0 ≤ x ≤ 4 tetrahedra in polysilycarbodiimide and polysilazane-derived amorphous SiCN ceramics is investigated using 29Si spin-lattice relaxation nuclear magnetic resonance (SLR NMR spectroscopy. The SiCN network in the polysilylcarbodiimide-derived ceramic consists predominantly of SiN4 tetrahedra that are characterized by a 3-dimensional spatial distribution signifying compact packing of such units to form amorphous Si3N4 clusters. On the other hand, the SiCN network of the polysilazane-derived ceramic is characterized by mixed bonded SiNxC4−x tetrahedra that are inefficiently packed with a mass fractal dimension of Df ~2.5 that is significantly lower than the embedding Euclidean dimension (D = 3. This result unequivocally confirms the hypothesis that the presence of dissimilar atoms, namely, 4-coordinated C and 3-coordinated N, in the nearest neighbor environment of Si along with some exclusion in connectivity between SiCxN4−x tetrahedra with widely different N:C ratios and the absence of bonding between C and N result in steric hindrance to an efficient packing of these structural units. It is noted that similar inefficiencies in packing are observed in polymer-derived amorphous SiOC ceramics as well as in proteins and binary hard sphere systems.

  10. On the Mass Fractal Character of Si-Based Structural Networks in Amorphous Polymer Derived Ceramics.

    Science.gov (United States)

    Sen, Sabyasachi; Widgeon, Scarlett

    2015-03-17

    The intermediate-range packing of SiN x C 4- x (0 ≤ x ≤ 4) tetrahedra in polysilycarbodiimide and polysilazane-derived amorphous SiCN ceramics is investigated using 29 Si spin-lattice relaxation nuclear magnetic resonance (SLR NMR) spectroscopy. The SiCN network in the polysilylcarbodiimide-derived ceramic consists predominantly of SiN₄ tetrahedra that are characterized by a 3-dimensional spatial distribution signifying compact packing of such units to form amorphous Si₃N₄ clusters. On the other hand, the SiCN network of the polysilazane-derived ceramic is characterized by mixed bonded SiN x C 4- x tetrahedra that are inefficiently packed with a mass fractal dimension of D f ~2.5 that is significantly lower than the embedding Euclidean dimension ( D = 3). This result unequivocally confirms the hypothesis that the presence of dissimilar atoms, namely, 4-coordinated C and 3-coordinated N, in the nearest neighbor environment of Si along with some exclusion in connectivity between SiC x N 4- x tetrahedra with widely different N:C ratios and the absence of bonding between C and N result in steric hindrance to an efficient packing of these structural units. It is noted that similar inefficiencies in packing are observed in polymer-derived amorphous SiOC ceramics as well as in proteins and binary hard sphere systems.

  11. Development of glass/glass-ceramics materials and devices and their micro-structural studies

    International Nuclear Information System (INIS)

    Goswami, Madhumita; Sarkar, Arjun; Shingarvelan, Shobha; Kumar, Rakesh; Ananathanarayan, Arvind; Shrikhande, V.K.; Kothiyal, G.P.

    2009-01-01

    Materials and devices based on glass and glass-ceramics (GCs) find applications in various high pressure and vacuum applications. We have prepared different glasses/glass-ceramics with requisite thermal expansion coefficient, electrical, vacuum and wetting characteristics to fabricate hermetic seals with different metals/alloys as well as components for these applications. Some of these are, SiO 2 -Na 2 O-K 2 O-Al 2 O 3 -B 2O3 (BS) for matched type of seal fabricated with Kovar alloy, SiO 2 -Na 2 O-K 2 O-BaO-PbO(LS) for fabrication of compressive type seals with stainless steel and SS 446 alloys, P 2 O 5 -Na 2 O-B 2 O 3 -BaO-PbO(NAP) for fabrication of matched type of seal with relatively low melting metals/alloys like AI/Cu-Be and Li 2 O-ZnO-SiO 2 -P 2 O 5 -B 2 O 3 -Na 2 O (LZS) and Lithium aluminium silicate (LAS) glass-ceramics to fabricate matched and compression types feedtroughs/conductivity probes Magnesium aluminium silicate (MAS) machinable glass-ceramics is another development for high voltage and ultra high vacuum applications. Micro-structural studies have been carried out on these materials to understand the mechanism of their behaviour and have also been deployed in various systems and plants in DAE. (author)

  12. Vibronic Jahn-Teller coupling and structural-systematic aspects of superconductivity in ceramic materials

    International Nuclear Information System (INIS)

    Reinen, D.

    1993-09-01

    The following subjects were mainly investigated: 1. Development of a concept concerning the mechanism of superconductivity in ceramic oxides from the standpoint of solid state chemistry. An important criterion for generating superconductivity in ceramic oxides seems to be the overlap of a narrow, weakly antibonding and metal-centred band with a very broad band of predominant oxygen character in the Fermi region. Spectroscopic investigations are in favour of such a concept and additionally indicate a vibronic coupling mechanism of the Jahn-Teller- or pseudo-Jahn-Teller type. 2. Synthesis of potentially superconducting ceramic oxides. A series of oxidic compounds with transition metal ions (Ni 2+ /Ni 3+ /Ni 4+ , Mn 3+ /Mn 4+ , Cu 2+ /Cu 3+ etc.) and with cations, possessing a lone electron pair (Sb 3+ , Bi 3+ , Pb 2+ , Tl + ) was prepared (K 2 NiF 4 -structure). The investigation of these ceramic materials led to interesting insight into the nature of the M-O-bond and the cooperative interactions between the metal ion centres; new superconductors could not be synthesized, however. (orig.) [de

  13. Sol–Gel-Derived Glass-Ceramic Photorefractive Films for Photonic Structures

    Directory of Open Access Journals (Sweden)

    Anna Lukowiak

    2017-02-01

    Full Text Available Glass photonics are widespread, from everyday objects around us to high-tech specialized devices. Among different technologies, sol–gel synthesis allows for nanoscale materials engineering by exploiting its unique structures, such as transparent glass-ceramics, to tailor optical and electromagnetic properties and to boost photon-management yield. Here, we briefly discuss the state of the technology and show that the choice of the sol–gel as a synthesis method brings the advantage of process versatility regarding materials composition and ease of implementation. In this context, we present tin-dioxide–silica (SnO2–SiO2 glass-ceramic waveguides activated by europium ions (Eu3+. The focus is on the photorefractive properties of this system because its photoluminescence properties have already been discussed in the papers presented in the bibliography. The main findings include the high photosensitivity of sol–gel 25SnO2:75SiO2 glass-ceramic waveguides; the ultraviolet (UV-induced refractive index change (Δn ~ −1.6 × 10−3, the easy fabrication process, and the low propagation losses (0.5 ± 0.2 dB/cm, that make this glass-ceramic an interesting photonic material for smart optical applications.

  14. Electrical resistivity and structure of liquid Ge

    International Nuclear Information System (INIS)

    Can, P.; Armagan, T.

    2002-01-01

    The static structure factors are considered as an important ingredient in the calculation of the electrical resistivity of liquid metals. In this work, the electrical resistivity for liquid Germanium is interpreted with the Zeeman formalism in terms of pseudopotential and structure factor within the framework of the Hasagewa - Watabe (HW) for the interionic interactions. The successes and failures of the Zeeman formula have been compared with the available experimental data

  15. A structural study of ceramic oxides by X-ray absorption spectroscopy

    International Nuclear Information System (INIS)

    Akhtar, M.J.

    1995-01-01

    A detailed structural study of ceramic oxides is presented by employing X-ray Absorption Spectroscopy (XAS). In the present work X-ray Absorption Near Edge Structure (XANES) is used for the investigation of valence state of metal cations; whereas, Extended X-ray Absorption Fine Structure EXAFS) is employed for the determination for bond lengths, coordination numbers and nature of the elements present in the near neighbour shells surrounding the absorbing atom. These results show that local environment of dopant and host cations are different; and this variation in local structure depends on the nature and concentration of the dopant ions. (author)

  16. Earthquake resistant design of structures

    International Nuclear Information System (INIS)

    Choi, Chang Geun; Kim, Gyu Seok; Lee, Dong Geun

    1990-02-01

    This book tells of occurrence of earthquake and damage analysis of earthquake, equivalent static analysis method, application of equivalent static analysis method, dynamic analysis method like time history analysis by mode superposition method and direct integration method, design spectrum analysis considering an earthquake-resistant design in Korea. Such as analysis model and vibration mode, calculation of base shear, calculation of story seismic load and combine of analysis results.

  17. Stochastic-Strength-Based Damage Simulation Tool for Ceramic Matrix and Polymer Matrix Composite Structures

    Science.gov (United States)

    Nemeth, Noel N.; Bednarcyk, Brett A.; Pineda, Evan J.; Walton, Owen J.; Arnold, Steven M.

    2016-01-01

    Stochastic-based, discrete-event progressive damage simulations of ceramic-matrix composite and polymer matrix composite material structures have been enabled through the development of a unique multiscale modeling tool. This effort involves coupling three independently developed software programs: (1) the Micromechanics Analysis Code with Generalized Method of Cells (MAC/GMC), (2) the Ceramics Analysis and Reliability Evaluation of Structures Life Prediction Program (CARES/ Life), and (3) the Abaqus finite element analysis (FEA) program. MAC/GMC contributes multiscale modeling capabilities and micromechanics relations to determine stresses and deformations at the microscale of the composite material repeating unit cell (RUC). CARES/Life contributes statistical multiaxial failure criteria that can be applied to the individual brittle-material constituents of the RUC. Abaqus is used at the global scale to model the overall composite structure. An Abaqus user-defined material (UMAT) interface, referred to here as "FEAMAC/CARES," was developed that enables MAC/GMC and CARES/Life to operate seamlessly with the Abaqus FEA code. For each FEAMAC/CARES simulation trial, the stochastic nature of brittle material strength results in random, discrete damage events, which incrementally progress and lead to ultimate structural failure. This report describes the FEAMAC/CARES methodology and discusses examples that illustrate the performance of the tool. A comprehensive example problem, simulating the progressive damage of laminated ceramic matrix composites under various off-axis loading conditions and including a double notched tensile specimen geometry, is described in a separate report.

  18. Influence of surface treatment on the in-vitro fracture resistance of zirconia-based all-ceramic anterior crowns.

    Science.gov (United States)

    Schmitter, M; Lotze, G; Bömicke, W; Rues, S

    2015-12-01

    The purpose of this study was to assess the effect of surface treatment on the fracture resistance of zirconia-based all-ceramic anterior crowns. Sixty-four zirconia-based all-ceramic anterior crowns, veneered by use of a press-on technique, were produced. For 48 crowns intraoral adjustment was simulated (A-group), 16 crowns remained unadjusted (WA-group). The adjusted area was then treated in three ways: 1. no further surface treatment; 2. polishing, with irrigation, using polishers interspersed with diamond grit for ceramics; and 3. polishing and glaze firing. Half of the specimens were loaded until fracture in an universal testing device without artificial ageing; the other crowns underwent thermocycling and chewing simulation before ultimate-load testing. Explorative statistical analysis was performed by use of non-parametric and parametric tests. In addition, fracture-strength tests according to ISO 6872 were performed for veneer ceramic subjected to the different surface treatments. Finite element analysis was also conducted for the crowns, and surface roughness was measured. Crowns in the A-group were more sensitive to aging than crowns in the WA-group (p=0.038). Although both polishing and glaze firing slightly improved the fracture resistance of the specimens, the fracture resistance in the WA-group (initial fracture resistance (IFR): 652.0 ± 107.7N, remaining fracture resistance after aging (RFR): 560.6 ± 233.3N) was higher than the fracture resistance in the A-group (polished: IFR: 477.9 ± 108.8N, RFR: 386.0 ± 218.5N; glaze firing: IFR: 535.5 ± 128.0N, RFR: 388.6 ± 202.2N). Surface roughness without adjustment was Ra=0.1 μm; for adjustment but without further treatment it was Ra=1.4 μm; for adjustment and polishing it was Ra=0.3 μm; and for adjustment, polishing, and glazing it was Ra=0.6 μm. Stress distributions obtained by finite element analysis in combination with fracture strength tests showed that fractures most probably originated from

  19. Preparation and Characterization of Nano-structured Ceramic Powders Synthesized by Emulsion Combustion Method

    International Nuclear Information System (INIS)

    Takatori, Kazumasa; Tani, Takao; Watanabe, Naoyoshi; Kamiya, Nobuo

    1999-01-01

    The emulsion combustion method (ECM), a novel powder production process, was originally developed to synthesize nano-structured metal-oxide powders. Metal ions in the aqueous droplets were rapidly oxidized by the combustion of the surrounding flammable liquid. The ECM achieved a small reaction field and a short reaction period to fabricate the submicron-sized hollow ceramic particles with extremely thin wall and chemically homogeneous ceramic powder. Alumina, zirconia, zirconia-ceria solid solutions and barium titanate were synthesized by the ECM process. Alumina and zirconia powders were characterized to be metastable in crystalline phase and hollow structure. The wall thickness of alumina was about 10 nm. The zirconia-ceria powders were found to be single-phase solid solutions for a wide composition range. These powders were characterized as equiaxed-shape, submicron-sized chemically homogeneous materials. The powder formation mechanism was investigated through the synthesis of barium titanate powder with different metal sources

  20. Structural investigations of Lu.sub.2./sub.O.sub.3./sub. as single crystal and polycrystalline transparent ceramic

    Czech Academy of Sciences Publication Activity Database

    Guzik, M.; Pejchal, Jan; Yoshikawa, A.; Ito, A.; Goto, T.; Siczek, M.; Lis, T.; Boulon, J.

    2014-01-01

    Roč. 14, č. 7 (2014), 3327 -3334 ISSN 1528-7483 Institutional support: RVO:68378271 Keywords : lutetium oxide * structure * crystal growth * ceramics Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 4.891, year: 2014

  1. Improved ferroelectric/piezoelectric properties and bright green/UC red emission in (Li,Ho)-doped CaBi4Ti4O15 multifunctional ceramics with excellent temperature stability and superior water-resistance performance.

    Science.gov (United States)

    Xiao, Ping; Guo, Yongquan; Tian, Mijie; Zheng, Qiaoji; Jiang, Na; Wu, Xiaochun; Xia, Zhiguo; Lin, Dunmin

    2015-10-21

    Multifunctional materials based on rare earth ion doped ferro/piezoelectrics have attracted considerable attention in recent years. In this work, new lead-free multifunctional ceramics of Ca1-x(LiHo)x/2Bi4Ti4O15 were prepared by a conventional solid-state reaction method. The great multi-improvement in ferroelectricity/piezoelectricity, down/up-conversion luminescence and temperature stability of the multifunctional properties is induced by the partial substitution of (Li0.5Ho0.5)(2+) for Ca(2+) ions in CaBi4Ti4O15. All the ceramics possess a bismuth-layer structure, and the crystal structure of the ceramics is changed from a four layered bismuth-layer structure to a three-layered structure with the level of (Li0.5Ho0.5)(2+) increasing. The ceramic with x = 0.1 exhibits simultaneously, high resistivity (R = 4.51 × 10(11)Ω cm), good piezoelectricity (d33 = 10.2 pC N(-1)), high Curie temperature (TC = 814 °C), strong ferroelectricity (Pr = 9.03 μC cm(-2)) and enhanced luminescence. These behaviours are greatly associated with the contribution of (Li0.5Ho0.5)(2+) in the ceramics. Under the excitation of 451 nm light, the ceramic with x = 0.1 exhibits a strong green emission peak centered at 545 nm, corresponding to the transition of the (5)S2→(5)I8 level in Ho(3+) ions, while a strong red up-conversion emission band located at 660 nm is observed under the near-infrared excitation of 980 nm at room temperature, arising from the transition of (5)F5→(5)I8 levels in Ho(3+) ions. Surprisingly, the excellent temperature stability of ferroelectricity/piezoelectricity/luminescence and superior water-resistance behaviors of piezoelectricity/luminescence are also obtained in the ceramic with x = 0.1. Our study suggests that the present ceramics may have potential applications in advanced multifunctional devices at high temperature.

  2. Procedure for the fabrication of ceramic fuel pellets with an adjustable structure

    International Nuclear Information System (INIS)

    Henke, M.; Klemm, U.; Sobek, D.

    1986-01-01

    The invention concerns a procedure for the fabrication of ceramic fuel pellets of UO 2 , PuO 2 , ThO 2 and their mixtures with an adjustable structure. Before or during the milling the particle shaped fuel pellets have been added polyethylenglycol in a 20 - 60 % aqueous solution with an amount of 0.5 - 2.0 % in weight. This additive has an effect on a controlled pore formation and grain growth advancement

  3. Ultimate strength of crystals, nanoparticles and nano-ceramics having diamond-like structure

    Directory of Open Access Journals (Sweden)

    Dora Zakarian

    2016-11-01

    Full Text Available A mathematical model for calculating the interplanar interaction energy of diamond-like structure ceramics at free surface of stock material in pseudopotential method has been developed. We have considered uniaxial [111] deformation of materials and obtained the “inverse Hall–Petch’s law” for strength. It is shown that nanoceramics has higher strength than the nanoparticles included in its composition.

  4. Flexural resistance of Cerec CAD/CAM system ceramic blocks. Part 2: Outsourcing materials.

    Science.gov (United States)

    Sedda, Maurizio; Vichi, Alessandro; Del Siena, Francesco; Louca, Chris; Ferrari, Marco

    2014-02-01

    To test different Cerec CAD/CAM system ceramic blocks, comparing mean flexural strength (sigma), Weibull modulus (m), and Weibull characteristic strength (sigma0) in an ISO standardized set-up. Following the recent ISO Standard (ISO 6872:2008), 11 types of ceramic blocks were tested: IPS e.max CAD MO, IPS e.max CAD LT and IPS e.max CAD HT (lithium disilicate glass-ceramic); In-Ceram SPINELL, In-Ceram Alumina and In-Ceram Zirconia (glass-infiltrated materials); inCoris AL and In-Ceram AL (densely sintered alumina); In-Ceram YZ, IPS e.max Zir-CAD and inCoris ZI (densely sintered zirconia). Specimens were cut out from ceramic blocks, finished, crystallized/infiltrated/sintered, polished, and tested in a three-point bending test apparatus. Flexural strength, Weibull characteristic strength, and Weibull modulus were obtained. A statistically significant difference was found (P ceramic (sigma = 272.6 +/- 376.8 MPa, m = 6.2 +/- 11.3, sigma0 = 294.0 +/- 394.1 MPa) and densely sintered alumina (sigma = 441.8 +/- 541.6 MPa, m = 11.9 +/- 19.0, sigma0 = 454.2 +/- 565.2 MPa). No statistically significant difference was found (P = 0.254) in glass infiltrated materials (sigma = 376.9 +/- 405.5 MPa, m = 7.5 +/- 11.5, sigma0 = 393.7 +/- 427.0 MPa). No statistically significant difference was found (P = 0.160) in densely sintered zirconia (sigma = 1,060.8 +/- 1,227.8 MPa, m = 5.8 +/- 7.4, sigma0 = 1,002.4 +/- 1,171.0 MPa). Not all the materials tested fulfilled the requirements for the clinical indications recommended by the manufacturer.

  5. "Ultra"-Fast Fracture Strength of Advanced Structural Ceramic Materials Studied at Elevated Temperatures

    Science.gov (United States)

    Choi, Sung R.; Gyekenyesi, John P.

    1999-01-01

    The accurate determination of inert strength is important in reliable life prediction of structural ceramic components. At ambient temperature, the inert strength of a brittle material is typically regarded as free of the effects of slow crack growth due to stress corrosion. Therefore, the inert strength can be determined either by eliminating active species, especially moisture, with an appropriate inert medium, or by using a very high test rate. However, at elevated temperatures, the concept or definition of the inert strength of brittle ceramic materials is not clear, since temperature itself is a degrading environment, resulting in strength degradation through slow crack growth and/or creep. Since the mechanism to control strength is rate-dependent viscous flow, the only conceivable way to determine the inert strength at elevated temperatures is to utilize a very fast test rate that either minimizes the time for or eliminates slow crack growth. Few experimental studies have measured the elevated-temperature, inert (or "ultra"-fast fracture) strength of advanced ceramics. At the NASA Lewis Research Center, an experimental study was initiated to better understand the "ultra"-fast fracture strength behavior of advanced ceramics at elevated temperatures. Fourteen advanced ceramics - one alumina, eleven silicon nitrides, and two silicon carbides - have been tested using constant stress-rate (dynamic fatigue) testing in flexure with a series of stress rates including the "ultra"-fast stress rate of 33 000 MPa/sec with digitally controlled test frames. The results for these 14 advanced ceramics indicate that, notwithstanding possible changes in flaw populations as well as flaw configurations because of elevated temperatures, the strength at 33 000 MPa/sec approached the room-temperature strength or reached a higher value than that determined at the conventional test rate of 30 MPa/sec. On the basis of the experimental data, it can be stated that the elevated

  6. Effect of Different Ceramic Crown Preparations on Tooth Structure Loss: An In Vitro Study

    Science.gov (United States)

    Ebrahimpour, Ashkan

    Objective: To quantify and compare the amount of tooth-structure reduction following the full-coverage preparations for crown materials of porcelain-fused-to-metal, lithium disilicate glass-ceramic and yttria-stabilized tetragonal zirconia polycrystalline for three tooth morphologies. Methods: Groups of resin teeth of different morphologies were individually weighed to high precision, then prepared following the preparation guidelines. The teeth were re-weighed after preparation and the amount of structural reduction was calculated. Statistical analyses were performed to find out if there was a significant difference among the groups. Results: Amount of tooth reduction for zirconia crown preparations was the lowest and statistically different compared with the other two materials. No statistical significance was found between the amount of reduction for porcelain-fused-to-metal and lithium disilicate glass-ceramic crowns. Conclusion: Within the limitations of this study, more tooth structure can be saved when utilizing zirconia full-coverage restorations compared with lithium disilicate glass-ceramic and porcelain-fused-to-metal crowns in maxillary central incisors, first premolars and first molars.

  7. Effects of pressure and temperature on pore structure of ceramic synthesized from rice husk: A small angle neutron scattering investigation

    International Nuclear Information System (INIS)

    Raut Dessai, R.; Desa, J.A.E.; Sen, D.; Mazumder, S.

    2013-01-01

    Highlights: ► A porous ceramic has been prepared from silica obtained from rice husk. ► The ceramic has a hierarchical pore structure from micrometric to nano-metric. ► Small Angle Neutron Scattering data indicate nano-pore connectivity to micro-pores. ► Pore morphology can be tuned by compaction pressure and sintering temperature. -- Abstract: Ceramic powder has been synthesized from rice husk as the source of silica. In order to probe the evolution of its hierarchical mesoscopic and microscopic porous structure, the ceramic powder was compacted at different pressures and was sintered at different temperatures. A glassy ceramic to crystalline transition under thermal treatment (up to 1000 °C) was revealed by X-ray diffraction. Existence of pores in two widely separated length scales was indicated by small angle neutron scattering with the smaller ones having mass fractal arrangement. Although no significant change in small pore structure under thermal effect was indicated, a significant modification of the same has been revealed by small angle neutron scattering at different compaction pressures. Connectivity between the pores was ascertained from scattering experiments on the ceramic compact impregnated with heavy water. Scanning electron microscopy shows the microstructure to undergo appreciable coalescence of micrometric ceramic particles for sintering temperature and pressure changes

  8. Fracture Resistance of Lithium Disilicate Ceramics Bonded to Enamel or Dentin Using Different Resin Cement Types and Film Thicknesses.

    Science.gov (United States)

    Rojpaibool, Thitithorn; Leevailoj, Chalermpol

    2017-02-01

    To investigate the influence of cement film thickness, cement type, and substrate (enamel or dentin) on ceramic fracture resistance. One hundred extracted human third molars were polished to obtain 50 enamel and 50 dentin specimens. The specimens were cemented to 1-mm-thick lithium disilicate ceramic plates with different cement film thicknesses (100 and 300 μm) using metal strips as spacers. The cements used were etch-and-rinse (RelyX Ultimate) and self-adhesive (RelyX U200) resin cements. Compressive load was applied on the ceramic plates using a universal testing machine, and fracture loads were recorded in Newtons (N). Statistical analysis was performed by multiple regression (p resin cement. Bonding to dentin resulted in lower fracture loads than bonding to enamel. Reduced resin film thickness could reduce lithium disilicate restoration fracture. Etch-and-rinse resin cements are recommended for cementing on either enamel or dentin, compared with self-adhesive resin cement, for improved fracture resistance. © 2015 by the American College of Prosthodontists.

  9. Structural Evolution of the R-T Phase Boundary in KNN-Based Ceramics

    KAUST Repository

    Lv, Xiang

    2017-10-04

    Although a rhombohedral-tetragonal (R-T) phase boundary is known to substantially enhance the piezoelectric properties of potassium-sodium niobate ceramics, the structural evolution of the R-T phase boundary itself is still unclear. In this work, the structural evolution of R-T phase boundary from -150 °C to 200 °C is investigated in (0.99-x)K0.5Na0.5Nb1-ySbyO3-0.01CaSnO3-xBi0.5K0.5HfO3 (where x=0~0.05 with y=0.035, and y=0~0.07 with x=0.03) ceramics. Through temperature-dependent powder X-ray diffraction (XRD) patterns and Raman spectra, the structural evolution was determined to be Rhombohedral (R, <-125 °C) → Rhombohedral+Orthorhombic (R+O, -125 °C to 0 °C) → Rhombohedral+Tetragonal (R+T, 0 °C to 150 °C) → dominating Tetragonal (T, 200 °C to Curie temperature (TC)) → Cubic (C, >TC). In addition, the enhanced electrical properties (e.g., a direct piezoelectric coefficient (d33) of ~450±5 pC/N, a conversion piezoelectric coefficient (d33*) of ~580±5 pm/V, an electromechanical coupling factor (kp) of ~0.50±0.02, and TC~250 °C), fatigue-free behavior, and good thermal stability were exhibited by the ceramics possessing the R-T phase boundary. This work improves understanding of the physical mechanism behind the R-T phase boundary in KNN-based ceramics and is an important step towards their adoption in practical applications. This article is protected by copyright. All rights reserved.

  10. Fracture resistance of three ceramic inlay-retained fixed partial denture designs. An in vitro comparative study.

    Science.gov (United States)

    Mohsen, Cherif A

    2010-10-01

    The fracture resistance of ceramic inlay-retained fixed partial dentures (CIRFPDs) was studied. Thirty CIRFPDs were constructed using ice zircon milled ceramic material. Specimens were divided into three groups, 10 specimens each, according to the abutment preparation: inlay-shaped (occluso-proximal inlay + proximal box), tub-shaped (occluso-proximal inlay), and proximal box-shaped preparations. Each group was then subdivided into two subgroups of five specimens each, according to the span of the edentulous area representing a missing premolar or molar. All specimens were subjected to a fracture resistance test. CIRFPDs with inlay-shaped retainers showed the highest fracture resistance values for missing premolars and molars. CIRFPDs with box-shaped retainers showed lower fracture resistance values. Statistical analysis revealed a significant difference between the three tested CIRFPD designs. There was a statistically significant difference between CIRFPDs constructed for the replacement of molars and those constructed for the replacement of premolars. The CIRFPD constructed for the replacement of molars gave lower fracture resistance values with the three tested designs. All the fracture resistance values obtained in this study were superior to the assumed maximum mastication forces. Failure mode was delamination and chipping of the veneering material. There was a statistically significant difference between the three designs of CIRPFDs tested. There was a statistically significant difference between CIRFPDs constructed for the replacement of molars than those constructed for the replacement of premolars. The CIRFPDs constructed for the replacement of molars gave lower fracture resistance values with the three tested designs. All fracture resistance values obtained in this study were superior to the assumed maximum mastication forces. © 2010 by The American College of Prosthodontists.

  11. Fiscal 1997 achievement report. Research and development of synergy ceramics; 1997 nendo synergy ceramics no kenkyu kaihatsu seika hokokusho

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-03-01

    Research and development is conducted on two subjects, that is, 1) hyper organized structure control technology and 2) structural element control technology. In addition, joint research and development is conducted on the creation of new materials by hyper organized structure controlling, hyper organized structure controlling for ceramics by a structurization reaction process, designing of precursors to ceramics, and the hyper organized structure control for ceramics by nanostructure process control. The joint research and development endeavors further deal with re-entrusted projects which involve researches on sintered structure control by powdery particulate structure control; dynamic process of synergy ceramics; oxynitride liquids, glasses, and glass-ceramics; and multifunctional ceramic laminates for engineering applications. Under subject 1), researches are made on the development of precursors into ceramics by utilizing chemical reactions of organic metal compounds, and analyses are conducted into the effects, exerted by the molecular structures of precursors and the conditions of a reaction for their development into ceramics, on the microstructures and various properties of the ceramics to be composed. Under subject 2), high strength, great hardness, and high resistance to wear are realized by allowing the precipitation of nano-particulates in crystals of a fine and very compact sintered body of alumina. (NEDO)

  12. Synthesis, structure, thermal, transport and magnetic properties of VN ceramics

    Czech Academy of Sciences Publication Activity Database

    Huber, Š.; Jankovský, O.; Sedmidubský, D.; Luxa, J.; Klimová, K.; Hejtmánek, Jiří; Sofer, Z.

    2016-01-01

    Roč. 42, č. 16 (2016), s. 18779-18784 ISSN 0272-8842 R&D Projects: GA ČR GA13-20507S Institutional support: RVO:68378271 Keywords : vanadium mononitride * phase transition * electronic structure * heat capacity * transport properties Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.986, year: 2016

  13. Theoretical Research on Thermal Shock Resistance of Ultra-High Temperature Ceramics Focusing on the Adjustment of Stress Reduction Factor

    Directory of Open Access Journals (Sweden)

    Daining Fang

    2013-02-01

    Full Text Available The thermal shock resistance of ceramics depends on not only the mechanical and thermal properties of materials, but also the external constraint and thermal condition. So, in order to study the actual situation in its service process, a temperature-dependent thermal shock resistance model for ultra-high temperature ceramics considering the effects of the thermal environment and external constraint was established based on the existing theory. The present work mainly focused on the adjustment of the stress reduction factor according to different thermal shock situations. The influences of external constraint on both critical rupture temperature difference and the second thermal shock resistance parameter in either case of rapid heating or cooling conditions had been studied based on this model. The results show the necessity of adjustment of the stress reduction factor in different thermal shock situations and the limitations of the applicable range of the second thermal shock resistance parameter. Furthermore, the model was validated by the finite element method.

  14. CARES/LIFE Ceramics Analysis and Reliability Evaluation of Structures Life Prediction Program

    Science.gov (United States)

    Nemeth, Noel N.; Powers, Lynn M.; Janosik, Lesley A.; Gyekenyesi, John P.

    2003-01-01

    This manual describes the Ceramics Analysis and Reliability Evaluation of Structures Life Prediction (CARES/LIFE) computer program. The program calculates the time-dependent reliability of monolithic ceramic components subjected to thermomechanical and/or proof test loading. CARES/LIFE is an extension of the CARES (Ceramic Analysis and Reliability Evaluation of Structures) computer program. The program uses results from MSC/NASTRAN, ABAQUS, and ANSYS finite element analysis programs to evaluate component reliability due to inherent surface and/or volume type flaws. CARES/LIFE accounts for the phenomenon of subcritical crack growth (SCG) by utilizing the power law, Paris law, or Walker law. The two-parameter Weibull cumulative distribution function is used to characterize the variation in component strength. The effects of multiaxial stresses are modeled by using either the principle of independent action (PIA), the Weibull normal stress averaging method (NSA), or the Batdorf theory. Inert strength and fatigue parameters are estimated from rupture strength data of naturally flawed specimens loaded in static, dynamic, or cyclic fatigue. The probabilistic time-dependent theories used in CARES/LIFE, along with the input and output for CARES/LIFE, are described. Example problems to demonstrate various features of the program are also included.

  15. Frictional resistances of metal-lined ceramic brackets versus conventional stainless steel brackets and development of 3-D friction maps.

    Science.gov (United States)

    Kusy, R P; Whitley, J Q

    2001-10-01

    The frictional resistances of 2 metal-lined ceramic brackets (Luxi and Clarity) were compared with 2 conventional stainless steel brackets (Mini-Taurus and Mini-Twin) in vitro. In method 1, we varied the second-order angulation from 0 degrees to 12 degrees while maintaining the normal or ligature force constant at 0.3 kg; in method 2, we varied the ligature force from 0.1 kg to 0.9 kg while maintaining the angulation at theta = 0 degrees or theta = 11 degrees. The hardware simulated a 3-bracket system in which the interbracket distances were always 18 mm. All couples were evaluated at 34 degrees C using the same size stainless steel archwire (19 x 26 mil) and ligature wire (10 mil). In the passive region, the static and kinetic frictional forces and coefficients of friction were key parameters; in the active region, the static and kinetic binding forces and coefficients of binding were critical parameters. From outcomes of methods 1 and 2, the 4 aforementioned parameters, and a knowledge of the critical contact angle for binding, 3-dimensional friction maps were constructed in the dry and wet states from which the frictional resistances could be determined at any ligature force or second-order angulation. Those 3-dimensional maps show that metal-lined ceramic brackets can function comparably to conventional stainless steel brackets and that 18-kt gold inserts appear superior to stainless steel inserts. As the morphologies of metal inserts are improved, these metal-lined ceramic brackets will provide not only good esthetics among ceramic brackets but also minimal friction among conventionally ligated brackets.

  16. Diamond-Structure Photonic Crystals Composed of Ceramic Spheres in Resin and Their Microwave Properties

    Science.gov (United States)

    Nakagawa, Takuji; Kageyama, Keisuke; Takagi, Hiroshi; Sakabe, Yukio; Kirihara, Soshu; Miyamoto, Yoshinari

    2007-10-01

    Three-dimensional (3D) photonic crystals with a diamond structure composed of TiO2 ceramic spheres in a resin matrix were fabricated by stereolithography. The lattice constant was 12 mm. The diameter of the spheres was about 5 mm. These photonic crystals composed of ceramic spheres showed four complete photonic band gaps at around 5.7 GHz between the 2nd and 3rd bands, 7.8 GHz between the 8th and 9th bands, 10.4 GHz between the 24th and 25th bands, and 13.1 GHz between the 54th and 55th bands. The propagation characteristics of microwaves propagating through the photonic crystals agreed well with the calculated results using the plane-wave expansion method.

  17. Structure, Ferroelectric and Photoluminescence Properties of Eu-Doped CaBi4Ti4O15 Multifunctional Ceramics

    Science.gov (United States)

    Wu, Xiaochun; Xiao, Ping; Guo, Yongquan; Zheng, Qiaoji; Lin, Dunmin

    2015-10-01

    Lead-free multifunctional ceramics of CaBi4- x Eu x Ti4O15 were prepared by a traditional solid state method, and the effects of Eu doping on structure, ferroelectric, piezoelectric and photoluminescence properties of the ceramics were investigated. All the ceramics possessed typical bismuth layer structure with m = 4, belonging to orthorhombic symmetry, and no secondary phase was detected. The plate-like grains were observed in all the ceramics, and the grain growth was slightly inhibited after the addition of Eu. Saturated polarization hysteresis loops were observed for all the ceramics, and the remanent polarization P r decreased with Eu doping. The Eu-doped ceramics had a sharp excitation band centered at 465 nm due to the f-f transition from the 7F0 ground state to the 5D2 excited state of Eu3+. Under the excitation by 465 nm light, the main emission peaks located at 595 nm and 616 nm were obtained, which corresponds to the transition of 5D0-7F1, 5D0-7F2 levels in Eu3+, respectively. Our study shows that CaBi4Ti4O15 ceramics may be a promising multifunctional material for potential applications in optical-electro integration devices.

  18. Structure and properties of sodium bismuth titanate ferroelectric ceramics

    Science.gov (United States)

    Aksel, Elena

    Piezoelectric materials are commonly used in sensor and actuator technologies due to their unique ability to couple electrical and mechanical displacements. Applications of piezoelectric materials range from diesel engine fuel injectors, sonar, ultrasound, and nanopositioners in scanning microscopes. Changing environmental regulations and policies have led to a recent surge in the research of lead-free piezoelectric materials. One such system currently under investigation is sodium bismuth titanate (Na0.5Bi0.5 TiO3) or NBT. It has recently been investigated with the addition of chemical modifiers as well as part of various solid solutions with other compounds. However, research into the structure and properties of NBT is still in its infancy. The aim of this dissertation was to develop a comprehensive understanding of the crystal structure and property relationships in NBT. First, the formation of the NBT phase during solid state processing was examined using in situ X-ray diffraction. It was determined that NBT forms through a particle conversion mechanism of the Bi2O 3 particle. The average and local room temperature structure of calcined and sintered NBT were examined using both high resolution synchrotron X-ray diffraction and neutron diffraction techniques. It was determined that the room temperature average structure of this material is best modeled using the monoclinic Cc space group rather than the previously accepted rhombohedral R3c space group. A combined high resolution XRD and neutron diffraction Rietveld refinement provided refined lattice parameters, atomic positions, and displacement parameters. The departure of the local structure of NBT from the average structure was examined through the Pair Distribution Function analysis. It was determined that Na+ and Bi3+, which share the A-site, have differing bonding environments with their surrounding O2- ions. In order to understand the origin of the piezoelectric depolarization behavior of NBT, crystal

  19. 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 ...

  20. Structural analysis and thermal behavior of diopside-fluorapatite-wollastonite-based glasses and glass-ceramics.

    Science.gov (United States)

    Kansal, Ishu; Tulyaganov, Dilshat U; Goel, Ashutosh; Pascual, Maria J; Ferreira, José M F

    2010-11-01

    Glass-ceramics in the diopside (CaMgSi2O6)-fluorapatite (Ca5(PO4)3F)-wollastonite (CaSiO3) system are potential candidates for restorative dental and bone implant materials. The present study describes the influence of varying SiO2/CaO and CaF2/P2O5 molar ratio on the structure and thermal behavior of glass compositions in the CaO-MgO-SiO2-P2O5-Na2O-CaF2 system. The structural features and properties of the glasses were investigated by nuclear magnetic resonance (NMR), infrared spectroscopy, density measurements and dilatometry. Sintering and crystallization behavior of the glass powders were studied by hot-stage microscopy and differential thermal analysis, respectively. The microstructure and crystalline phase assemblage in the sintered glass powder compacts were studied under non-isothermal heating conditions at 825 °C. X-ray diffraction studies combined with the Rietveld-reference intensity ratio (R.I.R) method were employed to quantify the amount of amorphous and crystalline phases in the glass-ceramics, while scanning electron microscopy was used to shed some light on the microstructure of resultant glass-ceramics. An increase in CaO/SiO2 ratio degraded the sinterability of the glass powder compacts, resulting in the formation of akermanite as the major crystalline phase. On the other hand, an increase in P2O5/CaF2 ratio improved the sintering behavior of the glass-ceramics, while varying the amount of crystalline phases, i.e. diopside, fluorapatite and wollastonite. Copyright © 2010. Published by Elsevier Ltd.

  1. Open pore structure analysis of lithium bearing ceramics

    International Nuclear Information System (INIS)

    Elbel, H.

    1988-01-01

    The analysis of the open pore structure includes mercury porosimetry, helium stereopycnometry, gas permeability and specific surface area measurements. These methods were used in the analysis of different types of Li 2 SiO 3 and Li j SiO 4 specimens whose behaviour is tested under operation conditions in various irradiation experiments. Mercury porosimetry yielded density of the specimens, size distribution of the channels and amount of the open porosity. The correlation between mercury pressure and channel diameter was approximated by the Washburn equation. Density determinations by means of helium stereopycnometry demonstrated the existence of open pore volume below the mercury porosimetry detection. Additional information about the structure of open porosity was obtained by gas permeability measurements evaluated using the Carman relation, which is a generalization of the Hagen-Poiseuille law. This approach correlates structure parameters of the open porosity with permeability coefficients. The specific surface area was determined by applying the BET theory to volumetric nitrogen gas adsorption. (orig.)

  2. Study on Coloration Mechanism of Chinese Ancient Ceramics by X-ray Absorption Near-edge Structure

    International Nuclear Information System (INIS)

    Peng, Y H; Xie, Z; He, J F; Liu, Q H; Pan, Z Y; Cheng, W R; Wei, S Q

    2013-01-01

    The Fe K-edge X-ray absorption near-edge structure (XANES) spectra of a series of ceramic shards were measured by fluorescence mode to reveal the color-generating techniques of Chinese porcelain. The analysis disclosed relationships among the chemical form of the iron, the firing conditions and the colors of the ceramics. The results indicate that the coloration for different ceramics depend on the valence states of iron as the main color element in glaze and the proportion of Fe 2+ and Fe 3+ was attributed to the baking technology. The findings provide important information for archaeologist on the coloration researches.

  3. Thermal shock resistance of ceramic fibre composites characterized by non-destructive methods

    Directory of Open Access Journals (Sweden)

    M. Dimitrijević

    2008-12-01

    Full Text Available Alumina based ceramic fibres and alumina based ceramic were used to produce composite material. Behaviour of composite ceramics after thermal shock treatments was investigated. Thermal shock of the samples was evaluated using water quench test. Surface deterioration level of samples was monitored by image analysis before and after a number of quenching cycles. Ultrasonic measurements were done on samples after quench tests. Dynamic Young modulus of elasticity and strength degradation were calculated using measured values of ultrasonic velocities. Strengths deterioration was calculated using the non-destructive measurements and correlated to degradation of surface area and number of quenches. The addition of small amount of ceramic fibres improves the strengths and diminishes the loss of mechanical properties of samples during thermal shock experiments.

  4. On electronic structure of polymer-derived amorphous silicon carbide ceramics

    Science.gov (United States)

    Wang, Kewei; Li, Xuqin; Ma, Baisheng; Wang, Yiguang; Zhang, Ligong; An, Linan

    2014-06-01

    The electronic structure of polymer-derived amorphous silicon carbide ceramics was studied by combining measurements of temperature-dependent conductivity and optical absorption. By comparing the experimental results to theoretical models, electronic structure was constructed for a carbon-rich amorphous silicon carbide, which revealed several unique features, such as deep defect energy level, wide band-tail band, and overlap between the band-tail band and defect level. These unique features were discussed in terms of the microstructure of the material and used to explain the electric behavior.

  5. Structure, chemistry and adhesion of ion-plated metal/ceramic interfaces

    International Nuclear Information System (INIS)

    Rigsbee, J.M.; Scott, P.A.; Knipe, R.K.; Ju, C.P.

    1985-01-01

    Cu and Ti elemental films have been deposited onto cordierite-type ceramic substrates by ion-plating. This paper presents the initial results of a research program which addresses how the structure and chemistry of the metal/ceramic interface is modified as a function of the deposition process parameters and the substrate surface roughness. While evaporated Cu films on polished substrates had essentially zero adhesion, films deposited with an applied substrate bias showed increasing adhesive strength with increasing bias. Microchemical analysis indicated that this enhanced adhesion is directly correlated with the development of a chemically graded interface region. The adhesive strength of the ion plated Cu films was also found to be improved with increasing substrate smoothness. Although the generally superior adhesion of Ti was evident for films either evaporated or deposited with low bias voltage/current, this adhesion actually decreased for films deposited with high bias voltage/current. This effect results from the formation of a compound at the Ti/ceramic interface region. Results indicate that the thickness of this apparently brittle compound plays a critical role in film adhesion. (author)

  6. Fracture resistance of computer-aided design and computer-aided manufacturing ceramic crowns cemented on solid abutments.

    Science.gov (United States)

    Stona, Deborah; Burnett, Luiz Henrique; Mota, Eduardo Gonçalves; Spohr, Ana Maria

    2015-07-01

    Because no information was found in the dental literature regarding the fracture resistance of all-ceramic crowns using CEREC (Sirona) computer-aided design and computer-aided manufacturing (CAD-CAM) system on solid abutments, the authors conducted a study. Sixty synOcta (Straumann) implant replicas and regular neck solid abutments were embedded in acrylic resin and randomly assigned (n = 20 per group). Three types of ceramics were used: feldspathic, CEREC VITABLOCS Mark II (VITA); leucite, IPS Empress CAD (Ivoclar Vivadent); and lithium disilicate, IPS e.max CAD (Ivoclar Vivadent). The crowns were fabricated by the CEREC CAD-CAM system. After receiving glaze, the crowns were cemented with RelyX U200 (3M ESPE) resin cement under load of 1 kilogram. For each ceramic, one-half of the specimens were subjected to the fracture resistance testing in a universal testing machine with a crosshead speed of 1 millimeter per minute, and the other half were subjected to the fractured resistance testing after 1,000,000 cyclic fatigue loading at 100 newtons. According to a 2-way analysis of variance, the interaction between the material and mechanical cycling was significant (P = .0001). According to a Tukey test (α = .05), the fracture resistance findings with or without cyclic fatigue loading were as follows, respectively: CEREC VITABLOCKS Mark II (405 N/454 N) was statistically lower than IPS Empress CAD (1169 N/1240 N) and IPS e.max CAD (1378 N/1025 N) (P  .05). According to a t test, there was no statistical difference in the fracture resistance with and without cyclic fatigue loading for CEREC VITABLOCS Mark II and IPS Empress CAD (P > .05). For IPS e.max CAD, the fracture resistance without cyclic fatigue loading was statistically superior to that obtained with cyclic fatigue loading (P crowns cemented on solid abutments showed sufficient resistance to withstand normal chewing forces. Copyright © 2015 American Dental Association. Published by Elsevier Inc. All

  7. The Use of Heat-Resistant Concrete Made with Ceramic Sanitary Ware Waste for a Thermal Energy Storage

    Directory of Open Access Journals (Sweden)

    Paweł Ogrodnik

    2017-12-01

    Full Text Available The paper presents the results obtained in the course of a study on the concrete made of aggregate obtained from wastes of sanitary ceramics. Previous examinations proved high in strength and durability of concrete of this type, and it showed a resistance to high temperatures. The material was classified as a fireproof concrete. While searching for the optimal applications of such concrete, a series of examinations and analyses on its thermal energy storage (TES properties were performed. This paper describes the two-stage experiment on the thermal behavior of the concrete made with sanitary ceramic wastes during cooling processes in comparison to different building materials subjected to the same thermal conditions. On the basis of the thermal, infrared analysis, and suitable calculations, the thermal power and the ability of the composite to store thermal energy was estimated. Finally, it was stated that the concrete made of sanitary ceramic waste aggregate and alumina cement can be recommended as a heat-accumulating material, and in combination with high durability can be used, e.g., for the construction of fireplace bodies.

  8. Fracture resistance of prepared premolars restored with bonded new lab composite and all-ceramic inlay/onlay restorations: Laboratory study.

    Science.gov (United States)

    Wafaie, Ramy Ahmed; Ibrahim Ali, Ashraf; Mahmoud, Salah Hasab

    2018-01-25

    To assess the influence of new light curing lab composite, lithium-disilicate glass-ceramic and yttrium-stabilized zirconia-based ceramic on the fracture resistance of maxillary premolars with class II inlay and onlay preparations. Seventy sound maxillary premolars were divided randomly into seven main groups. The first group was left intact (control group). The remaining six groups were prepared with inlay and onlay cavities and restored with lab composite (SR Nexco), lithium-disilicate glass-ceramic (IPS e.max Press) and yttrium-stabilized zirconia-based ceramic (ICE Zirkon). The restorations were cemented with luting resin composite (Variolink N). All specimens were thermocycled 5000 cycles between 5°C ± 2°C and 55°C ± 2°C and were then cyclic loaded for 500 000 cycles. The specimens were subjected to a compressive load in a universal testing machine using a metal sphere until fracture occurred. The results were analyzed by 2-way ANOVA and Tukey HSD post hoc tests. The level of significance was set at P inlays and onlays (P > .05). However, statistically significant differences were found among the means of control group and the groups restored with lab composite inlays, lab composite onlays, pressable glass ceramic inlays and pressable glass ceramic onlays (P inlay and onlay restorations is inferior to the intact teeth when lab composite is used. Conversely, when a ceramic material being used, the prepared teeth for inlay and onlay restorations showed a comparable strength to the intact teeth especially zirconia ceramic. Premolar teeth restored with zirconia ceramic inlays and onlays exhibited fracture resistance comparable to intact teeth. © 2018 Wiley Periodicals, Inc.

  9. The effect of silane applied to glass ceramics on surface structure and bonding strength at different temperatures.

    Science.gov (United States)

    Yavuz, Tevfik; Eraslan, Oguz

    2016-04-01

    To evaluate the effect of various surface treatments on the surface structure and shear bond strength (SBS) of different ceramics. 288 specimens (lithium-disilicate, leucite-reinforced, and glass infiltrated zirconia) were first divided into two groups according to the resin cement used, and were later divided into four groups according to the given surface treatments: G1 (hydrofluoric acid (HF)+silane), G2 (silane alone-no heat-treatment), G3 (silane alone-then dried with 60℃ heat-treatment), and G4 (silane alone-then dried with 100℃ heat-treatment). Two different adhesive luting systems were applied onto the ceramic discs in all groups. SBS (in MPa) was calculated from the failure load per bonded area (in N/mm(2)). Subsequently, one specimen from each group was prepared for SEM evaluation of the separated-resin-ceramic interface. SBS values of G1 were significantly higher than those of the other groups in the lithium disilicate ceramic and leucite reinforced ceramic, and the SBS values of G4 and G1 were significantly higher than those of G2 and G3 in glass infiltrated zirconia. The three-way ANOVA revealed that the SBS values were significantly affected by the type of resin cement (P<.001). FIN ceramics had the highest rate of cohesive failure on the ceramic surfaces than other ceramic groups. AFM images showed that the surface treatment groups exhibited similar topographies, except the group treated with HF. The heat treatment was not sufficient to achieve high SBS values as compared with HF acid etching. The surface topography of ceramics was affected by surface treatments.

  10. Study of the structure of ferroelectric domain walls in barium titanate ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Normand, L.; Thorel, A. [Centre des Materiaux, Evry cedex (France) ; Kilaas, R. [Lawrence Berkeley Lab., CA (United States); Montardi, Y. [Rhone-Poulenc, CRA, Aubervilliers (France)

    1995-02-01

    Structure of 90{degree} ferroelectric domain boundaries in barium titanate ceramics has been studied by means of Transmission Electron Microscopy and High Resolution TEM. Tilts of specific fringes across domain walls are measured on HREM images and Selected Area Diffraction Patterns. They are in a good agreement with the twin model admitted for these domain boundaries. A computerized method has been developed to give access to quantitative information about atomic displacements across these ferroelectric domain walls. The so calculated displacement field is then compared with Landau-Ginzburg based theoretical predictions.

  11. 1/f Noise in Ceramic Superconductors and Granular Resistors

    OpenAIRE

    Takagi, Keiji; Mizunami, Toru; Okayama, Hideyuki; Shiyuan, Yang

    1990-01-01

    The authors have measured the current noise in some components of granular structure. The samples are ceramic superconductors, carbon-black graft-polymer resistors, and positive temperature coefficient(PTe) ceramics. All noise spectra are of the 1/! type. The temperature dependence of the noise level is measured and compared with the temperature dependence of the resistance, It is shown that in these components the temperature coefficient of the resistance is related to the noise level as pre...

  12. Structure effect on wear resistance of alloys

    International Nuclear Information System (INIS)

    Stepina, A.I.; Sidorova, L.I.; Tolstenko, E.V.

    1982-01-01

    The dependence of wear resistance on hardness of steels with different microstructure is studied under conditions of gas-abrasion wear of surface layers. It is found out that at the same hardness the wear resistance of α-alloys is higher than that of γ-alloys in spite of considerable surface hardening of austenitic alloys. Fracture of surface in the process of abrasive wear occurs after achievement of definite values of microhardness and the width of a diffraction line for each structural class of alloys [ru

  13. Mechanical Properties and Plasma Erosion Resistance of ZrO{sub 2p}(3Y)/BN-SiO{sub 2} Ceramic Composites under Different Sintering Temperature

    Energy Technology Data Exchange (ETDEWEB)

    Zhou Yu; Duan Xiaoming; Jia Dechang; Yang Zhihua; Meng Qingchang; Yu Yang [Institute for Advanced Ceramics, Harbin Institute of Technology, Harbin, 150001 (China); Yu Daren; Ding Yongjie, E-mail: dxmhit@126.com [School of Energy Science and Technology, Harbin Institute of Technology, Harbin, 150001 (China)

    2011-10-29

    ZrO{sub 2p}(3Y)/BN-SiO{sub 2} ceramic composites were hot pressed under different sintering temperature. The ceramic composites were composed by BN, m-ZrO{sub 2}, t-ZrO{sub 2} and SiO{sub 2}. The relative density, bending strength, elastic modulus and fracture toughness increase with the sintering temperature increasing, the maximum value of which at the sintering temperature of 1800 deg. C are 97.5%, 229.9MPa, 60.8GPa and 3.55MPam{sup 1/2}, respectively. The erosion resistance ability of ZrO{sub 2p}(3Y)/BN-SiO{sub 2} ceramic composites rise gradually with the sintering temperature increasing, and the erosion rate of the ceramic composite sintered at 1800 deg. C is 8.03x10{sup -3}mm/h.

  14. Modification of Structure and Tribological Properties of the Surface Layer of Metal-Ceramic Composite under Electron Irradiation in the Plasmas of Inert Gases

    Science.gov (United States)

    Ovcharenko, V. E.; Ivanov, K. V.; Mohovikov, A. A.; Yu, B.; Xu, Yu; Zhong, L.

    2018-01-01

    Metal-ceramic composites are the main materials for high-load parts in tribomechanical systems. Modern approaches to extend the operation life of tribomechanical systems are based on increasing the strength and tribological properties of the surface layer having 100 to 200 microns in depth. The essential improvement of the properties occurs when high dispersed structure is formed in the surface layer using high-energy processing. As a result of the dispersed structure formation the more uniform distribution of elastic stresses takes place under mechanical or thermal action, the energy of stress concentrators emergence significantly increases and the probability of internal defects formation reduces. The promising method to form the dispersed structure in the surface layer is pulse electron irradiation in the plasmas of inert gases combining electron irradiation and ion bombardment in one process. The present work reports upon the effect of pulse electron irradiation in plasmas of different inert gases with different atomic mass and ionization energy on the structure and tribological properties of the surface layer of TiC/(Ni-Cr) metal-ceramic composite with the volume ratio of the component being 50:50. It is experimentally shown that high-dispersed heterophase structure with a fraction of nanosized particles is formed during the irradiation. Electron microscopy study reveals that refining of the initial coarse TiC particles occurs via their dissolution in the molten metal binder followed by the precipitation of secondary fine particles in the interparticle layers of the binder. The depth of modified layer and the fraction of nanosized particles increase when the atomic number of the plasma gas increases and ionization energy decreases. The wear resistance of metal-ceramic composite improves in accordance to the formation of nanocrystalline structure in the surface layer.

  15. Formation of Green compact structure of low-temperature ceramics with taking into account the thermal degradation of the binder

    Science.gov (United States)

    Tovpinets, A. O.; Leytsin, V. N.; Dmitrieva, M. A.; Ivonin, I. V.; Ponomarev, S. V.

    2017-12-01

    The solution of the tasks in the field of creating and processing materials for additive technologies requires the development of a single theory of materials for various applications and processes. A separate class of materials that are promising for use in additive technologies includes materials whose consolidation is ensured by the presence of low-melting components in the initial mixture which form a matrix at a temperature not exceeding the melting point, recrystallization or destruction of any of the responsible refractory components of the initial dispersion. The study of the contribution of the binder thermal destruction to the structure and phase composition of the initial compact of the future composite is essential for the development of modern technologies for the synthesis of low-temperature ceramics. This paper investigates the effect of the thermal destruction of a binder on the formation of a green compact of low-temperature ceramics and the structural-mechanical characteristics of sintered ceramics. The approach proposed in Ref. [1] for evaluating the structure and physical characteristics of sintered low-temperature ceramics is improved to clarify the structure of green compacts obtained after thermal destruction of the polymer binder, with taking into account the pores formed and the infusible residue. The obtained results enable a more accurate prediction of thermal stresses in the matrix of sintered ceramics and serve as a basis for optimization.

  16. Crystal structure and ferroelectric properties of Ca(Cu3−xMx)Ti4O12 (M = Fe and Ni) ceramics

    International Nuclear Information System (INIS)

    Moriyama, Tohru; Kan, Akinori; Ogawa, Hirotaka

    2013-01-01

    Highlights: ► M-substituted Ca(Cu 3−x M x )Ti 4 O 12 (CCMTO) ceramics, where M = Fe and Ni, were synthesized. ► The influence of M substitution for Cu on crystal structure and ferroelectric properties of CCMTO ceramics were investigated. ► Analysis of CCMTO ceramics revealed the single phase of CCMTO ceramics belongs to I23 non-centrosymmetric space group of I23. ► As a result, the P r and E c values of CCFTO ceramics at x = 0.05 were 1.8 μC/cm 2 and 40 kV/cm, respectively. -- Abstract: M-substituted Ca(Cu 3−x M x )Ti 4 O 12 (CCMTO) ceramics, where M = Fe and Ni, were synthesized and the influence of M substitutions for Cu on the crystal structure and ferroelectric properties of CCMTO ceramics were investigated in this study. From the variations in the lattice parameters of CCMTO ceramics, the solubility limit of Ni substitution for Cu in CaCu 3−x Ni x Ti 4 O 12 (CCNTO) ceramics was x = 0.2, whereas that of CaCu 3−x Fe x Ti 4 O 12 (CCFTO) ceramics was x = 0.05. The crystal structural analysis of CCMTO ceramics revealed that the single phase of CCMTO ceramics belongs to the I23 non-centrosymmetric space group of I23; as a result, the P r and E c values of CCFTO ceramics at x = 0.05 were 1.8 μC/cm 2 and 40 kV/cm, respectively. The ferroelectric behavior of CCMTO ceramics by the M substitutions for Cu may be related to the displacement of a Ti 4+ cation in the TiO 6 octahedra and tilting of the Ti–O–Ti angle because of the non-centrosymmetric space group

  17. Fracture resistance and failure modes of polymer infiltrated ceramic endocrown restorations with variations in margin design and occlusal thickness.

    Science.gov (United States)

    Taha, Doaa; Spintzyk, Sebastian; Schille, Christine; Sabet, Ahmed; Wahsh, Marwa; Salah, Tarek; Geis-Gerstorfer, Jürgen

    2017-12-11

    The purpose of this in vitro study was to assess the effect of varying the margin designs and the occlusal thicknesses on the fracture resistance and mode of failures of endodontically treated teeth restored with polymer infiltrated ceramic endocrown restorations. Root canal treated mandibular molars were divided into four groups (n=8) and were prepared to receive Computer-Aided Design/Computer-Aided Manufacturing (CAD/CAM) fabricated polymer infiltrated ceramic endocrowns (ENAMIC blocks). Group B2 represents teeth prepared with a butt joint design receiving endocrowns with 2mm occlusal thickness and the same for group B3.5 but with 3.5mm occlusal thickness. Group S2 represents teeth prepared with 1mm shoulder finish line receiving endocrowns with 2mm occlusal thickness and the same for group S3.5 but with 3.5mm occlusal thickness. After cementation and thermal aging, fracture resistance test was performed and failure modes were observed. Group S3.5 showed the highest mean fracture load value (1.27±0.31kN). Endocrowns with shoulder finish line had significantly higher mean fracture resistance values than endocrowns with butt margin (p<0.05). However, the results were not statistically significant regarding the restoration thickness. Evaluation of the fracture modes revealed no statistically significant difference between the modes of failure of tested groups. For the restoration of endodontically treated teeth, adding a short axial wall and shoulder finish line can increase the fracture resistance. However, further investigations, especially the fatigue behavior, are needed to ensure this effect applies with small increases of restoration thickness. Copyright © 2017 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

  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. Development and optimization of manufacture process for heat resistant fibre reinforced ceramic matrix composites

    Czech Academy of Sciences Publication Activity Database

    Glogar, Petr; Hron, P.; Burian, M.; Balík, Karel; Černý, Martin; Sucharda, Zbyněk; Vymazalová, Z.; Červencl, J.; Pivoňka, M.

    -, č. 14 (2005), 25-32 ISSN 1214-9691 R&D Projects: GA ČR(CZ) GA106/02/0177 Institutional research plan: CEZ:AV0Z30460519 Keywords : polysiloxane resin * pyrolysis * ceramic matrix composite Subject RIV: JI - Composite Materials

  20. A sputtered zirconia primer for improved thermal shock resistance of plasma sprayed ceramic turbine seals

    Science.gov (United States)

    Bill, R. C.; Sovey, J.; Allen, G. P.

    1981-01-01

    The development of plasma-sprayed yttria stabilized zirconia (YSZ) ceramic turbine blade tip seal components is discussed. The YSZ layers are quite thick (0.040 to 0.090 in.). The service potential of seal components with such thick ceramic layers is cyclic thermal shock limited. The most usual failure mode is ceramic layer delamination at or very near the interface between the plasma sprayed YSZ layer and the NiCrAlY bondcoat. Deposition of a thin RF sputtered YSZ primer to the bondcoat prior to deposition of the thick plasma sprayed YSZ layer was found to reduce laminar cracking in cyclic thermal shock testing. The cyclic thermal shock life of one ceramic seal design was increased by a factor of 5 to 6 when the sputtered YSZ primer was incorporated. A model based on thermal response of plasma sprayed YSZ particles impinging on the bondcoat surface with and without the sputtered YSZ primer provides a basis for understanding the function of the primer.

  1. The effect of silane applied to glass ceramics on surface structure and bonding strength at different temperatures

    Science.gov (United States)

    Eraslan, Oguz

    2016-01-01

    PURPOSE To evaluate the effect of various surface treatments on the surface structure and shear bond strength (SBS) of different ceramics. MATERIALS AND METHODS 288 specimens (lithium-disilicate, leucite-reinforced, and glass infiltrated zirconia) were first divided into two groups according to the resin cement used, and were later divided into four groups according to the given surface treatments: G1 (hydrofluoric acid (HF)+silane), G2 (silane alone-no heat-treatment), G3 (silane alone-then dried with 60℃ heat-treatment), and G4 (silane alone-then dried with 100℃ heat-treatment). Two different adhesive luting systems were applied onto the ceramic discs in all groups. SBS (in MPa) was calculated from the failure load per bonded area (in N/mm2). Subsequently, one specimen from each group was prepared for SEM evaluation of the separated-resin–ceramic interface. RESULTS SBS values of G1 were significantly higher than those of the other groups in the lithium disilicate ceramic and leucite reinforced ceramic, and the SBS values of G4 and G1 were significantly higher than those of G2 and G3 in glass infiltrated zirconia. The three-way ANOVA revealed that the SBS values were significantly affected by the type of resin cement (Pceramics had the highest rate of cohesive failure on the ceramic surfaces than other ceramic groups. AFM images showed that the surface treatment groups exhibited similar topographies, except the group treated with HF. CONCLUSION The heat treatment was not sufficient to achieve high SBS values as compared with HF acid etching. The surface topography of ceramics was affected by surface treatments. PMID:27141250

  2. Influence of heat treatment on bond strength and corrosion resistance of sol-gel derived bioglass-ceramic coatings on magnesium alloy.

    Science.gov (United States)

    Shen, Sibo; Cai, Shu; Xu, Guohua; Zhao, Huan; Niu, Shuxin; Zhang, Ruiyue

    2015-05-01

    In this study, bioglass-ceramic coatings were prepared on magnesium alloy substrates through sol-gel dip-coating route followed by heat treatment at the temperature range of 350-500°C. Structure evolution, bond strength and corrosion resistance of samples were studied. It was shown that increasing heat treatment temperature resulted in denser coating structure as well as increased interfacial residual stress. A failure mode transition from cohesive to adhesive combined with a maximum on the measured bond strength together suggested that heat treatment enhanced the cohesion strength of coating on the one hand, while deteriorated the adhesion strength of coating/substrate on the other, thus leading to the highest bond strength of 27.0MPa for the sample heat-treated at 450°C. This sample also exhibited the best corrosion resistance. Electrochemical tests revealed that relative dense coating matrix and good interfacial adhesion can effectively retard the penetration of simulated body fluid through the coating, thus providing excellent protection for the underlying magnesium alloy. Copyright © 2015 Elsevier Ltd. All rights reserved.

  3. Effects of A-Site (NaCe) Substitution with Na-Deficiency on Structures and Properties of CaBi4Ti4O15-Based High-Curie-Temperature Ceramics

    Science.gov (United States)

    Yan, Haixue; Li, Chengen; Zhou, Jiaguang; Zhu, Weimin; He, Lianxin; Song, Yuxin; Yu, Youhua

    2001-11-01

    Three kinds of bismuth-layer-structured ferroelectric (BLSF) ceramics, CaBi4Ti4O15 (CBT), Ca0.8(CeNa)0.1Bi4Ti4O15 (CNBT), and Na-deficient Ca0.8(Ce0.1Na0.05\\Box0.05)Bi4Ti4O15 [CN\\BoxBT] (where \\Box represents vacancies) were prepared by a conventional ceramic technique. X-ray powder diffraction showed that their crystal structures are a single phase of BLSF with m=4. Sintering characteristics of the three ceramics were also discussed. Scanning electron microscope (SEM) micrographs of CN\\BoxBT showed that the grain is platelike. The A-site (NaCe) substitution can improve the piezoelectric constant d33 and high-temperature resistivity with decreasing Curie temperature. The modification by A-site (NaCe) substitution with Na-deficiency is more pronounced than CNBT, which not only leads to a very high piezoelectric constant d33 and high-temperature resistivity but also increases the Curie temperature. The reason for the high Tc (Tc=866°C) of CN\\BoxBT is considered to be internal stress. As a result, Na-deficient CN\\BoxBT ceramic is found to be an excellent high-temperature piezoelectric material.

  4. In vitro evaluation of fracture resistance of teeth restored with ceramic inlays by two undercut elimination techniques

    Directory of Open Access Journals (Sweden)

    Mirzayi M.

    2008-12-01

    Full Text Available "nBackground and Aim: Polymerization shrinkage of resin cements during setting leads to stress on teeth receiving indirect esthetic restorations. Some methods like blocking out undercuts during cavity preparation with glass Ionomer can reduce the mass of resin cement and therefore the amount of stress. The aim of this study was to evaluate the fracture resistance of molar teeth, receiving class I ceramic inlays with two different methods of blocking out undercut. "nMaterials and Methods: In this experimental study, thirty intact molar teeth were randomly divided into three groups of 10 each. One group was maintained intact as the control group. Similar class I cavities with identical undercuts were prepared on the other groups. In group 2 the undercut was filled with light cured glass Ionomer (vitremer 3M before making impression, and in group 3 they were blocked out in the lab before preparation of the inlay. All the teeth in test groups were restored with indirect ceramic inlays.(vitadur - Alpha/ single bond / Rely X ARC. After thermocycling load causing fracture was assessed by universal testing machine. All the specimens were examined under a steriomicroscope (X40 to determine type of fracture. The results were analyzed by one way ANOVA and Tukey HSD tests. P< 0.05 was considered as the level of significance. "nResults: The restored groups showed significantly less fracture resistance than the control group. The difference between two test groups was not significant. The fracture in group2 had less destruction. "nConclusion: According to the findings of this study, blocking out the undercut with two different methods (using glass ionomer/ or blocking it out on the die made no diferrence in fracture resistance.

  5. A silver ion-doped calcium phosphate-based ceramic nanopowder-coated prosthesis increased infection resistance.

    Science.gov (United States)

    Kose, Nusret; Otuzbir, Ali; Pekşen, Ceren; Kiremitçi, Abdurrahman; Doğan, Aydin

    2013-08-01

    Despite progress in surgical techniques, 1% to 2% of joint arthroplasties become complicated by infection. Coating implant surfaces with antimicrobial agents have been attempted to prevent initial bacterial adhesion to implants with varying success rates. We developed a silver ion-containing calcium phosphate-based ceramic nanopowder coating to provide antibacterial activity for orthopaedic implants. We asked whether titanium prostheses coated with this nanopowder would show resistance to bacterial colonization as compared with uncoated prostheses. We inserted titanium implants (uncoated [n = 9], hydroxyapatite-coated [n = 9], silver-coated [n = 9]) simulating knee prostheses into 27 rabbits' knees. Before implantation, 5 × 10(2) colony-forming units of Staphylococcus aureus were inoculated into the femoral canal. Radiology, microbiology, and histology findings were quantified at Week 6 to define the infection, microbiologically by increased rate of implant colonization/positive cultures, histologically by leukocyte infiltration, necrosis, foreign-body granuloma, and devitalized bone, and radiographically by periosteal reaction, osteolysis, or sequestrum formation. Swab samples taken from medullary canals and implants revealed a lower proportion of positive culture in silver-coated implants (one of nine) than in uncoated (eight of nine) or hydroxyapatite-coated (five of nine) implants. Silver-coated implants also had a lower rate of colonization. No cellular inflammation or foreign-body granuloma was observed around the silver-coated prostheses. Silver ion-doped ceramic nanopowder coating of titanium implants led to an increase in resistance to bacterial colonization compared to uncoated implants. Silver-coated orthopaedic implants may be useful for resistance to local infection but will require in vivo confirmation.

  6. Comparative Study of Wear Resistance of the Composite with Microhybrid Structure and Nanocomposite

    Directory of Open Access Journals (Sweden)

    Pieniak Daniel

    2016-12-01

    Full Text Available The aim of the study was to compare microhardness and wear resistance of ceramic-polymer composites with micro and nano-hybrid structure. For the studies commercial composites were used, containing filler particles of the same type but different sizes, nano-sized (Filtek Ultimate and micro-sized (Filtek Z250 composites. Tribological testing was conducted using ball-on-disc micro-tribometer. Vickers testing method was applied for microhardness studies with the use of Futertech FM 700 device. It has been demonstrated that the wear of Filtek Ultimate is almost twice lower in comparison to wear of Filtek Z250 composite. It has been concluded that the use of filler nanoparticles significantly increased wear resistance of the material. Additionally, lack of correlation between material microhardness and wear resistance has been demonstrated.

  7. Synthesis and Structural Studies of Er3+ Containing Lead Cadmium Fluoroborate Glasses and Glass-Ceramics

    Directory of Open Access Journals (Sweden)

    Silva Maurício A.P.

    2002-01-01

    Full Text Available The vitreous domain was established in the PbF2-CdF2-B2O 3 system from melting and quenching experiments. Er3+ containing glasses were prepared and glass ceramics were obtained by selected heat-treatments. Lead fluoride was identified (beta-PbF2 as the crystalline phase. Structural studies were performed in some glassy and partially crystallized samples by means of X-ray Diffraction (XRD and Extended X-ray Absorption Fine Structure (EXAFS measurements. The role of Cd2+ and Pb2+ atoms on the glass network formation and also on the crystallization behavior was put forward by these techniques. After crystallization Er3+ atoms segregated in the crystal phase.

  8. Structural Design of Glass and Ceramic Components for Space System Safety

    Science.gov (United States)

    Bernstein, Karen S.

    2007-01-01

    Manned space flight programs will always have windows as part of the structural shell of the crew compartment. Astronauts and cosmonauts need to and enjoy looking out of the spacecraft windows at Earth, at approaching vehicles, at scientific objectives and at the stars. With few exceptions spacecraft windows have been made of glass, and the lessons learned over forty years of manned space flight have resulted in a well-defined approach for using this brittle, unforgiving material in NASA's vehicles, in windows and other structural applications. This chapter will outline the best practices that have developed at NASA for designing, verifying and accepting glass (and ceramic) windows and other components for safe and reliable use in any space system.

  9. Low-activation structural ceramic composites for fusion power reactors: materials development and main design issues

    International Nuclear Information System (INIS)

    Perez, A.S.; Le Bars, N.; Giancarli, L.; Proust, E.; Salavy, J.F.

    1994-01-01

    Development of advanced Low-Activation Materials (LAMs) with favourable short-term activation characteristics is discussed, for the use as structural materials in a fusion power reactor (in order to reduce the risk associated with a major accident, in particular those related with radio-isotopes release in the environment), and to try to approach the concept of an inherently safe reactor. LA Ceramics Composites (LACCs) are the most promising LAMs because of their relatively good thermo-mechanical properties. At present, SiC/SiC composite is the only LACC considered by the fusion community, and therefore is the one having the most complete data base. The preliminary design of a breeding blanket using SiC/SiC as structural material indicated that significant improvement of its thermal conductivity is required. (author) 11 refs.; 3 figs

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

    Energy Technology Data Exchange (ETDEWEB)

    Ching, Wai-Yim

    2012-01-14

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

  11. Triblock copolymer gels - structure, fracture behavior and application in ceramic processing

    Science.gov (United States)

    Seitz, Michelle E.

    Acrylic triblock copolymer gels transition rapidly from free-flowing liquids to elastic solids and their nanoscale self-assembly leads to reproducible structure and properties. They are an ideal model system for understanding the link between gel structure and the deformation and fracture behavior of soft, self-assembled materials. While a basic understanding of gel structure and linear viscoelastic response exists, this research aims to extend this understanding to include the nonlinear mechanical response and fracture behavior as well as the effect of gel concentration, block length, endblock fraction, and homopolymer solubilization. This expanded understanding will be applied to optimize triblock design for the thermoreversible gelcasting of ceramics. Gel structure was characterized using small angle scattering and self-consistent field theory simulations while mechanical properties were studied using a combination of rheology, swelling, indentation, uniaxial compression, and fracture experiments. Birefringence and shear alignment were used to differentiate between spherical and cylindrical micelle morphologies. An effective energy barrier of 550 kJ/mol describes gels relaxation behavior over a 40°C temperature range where the relaxation times vary by a factor of 1010. At high endblock contents, gels exhibit greater permanent deformation and moduli over an order of magnitude larger than would be expected from rubber elasticity alone due to a transition from spherical to cylindrical micelles. The rate dependence of a gels energy release rate, G , is independent of the gel concentration when G is normalized by the small strain Young's modulus, E. The gels exhibit a transition from rough, slow crack propagation to smooth, fast crack propagation for a well-defined value of the characteristic length, G /E. Crack tip stresses become highly anisotropic at stress values below the failure strength of the gels and are poorly described using linear elastic fracture

  12. Structural analysis of Fe–Mn–O nanoparticles in glass ceramics by small angle scattering

    Energy Technology Data Exchange (ETDEWEB)

    Raghuwanshi, Vikram Singh, E-mail: vikram.raghuwanshi@helmholtz-berlin.de [Helmholtz Zentrum Berlin für Materialien und Energie, Hahn-Meitner Platz 1, D-14109 Berlin (Germany); Harizanova, Ruzha [University of Chemical Technology and Metallurgy, 8 Kl. Ohridski Blvd, 1756 Sofia (Bulgaria); Tatchev, Dragomir [Institute of Physical Chemistry, Bulgarian Academy of Sciences, Acad. G. Bonchev Str. Bl. 11, 1113 Sofia (Bulgaria); Hoell, Armin [Helmholtz Zentrum Berlin für Materialien und Energie, Hahn-Meitner Platz 1, D-14109 Berlin (Germany); Rüssel, Christian [Friedrich Schiller University, Fraunhoferstr. 6, 07743 Jena (Germany)

    2015-02-15

    Magnetic nanocrystals containing Fe and Mn were obtained by annealing of silicate glasses with the composition 13.6Na{sub 2}O–62.9SiO{sub 2}–8.5MnO–15.0Fe{sub 2}O{sub 3−x} (mol%) at 580 °C for different periods of time. Here, we present Small Angle Neutron Scattering using Polarized neutrons (SANSPOL) and Anomalous Small Angle X-ray Scattering (ASAXS) investigation on these glass ceramic samples. Analysis of scattering data from both methods reveals the formation of spherical core–shell type of nanoparticles with mean sizes between 10 nm and 100 nm. ASAXS investigation shows the particles have higher concentration of iron atoms and the shell like region surrounding the particles is enriched in SiO{sub 2}. SANSPOL investigation shows the particles are found to be magnetic and are surrounded by a non-magnetic shell-like region. - Graphical abstract: Magnetic spherical core–shell nanoparticles in glass ceramics: SANSPOL and ASAXS investigations. - Highlights: • Formation and growth mechanisms of magnetic nanoparticles in silicate glass. • SANSPOL and ASAXS methods employed to evaluate quantitative information. • Analyses showed formation of nanoparticles with spherical core–shell structures. • Core of the particle is magnetic and surrounded by weak magnetic shell like region.

  13. Experimental and theoretical approaches on thermal and structural properties of Zn doped BSCCO glass ceramics

    Directory of Open Access Journals (Sweden)

    Koralay H.

    2016-03-01

    Full Text Available Thermal properties of Cu–Zn partially substituted Bi1.8Sr2Ca2Cu3.2-xZnxO10+δ (x = 0, 0.1 and 0.5 glass-ceramic systems have been investigated with the help of a differential thermal analyzer (DTA by using Johnson-Mehl-Avrami-Kolmogorov (JMAK approximation. Non-isothermal crystallization kinetics of the samples has been tested. The calculated values of activation energy of crystallization (E and Avrami parameter (n ranged between 306.1 and 338.3 kJ.mol-1 and 1.29 and 3.59, respectively. Crystallization kinetics was compared following the partial substitution, before and after Zn doping of the sample. In addition, by using a scanning electron microscope (SEM and X-ray powder diffractometer (XRD, structural properties of Zn doped BSCCO glass-ceramic samples were determined. Surface morphology of the samples was studied by SEM measurements. Lattice parameters and volume of the samples were calculated from the XRD measurements.

  14. Fabrication of unglazed ceramic tile using dense structured sago waste and clay composite

    International Nuclear Information System (INIS)

    Aripin; S Tani; S Mitsudo; T Saito; T Idehara

    2010-01-01

    In Indonesia, the sago processing industry generates every year huge amount of sago waste, and converting this waste into a useful material is possible. In the present study, physical properties of dense structured sago waste and clay composite were investigated in order to study the feasibility of reuse this sample as raw material in the producing of ceramics. Firstly, the chemical composition of ash (obtained from the sago waste) and clay was characterized. The prepared sample was sintered at the temperature range from 800 to 1,200 °C using electric furnace. The density, linear shrinkage and water absorption of the sintered sample were determined by using the Archimedes' method. The experimental result indicated that the density of the sintered sample increased with increasing sintering temperature up to 1100°C and then slightly decreased afterward. The water absorption of the products decreased with an increase in sintering temperature. In the sintered sample at 1,100 °C, the water absorption decreased rapidly and water adsorption of less than 1 % was achieved. This water absorption was less than 5 % which was needed for unglazed floor tile. The result of water adsorption suggest that it is possible to use this sample as a raw material for producing the ceramic floor tile. (author)

  15. STRUCTURAL, DIELECTRIC AND MAGNETIC PROPERTIES OF Fe-DOPED SrZrO₃ CERAMICS

    Directory of Open Access Journals (Sweden)

    Chunhong Tang

    2016-03-01

    Full Text Available SrZrO₃-based perovskite oxides have been extensively studied for their outstanding physical characteristics, chemical stability, and mechanical properties. With the recent development of multiferroics, room temperature ferromagnetism is expected to be introduced to ferroelectric or dielectric materials by magnetic ion doping in order to obtain single-phase magnetoelectric or magnetodielectric materials. In this work, SrZrO₃ and SrZr0.9375Fe0.0625O3 ceramics were fabricated by a conventional solid-state reaction method. Their structural, dielectric and magnetic properties were carefully investigated. It was found that Fe-doping could effectively improve the dielectric constant of SrZrO₃. Moreover, ferromagnetism with a Curie temperature of about 685 K was successfully introduced by a small amount of Fe dopant. The saturation magnetization and coercive field of SrZrO₃ and SrZr0.9375Fe0.0625O3 ceramics were 3.0 emu/g and 1.3 kOe, respectively, at room temperature. The origin and mechanism of ferromagnetism introduced by Fe dopant is discussed based on the valence fluctuation of Fe ions.

  16. Structural analysis of Fe–Mn–O nanoparticles in glass ceramics by small angle scattering

    International Nuclear Information System (INIS)

    Raghuwanshi, Vikram Singh; Harizanova, Ruzha; Tatchev, Dragomir; Hoell, Armin; Rüssel, Christian

    2015-01-01

    Magnetic nanocrystals containing Fe and Mn were obtained by annealing of silicate glasses with the composition 13.6Na 2 O–62.9SiO 2 –8.5MnO–15.0Fe 2 O 3−x (mol%) at 580 °C for different periods of time. Here, we present Small Angle Neutron Scattering using Polarized neutrons (SANSPOL) and Anomalous Small Angle X-ray Scattering (ASAXS) investigation on these glass ceramic samples. Analysis of scattering data from both methods reveals the formation of spherical core–shell type of nanoparticles with mean sizes between 10 nm and 100 nm. ASAXS investigation shows the particles have higher concentration of iron atoms and the shell like region surrounding the particles is enriched in SiO 2 . SANSPOL investigation shows the particles are found to be magnetic and are surrounded by a non-magnetic shell-like region. - Graphical abstract: Magnetic spherical core–shell nanoparticles in glass ceramics: SANSPOL and ASAXS investigations. - Highlights: • Formation and growth mechanisms of magnetic nanoparticles in silicate glass. • SANSPOL and ASAXS methods employed to evaluate quantitative information. • Analyses showed formation of nanoparticles with spherical core–shell structures. • Core of the particle is magnetic and surrounded by weak magnetic shell like region

  17. Structural properties of a bone-ceramic composite as a promising material in spinal surgery

    Energy Technology Data Exchange (ETDEWEB)

    Kirilova, I. A., E-mail: IKirilova@mail.ru; Sadovoy, M. A.; Podorozhnaya, V. T., E-mail: VPodorognaya@niito.ru; Taranov, O. S. [Novosibirsk Research Institute of Traumatology and Orthopedics n.a. Ya.L. Tsivyan, Novosibirsk (Russian Federation); Klinkov, S. V.; Kosarev, V. F. [Christianovich Institute of Theoretical and Applied Mechanics, SB RAS, Novosibirsk (Russian Federation); Shatskaya, S. S. [Institute of Solid State Chemistry and Mechanochemistry, SB RAS, Novosibirsk (Russian Federation)

    2015-11-17

    The paper describes the results of in vitro tests of composite bone-ceramic implants and procedures for modifying implant surfaces to enhance osteogenesis. Analysis of CBCI ESs demonstrated that they have a porous structure with the mean longitudinal pore size of 70 µm and the mean transverse pore size of 46 µm; surface pores are open, while inner pores are closed. Elemental analysis of the CBCI surface demonstrates that CBCIs are composed of aluminum and zirconium oxides and contain HA inclusions. Profilometry of the CBCI ES surface revealed the following deviations: the maximum deviation of the profile in the sample center is 15 µm and 16 µm on the periphery, while the arithmetical mean and mean square deviations of the profile are 2.65 and 3.4 µm, respectively. In addition, CBCI biodegradation products were pre-examined; a 0.9% NaCl solution was used as a comparison group. Potentially toxic and tissue accumulated elements, such as cadmium, cobalt, mercury, and lead, are present only in trace amounts and have no statistically significant differences with the comparison group, which precludes their potential toxic effects on the macroorganism. Ceramic-based CBCI may be effective and useful in medicine for restoration of the anatomic integrity and functions of the bone tissue.

  18. Atomistic Structure, Strength, and Kinetic Properties of Intergranular Films in Ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Garofalini, Stephen H

    2015-01-08

    Intergranular films (IGFs) present in polycrystalline oxide and nitride ceramics provide an excellent example of nanoconfined glasses that occupy only a small volume percentage of the bulk ceramic, but can significantly influence various mechanical, thermal, chemical, and optical properties. By employing molecular dynamics computer simulations, we have been able to predict structures and the locations of atoms at the crystal/IGF interface that were subsequently verified with the newest electron microscopies. Modification of the chemistry of the crystal surface in the simulations provided the necessary mechanism for adsorption of specific rare earth ions from the IGF in the liquid state to the crystal surface. Such results had eluded other computational approaches such as ab-initio calculations because of the need to include not only the modified chemistry of the crystal surfaces but also an accurate description of the adjoining glassy IGF. This segregation of certain ions from the IGF to the crystal caused changes in the local chemistry of the IGF that affected fracture behavior in the simulations. Additional work with the rare earth ions La and Lu in the silicon oxynitride IGFs showed the mechanisms for their different affects on crystal growth, even though both types of ions are seen adhering to a bounding crystal surface that would normally imply equivalent affects on grain growth.

  19. Evaluation of wear resistant ceramic valve seats in gas-fueled power generation engines

    Science.gov (United States)

    Burrahm, R. W.; Branecky, R. J.; Sui, P. C.; Latusek, J. P.; Hsu, S. M.

    1994-12-01

    This project is directed at the reduction of valve recession in natural gas-fueled engines. Ceramic valve seat inserts have been procured, installed in a Caterpillar G3516 natural gas generator set, and tested for 1000 hours. Two different silicon nitride materials are being utilized for the valve seats in addition to stock Eatonite metallic inserts. Three valve face materials are being tested. These include stock Caterpillar stellite 1 faced, stellite 6 faced, and unfaced valves. A test matrix was used to allow comparison of all three valve face materials in combination with all three insert materials. The testing is scheduled to continue for an additional 7000 hours. No problems have been encountered with the test materials. In general, it has been shown that two types of silicon nitride materials have at least short term durability in engine operation. Neither material has exhibited any deficiencies thus far. An economic analysis spreadsheet has been created to calculate potential cost savings potential using ceramic valve seat inserts. Valve recession data for the first 1000 hours shows expected trends. Exhaust valve positions are wearing more than intake valve positions. If the intake positions and all positions with unfaced valve are ignored, then ceramic inserts paired with Stellite 1 valves show the most wear.

  20. Study and selection of structured packing material: metallic, polymeric or ceramic to operate a column of absorption polluting gases coming from brick kilns efficiently

    International Nuclear Information System (INIS)

    Salazar P, A.

    2012-01-01

    In this research three structured packing materials were characterized: a metallic, polymeric and ceramic. The study of the physical properties of structured packing materials, and their behavior within the absorption column allowed to suggest a gas-liquid contactor material with higher mechanical and chemical resistance, which is more efficient for the treatment of sour gases from brick kilns. To study the mechanical properties (hardness, tension and elastic modulus) were used procedures of the American Society for Testing Materials, as well as resistance to corrosion. The geometric characteristics, the density, the melting temperature and the weight were tested with procedures of the measuring equipment. The structure was evaluated by X-ray diffraction, morphology was observed by scanning electron microscopy coupled to a sound of dispersive energy of X-ray, to quantify elemental chemical composition. The interaction of gas-liquid contactors materials in presence of CO 2 , was evaluated in three absorption columns built of Pyrex glass, with a diameter of 0.1016 m, of 1.5 m in height, 0.0081m 2 cross-sectional area, packed with every kind of material: metallic, polymeric and ceramic, processing a gas flow of 20m 3 / h at 9% CO 2 , in air and a liquid flow to 30% of Mea 5 L/min. The results of the properties studied were by the metallic material: more density, higher roughness, the greater tensile strength, greater resistance to corrosion in the presence of an aqueous solution of monoethanolamine (Mea) to 30% by weight, improvement more efficient absorption of CO 2 , and higher modulus of elasticity. The polymeric material was characterized to have lower hardness, lower roughness, lower density, lower melting temperature, greater resistance to corrosion in the presence of 1 N H 2 SO 4 aqueous solution, and allowed an absorption efficiency of CO 2 , 2% lower than that presented by the material metallic. The ceramic material found to be the hardest of the three

  1. Structural Reliability of Ceramics at High Temperature: Mechanisms of Fracture and Fatigue Crack Growth

    Energy Technology Data Exchange (ETDEWEB)

    Reinhold H. Dauskardt

    2005-08-01

    Final report of our DOE funded research program. Aim of the research program was to provide a fundamental basis from which the mechanical reliability of layered structures may be understood, and to provide guidelines for the development of technologically relevant layered material structures with optimum resistance to fracture and subcritical debonding. Progress in the program to achieve these goals is described.

  2. Synthesis, structural and microwave dielectric properties of Al2W3-xMoxO12 (x = 0-3) ceramics

    International Nuclear Information System (INIS)

    Surjith, A.; James, Nijesh K.; Ratheesh, R.

    2011-01-01

    Highlights: → Solid state synthesis of phase pure Al 2 W 3-x Mo x O 12 (x = 0-3) compositions. → Sintering studies of Al 2 W 3-x Mo x O 12 (x = 0-3) ceramics. → Structural and microstructural evaluation using powder X-ray diffraction and SEM studies. → Microwave dielectric property evaluation of Al 2 W 3-x Mo x O 12 (x = 0-3) ceramics through Hakki and Coleman post resonator and cavity perturbation techniques. → Structure-property correlation through Laser Raman studies. - Abstract: Low dielectric ceramics in the Al 2 W 3-x Mo x O 12 (x = 0-3) system have been prepared through solid state ceramic route. The phase purity of the ceramic compositions has been studied using powder X-ray diffraction (XRD) studies. The microstructure of the sintered ceramics was evaluated by Scanning Electron Microscopy (SEM). The crystal structure of the ceramic compositions as a result of Mo substitution has been studied using Laser Raman spectroscopy. The microwave dielectric properties of the ceramics were studied by Hakki and Coleman post resonator and cavity perturbation techniques. Al 2 Mo x W 3-x O 12 (x = 0-3) ceramics exhibited low dielectric constant and relatively high unloaded quality factor. The temperature coefficient of resonant frequency of the compositions is found to be in the range -41 to -72 ppm/deg. C.

  3. Evaluation of Mechanical Properties and Structural Changes of Ceramic Filter Materials for Hot Gas Cleaning under Simulated Process Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Westerheide, R.; von der Wehd, C.; Adler, J.; Rehak, P.

    2002-09-19

    The objective of this study is to evaluate changes in structure and mechanical properties of ceramic filter materials under simulated corrosive process conditions. Due to an analysis of the mechanisms of degradation firstly an optimization of materials shall be enabled and secondly a material selection for specific applications shall be relieved. This publication describes the investigations made on many ceramic support materials based on oxides and carbides. Both commercially available and newly developed support materials have been evaluated for specific applications in hot gas cleaning.

  4. The Alarcos settlement (Ciudad Real in the early first millennium BC: Structures and ceramics

    Directory of Open Access Journals (Sweden)

    M.ª del Rosario García Huerta

    2017-07-01

    Full Text Available The final Bronze Age and Early Iron Age of the south-western Meseta were insufficiently documented to be properly characterized until the final years of the 20th century. However, recent work at settlements such as Alarcos (Ciudad Real has obtained valuable information about the habitat structures and a large amount of well contextualized archaeological material (mainly pottery painted after firing. These are carefully-made tablewares whose decoration indicates a selective adoption of fashions and customs of Tartessian inspiration (e.g., Carambolo type and burnished-lattice ceramics as consequence of commercial exchanges. This new data is helping us achieve a better understanding of the new settlement patterns that started to appear at that time in the middle valley of the Guadiana river and shows the dynamism of the communities located there.

  5. Structure and performance of polymer-derived bulk ceramics determined by method of filler incorporation

    Science.gov (United States)

    Konegger, T.; Schneider, P.; Bauer, V.; Amsüss, A.; Liersch, A.

    2013-12-01

    The effect of four distinct methods of incorporating fillers into a preceramic polymer matrix was investigated with respect to the structural and mechanical properties of the resulting materials. Investigations were conducted with a polysiloxane/Al2O3/ZrO2 model system used as a precursor for mullite/ZrO2 composites. A quantitative evaluation of the uniformity of filler distribution was obtained by employing a novel image analysis. While solvent-free mixing led to a heterogeneous distribution of constituents resulting in limited mechanical property values, a strong improvement of material homogeneity and properties was obtained by using solvent-assisted methods. The results demonstrate the importance of the processing route on final characteristics of polymer-derived ceramics.

  6. Power Law Versus Exponential Form of Slow Crack Growth of Advanced Structural Ceramics: Dynamic Fatigue

    Science.gov (United States)

    Choi, Sung R.; Gyekenyesi, John P.

    2002-01-01

    The life prediction analysis based on an exponential crack velocity formulation was examined using a variety of experimental data on glass and advanced structural ceramics in constant stress-rate ("dynamic fatigue") and preload testing at ambient and elevated temperatures. The data fit to the strength versus In (stress rate) relation was found to be very reasonable for most of the materials. It was also found that preloading technique was equally applicable for the case of slow crack growth (SCG) parameter n > 30. The major limitation in the exponential crack velocity formulation, however, was that an inert strength of a material must be known priori to evaluate the important SCG parameter n, a significant drawback as compared to the conventional power-law crack velocity formulation.

  7. Fine structuration of low-temperature co-fired ceramic (LTCC) microreactors.

    Science.gov (United States)

    Jiang, Bo; Haber, Julien; Renken, Albert; Muralt, Paul; Kiwi-Minsker, Lioubov; Maeder, Thomas

    2015-01-21

    The development of microreactors that operate under harsh conditions is always of great interest for many applications. Here we present a microfabrication process based on low-temperature co-fired ceramic (LTCC) technology for producing microreactors which are able to perform chemical processes at elevated temperature (>400 °C) and against concentrated harsh chemicals such as sodium hydroxide, sulfuric acid and hydrochloric acid. Various micro-scale cavities and/or fluidic channels were successfully fabricated in these microreactors using a set of combined and optimized LTCC manufacturing processes. Among them, it has been found that laser micromachining and multi-step low-pressure lamination are particularly critical to the fabrication and quality of these microreactors. Demonstration of LTCC microreactors with various embedded fluidic structures is illustrated with a number of examples, including micro-mixers for studies of exothermic reactions, multiple-injection microreactors for ionone production, and high-temperature microreactors for portable hydrogen generation.

  8. Structure, composition and function of interfaces in ceramic fibre/matrix composites

    International Nuclear Information System (INIS)

    Pippel, E.

    1993-01-01

    Improving the properties of fibre reinforced ceramics and glasses by optimizing their microstructure requires the knowledge of this structure down to the atomic level. In these materials energy-dissipative processes during fracture particularly act within an interface layer or layer system between fibre and matrix which can either be produced by fibre coating, or which develops during the processing of the composites. Examples are presented of the microstructural phenomena of such layers revealed by HVEM and HREM and complemented by microchemical information via a nanoscale EDXS equipment. The investigations are carried out on Nicalon fibres in Duran glass as well as on Tyranno, Nicalon and carbon fibres in different SiC-matrices. Finally, a process is discussed which may control the important interface parameters. (orig.)

  9. Smart structures for application in ceramic barrier filter technology. Final report, August 1991--August 1994

    Energy Technology Data Exchange (ETDEWEB)

    Weinstein, S.J.; Lippert, T.E

    1994-12-01

    High temperature optical fiber sensors were developed to measure the in-service stressing that occurs in ceramic barrier filter systems. The optical fiber sensors were based on improvements to the sensor design developed under the DOE/METC Smart Structures for Fossil Energy Applications contract no. DE-AC21-89MC25159. In-house application testing of these sensors on both candle and cross-flow filters were performed in the Westinghouse Science and Technology Center High-Temperature, High-Pressure Filter Test Facility and the results analyzed. This report summarizes the sensor developments, methods to apply the sensors to the filters for in-situ testing, and the test results from the four in-house tests that were performed.

  10. The XPS study of the structure of uranium-containing ceramics

    Directory of Open Access Journals (Sweden)

    Teterin Anton Yu.

    2010-01-01

    Full Text Available The samples of the (Ca0.5GdU0.5Zr2O7 and (Ca0.5GdU0.5(ZrTiO7 ceramics with the fluorite and pyrochlore structures used as matrixes for the long-lived high-level radioactive waste disposal were studied with the X-ray photoelectron spectroscopy method. On the basis of the X-ray photoelectron spectroscopy parameters of the outer and core electrons from the binding energy range of 0-1250 eV the oxidation states of the included metal ions were determined, the quantitative elemental and ionic analysis was done, and the orderliness (monophaseness was evaluated. The obtained data agree with the X-ray diffraction and the scanning electron microscopy results.

  11. Optimization and Characterization of Preceramic Inks for Direct Ink Writing of Ceramic Matrix Composite Structures.

    Science.gov (United States)

    Franchin, Giorgia; Maden, Halide Selin; Wahl, Larissa; Baliello, Andrea; Pasetto, Marco; Colombo, Paolo

    2018-03-28

    In a previous work, an ink based on a preceramic polymer, SiC fillers, and chopped carbon fibers was proposed for the production of Ceramic Matrix Composite (CMC) structures by Direct Ink Writing (DIW) and subsequent pyrolysis. Thanks to the shear stresses generated at the nozzle tip during extrusion, carbon fibers can be aligned along the printing direction. Fumed silica was added to the ink in order to enhance its rheological properties; however, the printed structures still showed some deformation in the Z direction. In this work, a second ink was successfully developed to limit deformation and at the same time avoid the addition of fumed silica, which limited the potential temperature of application of the composites. Instead, the positive role of the preceramic polymer on the ink rheology was exploited by increasing its concentration in the ink. Rheological characterization carried out on both inks confirmed that they possessed Bingham shear thinning behavior and fast viscosity recovery. Single filaments with different diameters (~310 µm and ~460 µm) were produced with the latter ink by DIW and subsequent pyrolysis. Tested under a four-point flexural test, the filaments showed a mean flexural strength above 30 MPa, graceful failure, and fiber pull-out. The results of this work suggest that CMC components can effectively be fabricated via DIW of a preceramic ink with embedded short fibers; the preceramic polymer is able to provide the desired rheology for the process and to develop a dense matrix capable of incorporating both fibers and ceramic particles, whereas the fibers addition contributes to an increase of the fracture toughness of the material and to the development of a graceful failure mode.

  12. Resistive field structures for semiconductor devices and uses therof

    Science.gov (United States)

    Marinella, Matthew; DasGupta, Sandeepan; Kaplar, Robert; Baca, Albert G.

    2017-09-12

    The present disclosure relates to resistive field structures that provide improved electric field profiles when used with a semiconductor device. In particular, the resistive field structures provide a uniform electric field profile, thereby enhancing breakdown voltage and improving reliability. In example, the structure is a field cage that is configured to be resistive, in which the potential changes significantly over the distance of the cage. In another example, the structure is a resistive field plate. Using these resistive field structures, the characteristics of the electric field profile can be independently modulated from the physical parameters of the semiconductor device. Additional methods and architectures are described herein.

  13. Corrosion resistance of ceramic materials in pyrochemical reprocessing atmosphere by using molten salt for spent nuclear oxide fuel. Corrosion research under chlorine gas condition

    International Nuclear Information System (INIS)

    Takeuchi, Masayuki; Hanada, Keiji; Koizumi, Tsutomu; Aose, Shinichi; Kato, Toshihiro

    2002-12-01

    Pyrochemical reprocessing using molten salts (RIAR process) has been recently developed for spent nuclear oxide fuel and discussed in feasibility study. It is required to improve the corrosion resistance of equipments such as electrolyzer because the process is operated in severe corrosion environment. In this study, the corrosion resistance of ceramic materials was discussed through the thermodynamic calculation and corrosion test. The corrosion test was basically carried out in alkali molten salt under chlorine gas condition. And further consideration about the effects of oxygen, carbon and main fission product's chlorides were evaluated in molten salt. The result of thermodynamic calculation shows most of ceramic oxides have good chemical stability on chlorine, oxygen and uranyl chloride, however the standard Gibb's free energies with carbon have negative value. On the other hand, eleven kinds of ceramic materials were examined by corrosion test, then silicon nitride, mullite and cordierite have a good corrosion resistance less than 0.1 mm/y. Cracks were not observed on the materials and flexural strength did not reduce remarkably after 480 hours test in molten salt with Cl 2 -O 2 bubbling. In conclusion, these three ceramic materials are most applicable materials for the pyrochemical reprocessing process with chlorine gas condition. (author)

  14. Structural, Raman, and dielectric studies on multiferroic Mn-doped Bi 1-xLax FeO 3 ceramics

    KAUST Repository

    Xing, Zhibiao

    2014-04-03

    Multiferroic Bi1-xLaxFeO3 [BLFO (x)] ceramics with x = 0.10-0.50 and Mn-doped BLFO (x = 0.30) ceramics with different doping contents (0.1-1.0 mol%) were prepared by solid-state reaction method. They were crystallized in a perovskite phase with rhombohedral symmetry. In the BLFO (x) system, a composition (x)-driven structural transformation (R3c→C222) was observed at x = 0.30. The formation of Bi2Fe 4O9 impure phase was effectively suppressed with increasing the x value, and the rhombohedral distortion in the BLFO ceramics was decreased, leading to some Raman active modes disappeared. A significant red frequency shift (~13 cm-1) of the Raman mode of 232 cm-1 in the BLFO ceramics was observed, which strongly perceived a significant destabilization in the octahedral oxygen chains, and in turn affected the local FeO6 octahedral environment. In the Mn-doped BLFO (x = 0.30) ceramics, the intensity of the Raman mode near 628 cm-1 was increased with increasing the Mn-doping content, which was resulted from an enhanced local Jahn-Teller distortions of the (Mn,Fe)O6 octahedra. Electron microscopy images revealed some changes in the ceramic grain sizes and their morphologies in the Mn-doped samples at different contents. Wedge-shaped 71° ferroelectric domains with domain walls lying on the {110} planes were observed in the BLFO (x = 0.30) ceramics, whereas in the 1.0 mol% Mn-doped BLFO (x = 0.30) samples, 71° ferroelectric domains exhibited a parallel band-shaped morphology with average domain width of 95 nm. Dielectric studies revealed that high dielectric loss of the BLFO (x = 0.30) ceramics was drastically reduced from 0.8 to 0.01 (measured @ 104 Hz) via 1.0 mol% Mn-doping. The underlying mechanisms can be understood by a charge disproportion between the Mn4+ and Fe2+ in the Mn-doped samples, where a reaction of Mn4+ + Fe2+→Mn3+ + Fe3+ is taken place, resulting in the reduction in the oxygen vacancies and a suppression of the electron hopping from Fe3+ to Fe2+ ions

  15. 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

  16. EFFECT OF SINTERING PROFILES ON THE PROPERTIES AND AGEING RESISTANCE OF Y-TZP CERAMIC

    Directory of Open Access Journals (Sweden)

    C.Y. Tan

    2011-12-01

    Full Text Available A commercially available Y-TZP ceramic powder was fabricated under four different sintering profiles in order to investigate the effects of conventional single-stage sintering (SSS with dwell times of 1 min and 2 h, respectively, compared with two-stage sintering (TSS, on the physical and mechanical properties of Y-TZP. Sintering was performed up to 1400oC at a ramp rate of 10oC/min. It was revealed that samples sintered via TSS yielded better properties than the SSS samples sintered at 1400oC using a dwell time of 2 h. In the hydrothermal ageing test, TSS samples did not undergo low-temperature degradation via the tetragonal to monoclinic phase transformation. Nevertheless, it was found by XRD analysis that Y-TZP ceramics sintered by the SSS method using a short dwell time of 1 min were effective in maintaining tetragonal phase stability after 50 h of exposure to superheated steam conditions.

  17. Rheological behaviour and thermal dilation effects of alumino-silicate adhesives intended for joining of high-temperature resistant sandwich structures

    Czech Academy of Sciences Publication Activity Database

    Černý, Martin; Chlup, Zdeněk; Strachota, Adam; Schweigstillová, Jana; Svítilová, Jaroslava; Halasová, Martina

    2017-01-01

    Roč. 37, č. 5 (2017), s. 2209-2218 ISSN 0955-2219 R&D Projects: GA ČR GAP107/12/2445 Grant - others:OPPK(XE) CZ.2.16/3.1.00/21538 Program:OPPK Institutional support: RVO:67985891 ; RVO:68081723 ; RVO:61389013 Keywords : Sandwich * Inorganic adhesive * Si-O-C ceramics * Ceramic foam * Ceramic fibre Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass; CD - Macromolecular Chemistry (UMCH-V); JH - Ceramics, Fire-Resistant Materials and Glass (UFM-A) OBOR OECD: Ceramics; Polymer science (UMCH-V); Ceramics (UFM-A) Impact factor: 3.411, year: 2016

  18. Theoretical studies on the electronic structure and properties of complex ceramic crystals and glasses

    Energy Technology Data Exchange (ETDEWEB)

    Ching, Wai-Yim.

    1991-01-24

    This progress report summarizes the accomplishment of the DOE-support research program at the University of Missouri-Kansas City for the period July 1, 1991--June 30, 1992. This is the second year of a three-year renewal. The major accomplishments for the year are: (a) Initiation of fundamental studies on the electronic properties of C{sub 60} and related crystals; (b) study of electronic structures and optical properties of several important ceramic crystals, especially on AlN, SiO{sub 2} and Al{sub 2}O{sub 3}; (c) first-principles calculation of total energies and structural phase transitions in oxides, nitrides, and borides; (d) theory of magnetism in Nd{sub 2}Fe{sub 14}B permanent magnetic alloy. The major focus for the next year's effort will be on the following areas: (1) Continuation of the fundamental studies on the buckminsterfullerene system with particular emphasis on the alkali-doped superconducting fullerides. (2) Fundamental studies on the structure and properties of Boron and B-related compounds. (3) Basic studies on the structural and electronic properties of metallic glasses with particular emphasis on the magnetic glasses. (4) Further development of the first-principles OLCAO method for applications to super-complex systems.

  19. An investigation into the relationship between thermal shock resistance and ballistic performance of ceramic materials

    Science.gov (United States)

    Beaumont, Robert

    Currently, there are no reliable methods for screening potential armour materials and hence full-scale ballistic trials are needed. These are both costly and time-consuming in terms of the actual test and also in the materials development that needs to take place to produce sufficient material to give a meaningful result. Whilst it will not be possible to dispense with ballistic trials before material deployment in armour applications, the ability to shorten the development cycle would be advantageous. The thermal shock performance of ceramic armour materials has been highlighted as potential marker for ballistic performance. Hence the purpose of this study was to investigate this further. A new thermal shock technique that reproduced features relevant to ballistic testing was sought. As it would be beneficial to have a simple test that did not use much material, a water-drop method was adopted. This was combined with a variety of characterisation techniques, administered pre- and post-shock. The methods included measurement of the amplitude of ultrasonic wave transmission through the sample alongside residual strength testing using a biaxial ball-on-ball configuration and reflected light and confocal microscopy. Once the protocols had been refined the testing regime was applied to a group of ceramic materials. The materials selected were from two broad groups: alumina and carbide materials. Carbide ceramics show superior performance to alumina ceramics in ballistic applications so it was essential that any screening test would be easily able to differentiate the two groups. Within the alumina family, two commercially available materials, AD995 and Sintox FA, were selected. These were tested alongside three developmental silicon carbide-boron carbide composites, which had identical chemical compositions but different microstructures and thus presented more of a challenge in terms of differentiation. The results from the various tests were used to make predictions

  20. All-Ceramic Single Crown Restauration of Zirconia Oral Implants and Its Influence on Fracture Resistance: An Investigation in the Artificial Mouth

    Directory of Open Access Journals (Sweden)

    Ralf-Joachim Kohal

    2015-04-01

    Full Text Available The aim of the current investigation was to evaluate the fracture resistance of one-piece zirconia oral implants with and without all-ceramic incisor crowns after long-term thermomechanical cycling. A total of 48 implants were evaluated. The groups with crowns (C, 24 samples and without crowns (N, 24 samples were subdivided according to the loading protocol, resulting in three groups of 8 samples each: Group “0” was not exposed to cyclic loading, whereas groups “5” and “10” were loaded with 5 and 10 million chewing cycles, respectively. This resulted in 6 different groups: C0/N0, C5/N5 and C10/N10. Subsequently, all 48 implants were statically loaded to fracture and bending moments were calculated. All implants survived the artificial aging. For the static loading the following average bending moments were calculated: C0: 326 Ncm; C5: 339 Ncm; C10: 369 Ncm; N0: 339 Ncm; N5: 398 Ncm and N10: 355 Ncm. To a certain extent, thermomechanical cycling resulted in an increase of fracture resistance which did not prove to be statistically significant. Regarding its fracture resistance, the evaluated ceramic implant system made of Y-TZP seems to be able to resist physiological chewing forces long-term. Restauration with all-ceramic single crowns showed no negative influence on fracture resistance.

  1. Fine structure analysis of biocompatible ceramic materials based hydroxyapatite and metallic biomaterials 316L

    International Nuclear Information System (INIS)

    Anghelina, F.V.; Ungureanu, D.N.; Bratu, V.; Popescu, I.N.; Rusanescu, C.O.

    2013-01-01

    The aim of this paper was to obtain and characterize (surface morphology and fine structure) two types of materials: Ca 10 (PO 4 ) 6 (OH) 2 hydroxyapatite powder (HAp) as biocompatible ceramic materials and AISI 316L austenitic stainless steels as metallic biomaterials, which are the components of the metal–ceramic composites used for medical implants in reconstructive surgery and prosthetic treatment. The HAp was synthesized by coprecipitation method, heat treated at 200 °C, 800 °C and 1200 °C for 4 h, analyzed by X-ray diffraction (XRD) and scanning electron microscope (SEM). The stainless steel 316L type was made by casting, annealing and machined with a low speed (100 mm/s) in order to obtain a smooth surface and after that has been studied from residual stresses point of view in three polishing regimes conditions: at low speed polishing (150 rpm), at high speed polishing (1500 rpm) and high speed-vibration contact polishing (1500 rpm) using wide angle X-ray diffractions (WAXD). The chemical compositions of AISI 316 steel samples were measured using a Foundry Master Spectrometer equipped with CCD detector for spectral lines and the sparking spots of AISI 316L samples were analyzed using SEM. By XRD the phases of HAp powders have been identified and also the degree of crystallinity and average size of crystallites, and with SEM, we studied the morphology of the HAp. It has been found from XRD analysis that we obtained HAp with a high degree of crystallinity at 800 °C and 1200 °C, no presence of impurity and from SEM analysis we noticed the influence of heat treatment on the ceramic particles morphology. From the study of residual stress profiles of 316L samples were observed that it differs substantially for different machining regimes and from the SEM analysis of sparking spots we revealed the rough surfaces of stainless steel rods necessary for a better adhesion of HAp on it.

  2. Comparative characterization of a novel cad-cam polymer-infiltrated-ceramic-network.

    Science.gov (United States)

    Albero, Alberto; Pascual, Agustín; Camps, Isabel; Grau-Benitez, María

    2015-10-01

    The field of dental ceramics for CAD-CAM is enriched with a new innovative material composition having a porous three-dimensional structure of feldspathic ceramic infiltrated with acrylic resins.The aim of this study is to determine the mechanical properties of Polymer-Infiltrated-Ceramic-Network (PICN) and compare its performance with other ceramics and a nano-ceramic resin available for CAD-CAM systems. In this study a total of five different materials for CAD-CAM were investigated. A polymer-infiltrated ceramic (Vita Enamic), a nano-ceramic resin (Lava Ultimate), a feldspathic ceramic (Mark II), a lithium disilicate ceramic (IPS-e max CAD) and finally a Leucite based ceramic (Empress - CAD). From CAD-CAM blocks, 120 bars (30 for each material cited above) were cut to measure the flexural strength with a three-point-bending test. Strain at failure, fracture stress and Weibull modulus was calculated. Vickers hardness of each material was also measured. IPS-EMAX presents mechanical properties significantly better from the other materials studied. Its strain at failure, flexural strength and hardness exhibited significantly higher values in comparison with the others. VITA ENAMIC and LAVA ULTIMATE stand out as the next most resistant materials. The flexural strength, elastic modulus similar to a tooth as well as having less hardness than ceramics make PICN materials an option to consider as a restorative material. Ceramic infiltrated with resin, CAD-CAM, Weibull modulus, flexural strength, micro hardness.

  3. Optimization of PZT ceramic IDT sensors for health monitoring of structures.

    Science.gov (United States)

    Takpara, Rafatou; Duquennoy, Marc; Ouaftouh, Mohammadi; Courtois, Christian; Jenot, Frédéric; Rguiti, Mohamed

    2017-08-01

    Surface acoustic waves (SAW) are particularly suited to effectively monitoring and characterizing structural surfaces (condition of the surface, coating, thin layer, micro-cracks…) as their energy is localized on the surface, within approximately one wavelength. Conventionally, in non-destructive testing, wedge sensors are used to the generation guided waves but they are especially suited to flat surfaces and sized for a given type material (angle of refraction). Additionally, these sensors are quite expensive so it is quite difficult to leave the sensors permanently on the structure for its health monitoring. Therefore we are considering in this study, another type of ultrasonic sensors, able to generate SAW. These sensors are interdigital sensors or IDT sensors for InterDigital Transducer. This paper focuses on optimization of IDT sensors for non-destructive structural testing by using PZT ceramics. The challenge was to optimize the dimensional parameters of the IDT sensors in order to efficiently generate surface waves. Acoustic tests then confirmed these parameters. Copyright © 2017 Elsevier B.V. All rights reserved.

  4. Resistance-Based Ceramic Ho123 Ionic Conductor for Oxygen Gas Sensing

    Science.gov (United States)

    Idrus, L. H.; Yahya, A. K.

    2009-07-01

    Oxygen sensing properties of HoBa2Cu3O7-δ ceramic rods utilizing hot-spot phenomenon have been characterized. The rods were prepared from high purity oxides using the conventional solid-state reaction method. I-V characterization showed increase in output current with voltage before the appearance of the hot spot. After the appearance of the hot-spot, the output current strongly depended on oxygen partial pressure. The rod showed stable sensing characteristics with good electrical stability and reproducibility with higher sensitivity at low oxygen partial pressure. The sensing property is associated with the absorption of oxygen and dissociation into holes and oxide ions. Ho123 is more sensitive at pO2 below 20% compared to Er123 possibly due to differences in oxygen activation energy related to RE ionic radius.

  5. Resistance-Based Ceramic Ho123 Ionic Conductor for Oxygen Gas Sensing

    International Nuclear Information System (INIS)

    Idrus, L. H.; Yahya, A. K.

    2009-01-01

    Oxygen sensing properties of HoBa 2 Cu 3 O 7-δ ceramic rods utilizing hot-spot phenomenon have been characterized. The rods were prepared from high purity oxides using the conventional solid-state reaction method. I-V characterization showed increase in output current with voltage before the appearance of the hot spot. After the appearance of the hot-spot, the output current strongly depended on oxygen partial pressure. The rod showed stable sensing characteristics with good electrical stability and reproducibility with higher sensitivity at low oxygen partial pressure. The sensing property is associated with the absorption of oxygen and dissociation into holes and oxide ions. Ho123 is more sensitive at pO 2 below 20% compared to Er123 possibly due to differences in oxygen activation energy related to RE ionic radius.

  6. A sputtered zirconia primer for improved thermal shock resistance of plasma-sprayed ceramic turbine seals

    Science.gov (United States)

    Bill, R. C.; Sovey, J.; Allen, G. P.

    1981-01-01

    It is shown that the application of sputtered Y2O3-stabilized ZrO2 (YSZ) primer in plasma-sprayed YSZ ceramic-coated turbine blades results in an improvement, by a factor of 5-6, in the thermal shock life of specimens with a sprayed, porous, Ni-Cr-Al-Y intermediate layer. Species with and without the primer were found to be able to survive 1000 cycles when the intermediate layer was used, but reduced laminar cracking was observed in the specimen with the primer. It is suggested that the sputtered YZS primer-induced properties are due to (1) more effective wetting and adherence of the plasma-sprayed YZS particles to the primer, and (2) the primer's retardation of impinging, molten plasma sprayed particles solidification rates, which result in a less detrimental residual stress distribution.

  7. Effect of Veneering Methods on Zirconia Framework-Veneer Ceramic Adhesion and Fracture Resistance of Single Crowns.

    Science.gov (United States)

    Kanat-Ertürk, Burcu; Çömlekoğlu, Erhan M; Dündar-Çömlekoğlu, Mine; Özcan, Mutlu; Güngör, Mehmet Ali

    2015-12-01

    The aim of this study was to evaluate the fracture resistance (FR) and shear bond strength (SBS) via finite element analysis (FEA) of zirconia framework veneered with different methods. Zirconia frameworks were prepared as crowns for FR and cubic blocks for SBS (N = 60, n = 10). The specimens were veneered with one of the following veneering methods: (a) overcemented file-splitting (OCF), (b) layering (L), or (c) overpressing (P). For crowns, stainless steel dies (N = 30; chamfer: 1 mm) were scanned using a contrast spray. Bilayered design for OCF and reduced design (1 mm) for both L and P were performed by computer-aided design and manufacturing. For the SBS test, zirconia blocks were sectioned (4 × 4 × 4 mm(3)) under water cooling and sintered. Frameworks were veneered with compatible ceramics for each veneering method and subjected to mechanical tests. The milled suprastructures were bonded to zirconia frameworks using a resin composite in Group OCF and photopolymerized. Crowns were cemented to the metal dies with resin modified glass-ionomer cement. All specimens were stored at 37°C, 100% humidity for 48 hours prior to mechanical tests. Data were statistically analyzed (ANOVA, Bonferroni tests, α = 0.05). Fractured specimens were examined under scanning electron microscopy (SEM), and FEA modeling of the crowns was performed. Mean FR values (N) were significantly higher with L (6102 ± 1519) and P (4117 ± 1083) than with of OCF (1900 ± 254) (p = 0.01). The mean SBS (MPa) in OCF (24 ± 4) was significantly lower (p 0.05). For crown restorations, while only adhesive failures were found in OCF, cohesive failures within veneering ceramic were more frequent in P and L. FEA verified these findings. Veneering methods based on layering or pressing may reduce ceramic chipping but the overcemented file-splitting method does not seem to prevent this failure. Layering and overpressing veneering methods on zirconia frameworks with reduced design might decrease chipping

  8. Temperature Dependence of Electrical Resistance of Woven Melt-Infiltrated SiCf/SiC Ceramic Matrix Composites

    Science.gov (United States)

    Appleby, Matthew P.; Morscher, Gregory N.; Zhu, Dongming

    2016-01-01

    Recent studies have successfully shown the use of electrical resistance (ER)measurements to monitor room temperature damage accumulation in SiC fiber reinforced SiC matrix composites (SiCf/SiC) Ceramic Matrix Composites (CMCs). In order to determine the feasibility of resistance monitoring at elevated temperatures, the present work investigates the temperature dependent electrical response of various MI (Melt Infiltrated)-CVI (Chemical Vapor Infiltrated) SiC/SiC composites containing Hi-Nicalon Type S, Tyranno ZMI and SA reinforcing fibers. Test were conducted using a commercially available isothermal testing apparatus as well as a novel, laser-based heating approach developed to more accurately simulate thermomechanical testing of CMCs. Secondly, a post-test inspection technique is demonstrated to show the effect of high-temperature exposure on electrical properties. Analysis was performed to determine the respective contribution of the fiber and matrix to the overall composite conductivity at elevated temperatures. It was concluded that because the silicon-rich matrix material dominates the electrical response at high temperature, ER monitoring would continue to be a feasible method for monitoring stress dependent matrix cracking of melt-infiltrated SiC/SiC composites under high temperature mechanical testing conditions. Finally, the effect of thermal gradients generated during localized heating of tensile coupons on overall electrical response of the composite is determined.

  9. Development of an oxidation resistant glass-ceramic composite coating on Ti-47Al-2Cr-2Nb alloy

    Science.gov (United States)

    Li, Wenbo; Zhu, Shenglong; Chen, Minghui; Wang, Cheng; Wang, Fuhui

    2014-02-01

    Three glass-ceramic composite coatings were prepared on Ti-47Al-2Cr-2Nb alloy by air spraying technique and subsequent firing. The aim of this work is to study the reactions between glass matrix and inclusions and their effects on the oxidation resistance of the glass-ceramic composite coating. The powders of alumina, quartz, or both were added into the aqueous solution of potassium silicate (ASPS) to form slurries used as the starting materials for the composite coatings. The coating formed from an ASPS-alumina slurry was porous, because the reaction between alumina and potassium silicate glass resulted in the formation of leucite (KAlSi2O6), consuming substantive glass phase and hindering the densification of the composite coating. Cracks were observed in the coating prepared from an ASPS-quartz slurry due to the larger volume shrinkage of the coating than that of the alloy. In contrast, an intact and dense SiO2-Al2O3-glass coating was successfully prepared from an ASPS-alumina-silica slurry. The oxidation behavior of the SiO2-Al2O3-glass composite coating on Ti-47Al-2Cr-2Nb alloy was studied at 900 °C. The SiO2-Al2O3-glass composite coating acted as an oxygen diffusion barrier, and prevented the inward diffusion of the oxygen from the air to the coating/alloy interface, therefore, decreasing the oxidation rate of the Ti-47Al-2Cr-2Nb alloy significantly.

  10. Comparative Evaluation of Friction Resistance of Titanium, Stainless Steel, Ceramic and Ceramic with Metal Insert Brackets with Varying Dimensions of Stainless Steel Wire: An In vitro Multi-center Study.

    Science.gov (United States)

    Kumar, B Sunil; Miryala, Suresh; Kumar, K Kiran; Shameem, K; Regalla, Ravindra Reddy

    2014-09-01

    The orthodontist seeks an archwire-bracket combination that has both good biocompatibility and low friction. Hence, the aim of this multicenter in vitro study was to evaluate and compare the frictional resistance generated between titanium (Ti), stainless steel (SS), ceramic and ceramic with metal insert (CMI) brackets with SS wires of varying dimensions in a specially designed apparatus. The material used in this study were Ti, SS, Ceramic and CMI with 0.018″ slot manufactured with zero degree tip and -7° torque premolar brackets (3M, Unitek) and SS wires of varying dimensions (0.016″ round, 0.016 × 0.016″ square, 0.016 × 0.022″ rectangular and 0.017 × 0.025″ rectangular) used. The frictional resistance was measured using Instron Universal testing machine (Model no. 4301). The specimen population in each center composed each of 160 brackets and wires. Differences among the all bracket/wire combinations were tested using (one-way) ANOVA, followed by the student Newman Keuls multiple comparisons of means ranking (at P frictional resistance. Ti brackets have least resistance and rectangular wires produced significant force. These can be used to avoid hazards of Nickel. SS brackets revealed higher static frictional force values as the wire dimension increased and showed lower static friction than Ti brackets for all wires except the thicker wire. Our study recommends the preclusion of brackets with rough surface texture (Ti brackets) with SS ligature wire for ligating bracket and archwire are better to reduce friction.

  11. Structure, mechanical and thermal behaviour of mixtures of polyester resin and dental ceramic waste

    Science.gov (United States)

    Peña Rodríguez, G.; Martínez Maldonado, L.; Dulce Moreno, H. J.

    2016-02-01

    The tensile strength and bending strength, structure and thermal behaviour of mixtures of polyester resin (P-2000) and powders (ASTM sieve 200, dental ceramic wastes (dentals impressions, alginate and gypsum) was reported. The samples consisted of mixtures with percentage weights of 50-50%, 60-40%, 70-30%, 80-20%, 90-10%, where the resin was the majority phase, the Mekc (4% wt) was used as catalyst. The structure was studied using SEM and XRD, the thermal behaviour using DSC, TGA and DMA, while the mechanical strength was tested using standards ASTM D790 and D638. Irregular morphology and presence of small agglomerations was observed, with particle sizes between 29.63 and 38.67μm, the presence of different phases of calcium sulphate was found, and that to the increasing the concentration of the powder, the materials becomes more crystalline, increasing its density. An average service temperature of 69.15±4.60°C was found. Vickers hardness values are reported in ranges from 18.65 to 27.96. Considering the elastic modules was established that the materials become more rigid by having more powder concentration.

  12. EFFECT OF Na₂B₄O₇ ADDITION ON THE STRUCTURE AND PROPERTIES OF Al₂O₃ CERAMIC-LINED STEEL PIPE PREPARED BY THE GS-SHS METHOD

    Directory of Open Access Journals (Sweden)

    Xinghui Hou

    2017-12-01

    Full Text Available By adding Na₂B₄O₇ into the Al-Fe₂O₃-Cr₂O₃ reaction system, the Al₂O₃ ceramic-lined steel pipe was prepared with the gravitational separation SHS method, and the influence of the Na₂B₄O₇ addition on the structure and properties of the produced composite steel pipe was investigated. The obtained results showed that the phase composition of the ceramic coating was Al₂O₃-FeCr Alloy-(Al0.9Cr0.1₂O₃ composite, and with the increase of the amount of Na₂B₄O₇ addition, the Fe-Cr alloy particles left in the ceramic coating increased and distributed uniformly, and the denser ceramic coating was obtained. However, when the amount of Na₂B₄O₇ addition increased further to over 4%, the ceramic coating became fractures, the hardness of ceramic coating decreased. The transition structure of steel pipe-transition layer-ceramic coating was formed, the thickness of the transition layer decreased with the addition of Na₂B₄O₇, and the boundaries between the transition layer and the ceramic layer were less obvious, which would have a significant effect on the improvement of the bonding quality of the composite steel pipe.

  13. 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.

  14. Effect on in vitro fracture resistance of the technique used to attach lithium disilicate ceramic veneer to zirconia frameworks.

    Science.gov (United States)

    Schmitter, M; Schweiger, M; Mueller, D; Rues, S

    2014-02-01

    This in vitro study should assess the fracture resistance of veneered zirconia-based crowns with either luted or fused veneer. Thirty-two identical zirconia frameworks (IPS e.max ZirCAD; Ivoclar/Vivadent), were constructed (inLab 3.80; Sirona Dental Systems). All frameworks were veneered with CAD/CAM-fabricated lithium disilicate ceramic (IPS e.max CAD; Ivoclar/Vivadent). For half the crowns (n=16) the veneer was luted to the framework (Multilink Implant; Ivoclar/Vivadent); for the other it was fused (IPS e.max Crystall./Connect; Ivoclar/Vivadent). Half of the specimens were then loaded until failure without artificial aging; the other half underwent artificial aging before assessment of the ultimate load. To compare the two techniques further, finite element analysis (FEA) and fractographic assessment using SEM and EDX analysis were conducted. Statistical assessment was performed by use of non-parametric tests. Initial fracture forces were higher in the fusion group (mean: 1388±190 N versus 1211±158 N). All specimens were insensitive to artificial aging. FEA showed that tensile stresses in the veneer at the frame-veneer interface were much higher for crowns with luted veneer; this may be the reason for their lower fracture resistance. Fractographic analysis revealed that both fused and luted specimens had cohesive and adhesive fracture patterns which resulted in partial delamination of the veneer. Fused crowns are superior to luted crowns. Comparison of fracture resistance with the maximum loads which may occur clinically (Fmax=600 N on one tooth) suggests both techniques might be used clinically, however. Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  15. Comparison of fracture resistance and fracture characterization of bilayered zirconia/fluorapatite and monolithic lithium disilicate all ceramic crowns.

    Science.gov (United States)

    Altamimi, Abdulaziz M; Tripodakis, Aris Petros; Eliades, George; Hirayama, Hiroshi

    2014-01-01

    To compare the fracture resistance between bilayered zirconia/ fluorapatite and monolithic lithium disilicate heat-pressed crowns and characterize the mode of fracture failure. Thirty crown samples were sequentially fitted on a mandibular right first molar metal replica of an ivory prepared molar tooth. The crown specimens were divided in three groups (A, B, and C; n = 10 for each group). Group A consisted of bilayered zirconia/fluorhapatite pressed-over crowns with standard design crown copings (0.7 mm uniform thickness), Group B of bilayered zirconia/fluorhapatite with anatomical design crown copings, and Group C of lithium disilicate monolithic crowns. The samples were then dynamically loaded under water for 100,000 cycles with a profile of 250 N maximum load at 1,000 N/s rate and 2.0 Hz frequency. Loading was performed with a steel ball (5 mm in diameter) coming into contact with the test crown, loading to maximum, holding for 0.2 s, unloading and lifting off 0.5 mm. The samples were then fractured under static loading, in order to determine the ultimate crown strength. Analysis of the recorded fracture load values was carried out with one-way analysis of variance (ANOVA) followed by Tukey tests. Fractured specimens were examined by stereomicroscopy and scanning electron microscopy. The fracture loads measured were (N, means and standard deviations): Group A: 561.87 (72.63), Group B: 1,014.16 (70.18) and Group C: 1,360.63 (77.95). All mean differences were statistically significant (P crowns showed more fracture resistance than zirconia/fluorapatite pressed-over crowns. Within the bilayered groups, the anatomical zirconia coping design presented increased ceramic fracture resistance.

  16. Mechanical properties of ceramic structures based on Triply Periodic Minimal Surface (TPMS) processed by 3D printing

    Science.gov (United States)

    Restrepo, S.; Ocampo, S.; Ramírez, J. A.; Paucar, C.; García, C.

    2017-12-01

    Repairing tissues and organs has been the main goal of surgical procedures. Since the 1990s, the main goal of tissue engineering has been reparation, using porous scaffolds that serve as a three-dimensional template for the initial fixation of cells and subsequent tissue formation both in vitro and in vivo. A scaffold must have specific characteristics of porosity, interconnectivity, surface area, pore volume, surface tortuosity, permeability and mechanical properties, which makes its design, manufacturing and characterization a complex process. Inspired by nature, triply periodic minimal surfaces (TPMS) have emerged as an alternative for the manufacture of porous pieces with design requirements, such as scaffolds for tissue repair. In the present work, we used the technique of 3D printing to obtain ceramic structures with Gyroid, Schwarz Primitive and Schwarz Diamond Surfaces shapes, three TPMS that fulfil the geometric requirements of a bone tissue scaffold. The main objective of this work is to compare the mechanical properties of ceramic pieces of three different forms of TPMS printed in 3D using a commercial ceramic paste. In this way it will be possible to clarify which is the TPMS with appropriate characteristics to construct scaffolds of ceramic materials for bone repair. A dependence of the mechanical properties with the geometry was found being the Primitive Surface which shows the highest mechanical properties.

  17. Air void structure and frost resistance

    DEFF Research Database (Denmark)

    Hasholt, Marianne Tange

    2014-01-01

    This article compiles results from 4 independent laboratory studies. In each study, the same type of concrete is tested at least 10 times, the air void structure being the only variable. For each concrete mix both air void analysis of the hardened concrete and a salt frost scaling test are conduc......This article compiles results from 4 independent laboratory studies. In each study, the same type of concrete is tested at least 10 times, the air void structure being the only variable. For each concrete mix both air void analysis of the hardened concrete and a salt frost scaling test...... is proportional to the product of total air content and specific surface. In all 4 cases, the conclusion is concurrent that the parameter of total surface area of air voids performs equally well or better than the spacing factor when linking air void characteristics to frost resistance (salt frost scaling......). This observation is interesting as the parameter of total surface area of air voids normally is not included in air void analysis. The following reason for the finding is suggested: In the air voids conditions are favourable for ice nucleation. When a capillary pore is connected to an air void, ice formation...

  18. Laser cladding of high performance ceramic sheets on a low quality ceramic substrate

    International Nuclear Information System (INIS)

    Triantafyllidis, D.; Li, L.; Stott, F.H.

    2004-01-01

    High alumina refractory ceramics offer increased resistance in slagging environments. In particular, the presence of more than 5% Cr 2 O 3 in a high alumina refractory ceramic increases its slag corrosion resistance due to the formation of a dense Cr-spinel oxide layer at the refractory/slag interface. However, refractory ceramics containing more that 5% Cr 2 O 3 cost significantly more than Cr 2 O 3 -free refractory ceramics. The surface and near-surface compositions and properties are more important than the bulk properties for high-temperature applications in slag-containing environments. Laser cladding, therefore, is a useful tool for developing refractory ceramics with a low-cost substrate and a high slag-corrosion resistant surface layer. This paper presents a technique involving cladding of pre-positioned layers of a 85% Al 2 O 3 -5% Cr 2 O 3 ceramic on a 60% Al 2 O 3 refractory ceramic, focusing on the process characteristics. A simple model that describes the process of multi-sheet cladding is developed and the operating map for the process is presented. The microstructural characteristics of the clad surfaces have been analysed by optical and scanning electron microscopy (SEM), as well as energy dispersion X-ray spectroscopy (EDX), revealing the formation of an intermediate layer between the substrate and the top ceramic sheets in multi-sheet cladding. A bi-phasic structure is formed in the clad surface, comprising of an Al 2 O 3 -Cr 2 O 3 -based solid solution and a SiO 2 -based matrix

  19. Proceedings of the national symposium on materials and processing: functional glass/glass-ceramics, advanced ceramics and high temperature materials

    International Nuclear Information System (INIS)

    Ghosh, A.; Sahu, A.K.; Viswanadham, C.S.; Ramanathan, S.; Hubli, R.C.; Kothiyal, G.P.

    2012-10-01

    With the development of materials science it is becoming increasingly important to process some novel materials in the area of glass, advanced ceramics and high temperature metals/alloys, which play an important role in the realization of many new technologies. Such applications demand materials with tailored specifications. Glasses and glass-ceramics find exotic applications in areas like radioactive waste storage, optical communication, zero thermal expansion coefficient telescopic mirrors, human safety gadgets (radiation resistance windows, bullet proof apparels, heat resistance components etc), biomedical (implants, hyperthermia treatment, bone cement, bone grafting etc). Advanced ceramic materials have been beneficial in biomedical applications due to their strength, biocompatibility and wear resistance. Non-oxide ceramics such as carbides, borides, silicides, their composites, refractory metals and alloys are useful as structural and control rod components in high temperature fission/ fusion reactors. Over the years a number of novel processing techniques like selective laser melting, microwave heating, nano-ceramic processing etc have emerged. A detailed understanding of the various aspects of synthesis, processing and characterization of these materials provides the base for development of novel technologies for different applications. Keeping this in mind and realizing the need for taking stock of such developments a National Symposium on Materials and Processing -2012 (MAP-2012) was planned. The topics covered in the symposium are ceramics, glass/glass-ceramics and metals and materials. Papers relevant to INIS are indexed separately

  20. Effect of different surface treatments on bond strength, surface and microscopic structure of zirconia ceramic

    Directory of Open Access Journals (Sweden)

    Zeinab R. El-Shrkawy

    2016-06-01

    Conclusions: (1 Surface treatments of Y-TZP ceramic together with MDP primer and silane-coupling agent application improve the bond strength to resin cement. (2 Plasma-Silica coating and plasma-oxygen treatment, both are valuable methods that improve the bond strength of resin cement to Y-TZP ceramic. (3 Silica coating by plasma technology provides durable bond strength and can be a promising alternative pretreatment before silane application to enhance bonding with zirconia ceramic. (4 Tetragonal-monoclinic phase transformation had occurred in Y-TZP samples received both types of plasma treatment.

  1. DEVELOPMENT OF WEAR RESISTANT COATINGS FORMED BY PLASMA SPRAYING OF ALLOY Ni–Fe–Cr–Si–B–C SYSTEM REINFORCED WITH CERAMICS Al2O3

    Directory of Open Access Journals (Sweden)

    A. S. Kalinichenko

    2016-01-01

    Full Text Available . Creating a functionally oriented, including nanostructured, anti-friction materials and coatings with qualitatively new complex of service properties is an important scientific and practical problem. In particular, for the cable industry it is urgent task of ensuring the high performance properties of fast deteriorating stretching and supporting rollers. Working surfaces of these parts operate under practically dry friction conditions with constantly updated material of stretching wire. Plasma spraying is one of the widely used methods of surface engineering to create wear resistant coatings and which is characterized with process flexibility and the ability to create coatings using various materials and alloys including composite ones. The installation UPU-3D with the PP-25 plasma torch was used for plasma spraying. The thickness of the sprayed layer was 0.8–1.1 mm. As a material for the deposition of composite coatings a powder mixture of self-fluxing nickel alloy PG-HN80SR4 (system Ni–Fe–Cr–Si–B–C and a neutral oxide ceramics Al2O3 was used. The amount of ceramics varied from 15 to 33 %. This ceramic oxide was selected due to the desire to reduce coatings’ costs while providing high durability. Carried out phase and microstructural studies have shown when ceramics was added in an amount more than 20 % a formation of conglomerates formed by not melted alumina particles often was observed. These conglomerates serve as crack formation centers in the coating. The phase composition of the coatings practically does not depend on the content of ceramics compounds. Tribological tests have shown that the best results were obtained when the content of the oxide ceramic in the coating was in the range from 15 to 20 %.

  2. Fracture resistance of crowns cemented on titanium and zirconia implant abutments: a comparison of monolithic versus manually veneered all-ceramic systems.

    Science.gov (United States)

    Martínez-Rus, Francisco; Ferreiroa, Alberto; Özcan, Mutlu; Bartolomé, José F; Pradíes, Guillermo

    2012-01-01

    To evaluate the fracture resistance of all-ceramic crowns cemented on titanium and zirconia implant abutments. Customized implant abutments for maxillary right central incisors made of titanium (Ti) and zirconia (Zr) (n=60, n=30 per group) were fabricated for an internal connection implant system. All-ceramic crowns were fabricated for their corresponding implant abutments using the following systems (n=10 per group): (1) monolithic computer-aided design/computer-assisted manufacture (CAD/CAM) lithium disilicate (MLD); (2) pressed lithium disilicate (PLD); (3) yttrium stabilized tetragonal zirconia polycrystal (YTZP). The frameworks of both PLD and YTZP systems were manually veneered with a fluorapatite-based ceramic. The crowns were adhesively cemented to their implant abutments and loaded to fracture in a universal testing machine (0.5 mm/minute). Data were analyzed using two-way analysis of variance (ANOVA) and Tukey's test (α=0.05). Both the abutment material (P=.0001) and the ceramic crown system (P=.028) significantly affected the results. Interaction terms were not significant (P=.598). Ti-MLD (558.5±35 N) showed the highest mean fracture resistance among all abutment-crown combinations (340.3±62-495.9±53 N) (Pcrown system showed significantly higher mean fracture resistance compared to manually veneered ones on both Ti and Zr abutments (Pcrown combinations failed only in the crowns without abutment fractures, Zr-YTZP combination failed exclusively in the abutment without crown fracture. Zr-MLD and Zr-PLD failed predominantly in both the abutment and the crown. Ti-YTZP showed only implant neck distortion. The highest fracture resistance was obtained with titanium abutments restored with MLD crowns, but the failure type was more favorable with Ti-YTZP combination.

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

    Directory of Open Access Journals (Sweden)

    Myung-Jin Lim

    2017-02-01

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

  4. Portfolio: Ceramics.

    Science.gov (United States)

    Hardy, Jane; And Others

    1982-01-01

    Describes eight art activities using ceramics. Elementary students created ceramic tiles to depict ancient Egyptian and medieval European art, made ceramic cookie stamps, traced bisque plates on sketch paper, constructed clay room-tableaus, and designed clay relief masks. Secondary students pit-fired ceramic pots and designed ceramic Victorian…

  5. Final Regulations to Reduce Toxic Air Pollutant Emissions from Brick and Structural Clay Products Manufacturing and Clay Ceramics Manufacturing Fact Sheets

    Science.gov (United States)

    This page contains a February 2003 and September 2015 fact sheet with information regarding the final rules to the NESHAP for Brick and Structural Clay Products Manufacturing and the NESHAP for Clay Ceramics Manufacturing

  6. Separation of Mercury Resistant Bacteria from Wastewater of Milk, Detergent and Ceramic Industry

    Directory of Open Access Journals (Sweden)

    M. Moghbeli , F. Shakeri and H. Hashemi-Moghaddam

    2011-09-01

    Full Text Available Use of microorganisms for removing mercury is an effective technology for the treatment of industrial wastewaters and can become an effective tool for the remediation of man-impacted coastal ecosystems with this metal. In this study, seven types of mercury resistant bacteria were separated from industrial waste and minimum inhibitory concentration (MIC, were determined for these bacteria. Results showed that two strains of bacteria, which isolated from waste water detergent plants, are more resistant to mercury and able to grow at the presence of 52 ppm of mercuric chloride. These bacteria could be used for biological treatment of mercury in contaminated wastewater.

  7. Fracture Resistance of Molar Crowns Fabricated with Monolithic All-Ceramic CAD/CAM Materials Cemented on Titanium Abutments: An In Vitro Study.

    Science.gov (United States)

    Dogan, Derya Ozdemir; Gorler, Oguzhan; Mutaf, Burcu; Ozcan, Mutlu; Eyuboglu, Gunes Bulut; Ulgey, Melih

    2017-06-01

    To assess the fracture resistance of single-tooth implant-supported crown restorations made with different CAD/CAM blocks. Thirty-six titanium abutments were put on dental implant analogs (Mis Implant). For each of three test groups (n = 12/group), implant-supported, cement-retained mandibular molar single crowns were produced. Crowns were made of lithium disilicate glass (LD) IPS e.max CAD, feldspathic glass ceramic (FEL) Vita Mark II, and resin nano-ceramic (RNC) Lava Ultimate. The crowns were cemented with self-adhesive resin cement RelyX Unicem 2. After chewing cycling, crowns were tested to failure in a universal testing machine. Fracture values were calculated as initial (F-initial) and maximum fracture (F-max). The study groups were ranked, in order of having highest value, (LD > FEL) > RNC for F-initial load value and (LD > RNC) > FEL for F-max load value. This demonstrated that there was no parallel change in the F-initial and F-max values presenting the fracture resistance of specimens. There was no accordance between the F-initial and F-max values of the LD, RNC, and FEL after chewing simulation with thermocycling resembling 5 years of clinical functional use. LD had the highest fracture resistance during the fracture test. RNC had low fracture resistance; however, it had considerably high fracture resistance during the fracture test. FEL had considerably low fracture resistance values. © 2015 by the American College of Prosthodontists.

  8. Structural and optical properties of Tb-doped Na-Gd metaphosphate glasses and glass-ceramics

    Czech Academy of Sciences Publication Activity Database

    Moretti, F.; Vedda, A.; Nikl, Martin; Nitsch, Karel

    2009-01-01

    Roč. 21, č. 15 (2009), 155103/1-155103/7 ISSN 0953-8984 R&D Projects: GA AV ČR IAA200100626 Institutional research plan: CEZ:AV0Z10100521 Keywords : Na-Gd metaphosphate glass * glass -ceramics * NaGd(PO 3 ) 4 * optical properties * structural properties * Raman spectroscopy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.964, year: 2009

  9. Structural and Magnetic Characterizations of Nano Sized Grain Zinc Ferrite/Hydroxyapatite Ceramic Prepared by Solid State Reaction Route.

    Science.gov (United States)

    Pankaew, Piyapong; Klumdoung, Pattarinee

    2015-11-01

    A promising composite of bioactive hydroxyapatite (HAp) and zinc ferrite (ZnFe2O4) has potentials for future bone reinforcing formation. In present study, HAp and ZnFe2O4 composite ceramic was prepared by solid state reaction route for easier control of structural and magnetic characteristics and with low cost. HAp powder was synthesized by precipitation method from chicken eggshell. Mixed powders with varying ZnFe2O4/HAp weight ratios from 2-10 wt% were milled together and uniaxially pressed and then sintered at 1200 degrees C for 3 hours. The XRD results showing no other phases of composite ceramics with only HAp and ZnFe2O4 phases were identified, indicating high stability of HAp property. Phase fractions of ZnFe2O4 were found to increase from 10.8 to 18.73 wt% with increasing content of ZnFe2O4. FT-IR results were only revealed vibration bands of standard HAp phase. SEM results revealed primary grains sizes of the prepared ceramics in nano scale. The BET surface area and pore volume increased with increasing content of ZnFe2O4 in composite ceramics. The VSM results of composites with increasing ZnFe2O4 content had been shown with increasing magnetization from 0.05 to 1.85 emu/g while their coercivities were decreased from 44 to 24 Oe. Higher magnetization as well as higher super paramagnetic behavior could be achieved with increasing the studied ZnFe2O4 weight ratios in ZnFe2O4/HAp composite ceramics, which can be tailored for specific applications.

  10. Ceramic Composite Mechanical Fastener System for High-Temperature Structural Assemblies, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — Under Phase I, the feasibility of a novel thermal stress-free ceramic composite mechanical fastener system suitable for assembly of high-temperature composite...

  11. Influence of niobium substitution on structural and opto-electrical properties of BNKT piezoelectric ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Chauhan, Vidhi [Electroceramics Research Group, Department of Physics, Birla Institute of Technology, Mesra, Ranchi (India); Ghosh, S.K., E-mail: saritghosh@gmail.com [Electroceramics Research Group, Department of Physics, Birla Institute of Technology, Mesra, Ranchi (India); Hussain, Ali [School of Advanced Materials Engineering, Changwon National University, Gyeong-Nam, 641-773 (Korea, Republic of); Rout, S.K., E-mail: skrout@bitmesra.ac.in [Electroceramics Research Group, Department of Physics, Birla Institute of Technology, Mesra, Ranchi (India)

    2016-07-25

    Lead free niobium modified piezoelectric ceramics Bi{sub 0.5}Na{sub 0.25}K{sub 0.25}Nb{sub x}Ti{sub 1-x}O{sub 3} (BNKT) (x = 0.0, 0.015 and 0.025) compositions along with their structural and opto-electrical properties are investigated. At room temperature Rietveld refinement analysis on x-ray diffraction data revealed the evidence of tetragonal (P4mm) + cubic (Pm3m) mixed phases at 0.015Nb-BNKT composition and at higher niobium concentration it moves towards cubic phase. Presence of local disorder controls the Raman active vibrational modes along with excitation and emission spectra in these materials. The temperature dependence dielectric constant is investigated in the frequency range of 1 kHz–100 kHz. The broadening of dielectric peak and frequency dependence behavior indicated a relaxor property in these materials. Induced A-site vacancies and coexistence of tetragonal-pseudocubic phases lower the depolarization temperature (T{sub d}) with niobium concentration. The structural mix phases have been correlated with the piezoelectric coefficients and the composition x = 0.015 depicts the better piezoelectric properties amongst the studied compositions which is endorsed to the mixed symmetry of tetragonal and cubic phases. - Highlights: • Coexistence of polar and non-polar phases in Nb doped BNKT materials. • Structural instability and lattice disorder controls the opto-electrical properties. • Broadening and shifting of dielectric peaks highlighted the relaxor behavior. • High value of ferroelectric and piezoelectric coefficients at x = 0.015 composition.

  12. Investigation into the morphology, composition, structure and dry tribological behavior of rice husk ceramic particles

    Science.gov (United States)

    Hu, Enzhu; Hu, Kunhong; Xu, Zeyin; Hu, Xianguo; Dearn, Karl David; Xu, Yong; Xu, Yufu; Xu, Le

    2016-03-01

    To expand the application of rice husk (RH) resource, this study developed carbon-based RH ceramic (RHC) particles using a common high-temperature carbonization method. The morphology, composition, and structure of the RHC particles were characterized with a series of modern analysis technologies and were then compared with those of the initial RH powder and carbonized RH (CRH) particles. The dry tribological behavior of RHC particle adobes (RHAs) was also investigated. Results showed the sheet-shaped morphology of the RHC particles. The graphitization degree of the RHC particles was lower than that of the CRH particles possibly because the phenolic resin (PR) filled the micro-pores of the RH particles, thereby prompting the formation of amorphous carbon in the RHC particles as a result of high-temperature carbonization. The appearance of a hydroxy function group (sbnd OH) on the surface of the RHC particles was ascribed to the decomposition of PR at 900 °C. The friction coefficients and mass loss rates of the RHAs almost increased with the rise in load and velocity. In addition, the friction coefficients of the RHAs decreased at high load (5 N) and velocity (0.261 m/s) conditions. Such outcome indicated that the variation of contact area between steel ball and RHA at high load and velocity conditions resulted in the abrasive wear or catastrophic wear.

  13. Rare earth-doped lead borate glasses and transparent glass-ceramics: structure-property relationship.

    Science.gov (United States)

    Pisarski, W A; Pisarska, J; Mączka, M; Lisiecki, R; Grobelny, Ł; Goryczka, T; Dominiak-Dzik, G; Ryba-Romanowski, W

    2011-08-15

    Correlation between structure and optical properties of rare earth ions in lead borate glasses and glass-ceramics was evidenced by X-ray-diffraction, Raman, FT-IR and luminescence spectroscopy. The rare earths were limited to Eu(3+) and Er(3+) ions. The observed BO(3)↔BO(4) conversion strongly depends on the relative PbO/B(2)O(3) ratios in glass composition, giving important contribution to the luminescence intensities associated to (5)D(0)-(7)F(2) and (5)D(0)-(7)F(1) transitions of Eu(3+). The near-infrared luminescence and up-conversion spectra for Er(3+) ions in lead borate glasses before and after heat treatment were measured. The more intense and narrowing luminescence lines suggest partial incorporation of Er(3+) ions into the orthorhombic PbF(2) crystalline phase, which was identified using X-ray diffraction analysis. Copyright © 2010 Elsevier B.V. All rights reserved.

  14. A ceramic radial insulation structure for a relativistic electron beam vacuum diode.

    Science.gov (United States)

    Xun, Tao; Yang, Hanwu; Zhang, Jiande; Liu, Zhenxiang; Wang, Yong; Zhao, Yansong

    2008-06-01

    For one kind of a high current diode composed of a small disk-type alumina ceramic insulator water/vacuum interface, the insulation structure was designed and experimentally investigated. According to the theories of vacuum flashover and the rules for radial insulators, a "cone-column" anode outline and the cathode shielding rings were adopted. The electrostatic field along the insulator surface was obtained by finite element analysis simulating. By adjusting the outline of the anode and reshaping the shielding rings, the electric fields were well distributed and the field around the cathode triple junction was effectively controlled. Area weighted statistical method was applied to estimate the surface breakdown field. In addition, the operating process of an accelerator based on a spiral pulse forming line (PFL) was simulated through the PSPICE software to get the waveform of charging and diode voltage. The high voltage test was carried out on a water dielectric spiral PFL accelerator with long pulse duration, and results show that the diode can work stably in 420 kV, 200 ns conditions. The experimental results agree with the theoretical and simulated results.

  15. Effect of magnesium aluminum silicate glass on the thermal shock resistance of BN matrix composite ceramics

    NARCIS (Netherlands)

    Cai, Delong; Jia, Dechang; Yang, Zhihua; Zhu, Qishuai; Ocelik, Vaclav; Vainchtein, Ilia D.; De Hosson, Jeff Th M.; Zhou, Yu

    The effects of magnesium aluminum silicate (MAS) glass on the thermal shock resistance and the oxidation behavior of h-BN matrix composites were systematically investigated at temperature differences from 600 degrees C up to 1400 degrees C. The retained strength rate of the composites rose with the

  16. A new high temperature resistant glass–ceramic coating for gas ...

    Indian Academy of Sciences (India)

    Unknown

    corrosion resistance characteristics. In modern gas turbine engines, critical material failures and deterioration problems result from chemical attack, thermal shock, erosion and differences in thermal expan- sion coefficients. There are five basic reasons, as given here, for using coatings at high temperature (Huminik 1963):.

  17. Microstructure and mechanical properties of silicon nitride structural ceramics of silicon nitride

    International Nuclear Information System (INIS)

    Strohaecker, T.R.; Nobrega, M.C.S.

    1989-01-01

    The utilization of direct evaluation technic of tenacity for fracturing by hardness impact in silicon nitride ceramics is described. The microstructure were analysied, by Scanning Electron Microscopy, equiped with a microanalysis acessory by X ray energy dispersion. The difference between the values of K IC measure for two silicon nitride ceramics is discussed, in function of the microstructures and the fracture surfaces of the samples studied. (C.G.C.) [pt

  18. Silicon nitride: A ceramic material with outstanding resistance to thermal shock and corrosion

    Science.gov (United States)

    Huebner, K. H.; Saure, F.

    1983-01-01

    The known physical, mechanical and chemical properties of reaction-sintered silicon nitride are summarized. This material deserves interest especially because of its unusually good resistance to thermal shock and corrosion at high temperatures. Two types are distinguished: reaction-sintered (porous) and hot-pressed (dense) Si3N4. Only the reaction-sintered material which is being produced today in large scale as crucibles, pipes, nozzles and tiles is considered.

  19. Effect of different ferrule designs on the fracture resistance and failure pattern of endodontically treated teeth restored with fiber posts and all-ceramic crowns

    Directory of Open Access Journals (Sweden)

    Haneef Sherfudhin

    2011-02-01

    Full Text Available OBJECTIVE: This study investigated the effect of different ferrule heights on endodontically treated premolars. MATERIAL AND METHODS: Fifty sound mandibular first premolars were endodontically treated and then restored with 7-mm fiber post (FRC Postec Plus #1 Ivoclar-Vivadent luted with self-polymerized resin cement (Multilink, Ivoclar Vivadent while the coronal section was restored with hybrid composite core build-up material (Tetric Ceram, Ivoclar-Vivadent, which received all-ceramic crown. Different ferrule heights were investigated: 1-mm circumferential ferrule without post and core (group 1 used as control, a circumferential 1-mm ferrule (group 2, non-uniform ferrule 2-mm buccally and 1-mm lingually (group 3, non-uniform ferrule 3-mm buccally and 2-mm lingually (group 4, and finally no ferrule preparation (group 5. The fracture load and failure pattern of the tested groups were investigated by applying axial load to the ceramic crowns (n=10. Data were analyzed statistically by one-way ANOVA and Tukey's post-hoc test was used for pair-wise comparisons (α=0.05. RESULTS: There were no significant differences among the failure load of all tested groups (P<0.780. The control group had the lowest fracture resistance (891.43±202.22 N and the highest catastrophic failure rate (P<0.05. Compared to the control group, the use of fiber post reduced the percentage of catastrophic failure while increasing the ferrule height did not influence the fracture resistance of the restored specimens. CONCLUSIONS: Within the limitations of this study, increasing the ferrule length did not influence the fracture resistance of endodontically treated teeth restored with glass ceramic crowns. Insertion of a fiber post could reduce the percentage of catastrophic failure of these restorations under function.

  20. Evaluation of the physicochemical properties of structured materials: metallic, polymeric and ceramic, for the treatment of sour gases; Evaluacion de las propiedades fisicoquimicas de materiales estructurados: metalico, polimerico y ceramico, para el tratamiento de gases acidos

    Energy Technology Data Exchange (ETDEWEB)

    Salazar, A.; Chavez, R. H. [ININ, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico); Olea, O.; Solis, D., E-mail: rosahilda.chavez@inin.gob.mx [Universidad Autonoma del Estado de Mexico, Facultad de Quimica, Cerro de Coatepec s/n, Ciudad Universitaria, 50100 Toluca, Estado de Mexico (Mexico)

    2013-07-01

    in this work the physicochemical properties of three structured materials: metallic, polymeric and ceramic, from Sulzer Brothers Limited brand, are studied in order to removal sour gases, by absorption process, in aqueous solution of Monoethanolamine (Mea), at 30% weight. Mechanical properties, chemical composition, morphology and corrosion resistance were determined, using different characterization techniques, such as: 1) mechanically, according to standard procedures Astm E-384-1990, 2) chemically, by the corrosion resistance in the presence of an electrochemical cell, in aqueous solution of H{sub 2}SO{sub 4}, 1 N by Astm G-5-1999, 3) morphologically by scanning electron microscopy technique, and 4) efficiency of separation, by the gas chromatography technique in order to determine the chemical absorption of CO{sub 2} by Mea. The ceramic material was the hardest with 700 Hk value and tensile strength of 90 MPa, likewise showed resistance to corrosion of 10.28 m py, separation efficiency of 74% CO{sub 2}, at 10 minutes. The metallic material had a hardness of 190 Hk and it was the most resistant of tension, with 831 MPa, and corrosion resistance of 780.4 x 10{sup -6} m py, likewise promoted CO{sub 2} separation efficiency of 90% during the evaluation. The polymeric material presented hardness of 20 Hk and 35 MPa and it was not suffered surface change with electrochemical attack, with 282.4 x 10{sup -6} m py, and separation efficiency of 88%. Therefore the polymer was the most ductile, with smooth surface and greater resistance with H{sub 2}SO{sub 4}. The metal material was more resistant to plastic deformation and more corrugated surface and the second resistance in the presence of acid medium in aqueous solutions. For all the above, the metallic material is recommended by its greater separation in the reduction of acid gases and the polymer due to its greater chemical resistance. (Author)

  1. Study of structural, electrical, and dielectric properties of phosphate-borate glasses and glass-ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Melo, B. M. G.; Graça, M. P. F., E-mail: mpfg@ua.pt; Prezas, P. R.; Valente, M. A. [Physics Department (I3N), Aveiro University, Campus Universitário de Santiago, Aveiro (Portugal); Almeida, A. F.; Freire, F. N. A. [Mechanics Engineering Department, Ceará Federal University, Fortaleza (Brazil); Bih, L. [Equipe Physico-Chimie la Matière Condensée, Faculté des Sciences de Meknès, Meknès (Morocco)

    2016-08-07

    In this work, phosphate-borate based glasses with molar composition 20.7P{sub 2}O{sub 5}–17.2Nb{sub 2}O{sub 5}–13.8WO{sub 3}–34.5A{sub 2}O–13.8B{sub 2}O{sub 3}, where A = Li, Na, and K, were prepared by the melt quenching technique. The as-prepared glasses were heat-treated in air at 800 °C for 4 h, which led to the formation of glass-ceramics. These high chemical and thermal stability glasses are good candidates for several applications such as fast ionic conductors, semiconductors, photonic materials, electrolytes, hermetic seals, rare-earth ion host solid lasers, and biomedical materials. The present work endorses the analysis of the electrical conductivity of the as-grown samples, and also the electrical, dielectric, and structural changes established by the heat-treatment process. The structure of the samples was analyzed using X-Ray powder Diffraction (XRD), Raman spectroscopy, and density measurements. Both XRD and Raman analysis confirmed crystals formation through the heat-treatment process. The electrical ac and dc conductivities, σ{sub ac} and σ{sub dc}, respectively, and impedance spectroscopy measurements as function of the temperature, varying from 200 to 380 K, were investigated for the as-grown and heat-treated samples. The impedance spectroscopy was measured in the frequency range of 100 Hz–1 MHz.

  2. Structure and short time degradation studies of sodium zirconium phosphate ceramics loaded with simulated fast breeder (FBR) waste

    Science.gov (United States)

    Ananthanarayanan, A.; Ambashta, R. D.; Sudarsan, V.; Ajithkumar, T.; Sen, D.; Mazumder, S.; Wattal, P. K.

    2017-04-01

    Sodium zirconium phosphate (NZP) ceramics have been prepared using conventional sintering and hot isostatic pressing (HIP) routes. The structure of NZP ceramics, prepared using the HIP route, has been compared with conventionally sintered NZP using a combination of X-ray diffraction (XRD) and (31P and 23Na) nuclear magnetic resonance (NMR) spectroscopy techniques. It is observed that NZP with no waste loading is aggressive toward the steel HIP-can during hot isostatic compaction and significant fraction of cations from the steel enter the ceramic material. Waste loaded NZP samples (10 wt% simulated FBR waste) show significantly low can-interaction and primary NZP phase is evident in this material. Upon exposure of can-interacted and waste loaded NZP to boiling water and steam, 31P NMR does not detect any major modifications in the network structure. However, the 23Na NMR spectra indicate migration of Na+ ions from the surface and possible re-crystallization. This is corroborated by Small-Angle Neutron Scattering (SANS) data and Scanning Electron Microscopy (SEM) measurements carried out on these samples.

  3. Evaluation of structure, dielectric and electrical properties of (Li/Ta/Sb modified (Na, K NbO3 lead-free ceramics with excess Na concentration

    Directory of Open Access Journals (Sweden)

    Md. Kashif Shamim

    2017-12-01

    Full Text Available Polycrystalline perovskite structured (Li0.04 (Na0.54+x K0.460.96 (Nb0.81Ta0.15 Sb0.04 O3 ceramics with x=0.00, 0.005 and 0.01 mole excess Na concentration were prepared by solid state sintering method. The present study relates the role of excess Na addition with the stoichiometry, density, structure, dielectric and ferroelectric properties of the samples. X-ray diffraction (XRD pattern exhibits single phase orthorhombic structure. The characteristic Raman modes were observed due to translational modes of cations and vibrational modes of NbO6 octahedra and no structural phase transition were observed. This confirms the formation of single phase perovskite structure and is consistent with XRD results. The dielectric permittivity increases about two times, while dielectric loss decreases by four times for x=0.01 composition. The electrical measurements carried by Complex Impedance spectroscopic analysis suggest negative temperature coefficient of resistance (NTCR behavior.

  4. Study of potentiality of raw material of Crato/CE for use in structural ceramics - part I - technological characterization

    International Nuclear Information System (INIS)

    Andrade, J.C.S.; Santos, G.M.; Saldanha, K.M.; Sales Junior, J.C.C.; Nascimento, R.M.; Paskocimas, C.A.

    2011-01-01

    The limitation of information on chemical, mineralogical and thermal characteristics of raw material used in process of manufacture of ceramic products in the region of Cariri, specifically the city of Crato, state of Ceara, motivated the development of this work, since this region ceramics exist that in a general context they appear as important productive chains in the state. The characteristics were evaluated by tests of limit of liquidity, limit of plasticity, index of plasticity, but also by chemical analysis for fluorescence of rays X, analysis of phases for diffraction of rays X, and thermal analysis (thermogratimetric analysis). The results showed that the raw material has excellent size distribution and characteristics acceptable to the processing of structural components of dark color the red, requiring a mixture of clay with coarse less plastic which granulation, that functions as reducer of plasticity. (author)

  5. Preparation of glasses and glass ceramics of heavy metal oxides containing silver: optical, structural and electrochemical properties

    International Nuclear Information System (INIS)

    Bregadiolli, Bruna A.; Souza, Ernesto R.; Sigoli, Fernando A.; Caiut, Jose M.A.; Alencar, Monica A.S.; Benedetti, Assis V.; Nalin, Marcelo

    2012-01-01

    Silver containing heavy metal oxide glasses and glass ceramics of the system WO 3 -SbPO 4 -PbO-AgCl with different AgCl contents have been prepared and their thermal, structural and optical properties characterized. Glass ceramics containing metallic silver nanoparticles have been prepared by annealing glass samples at temperatures above the glass transition and analyzed by transmission electron microscopy and energy dispersive X-ray microanalysis. The presence of the metallic clusters has been also confirmed by the observation of a surface plasmon resonance band in the visible range. Cyclic voltammetric measurements indicated the presence of metallic silver into the glasses, even before to perform the thermal treatment. (author)

  6. Preparation of glasses and glass ceramics of heavy metal oxides containing silver: optical, structural and electrochemical properties

    Directory of Open Access Journals (Sweden)

    Bruna A. Bregadiolli

    2012-01-01

    Full Text Available Silver containing heavy metal oxide glasses and glass ceramics of the system WO3-SbPO4-PbO-AgCl with different AgCl contents have been prepared and their thermal, structural and optical properties characterized. Glass ceramics containing metallic silver nanoparticles have been prepared by annealing glass samples at temperatures above the glass transition and analyzed by transmission electron microscopy and energy dispersive X-ray microanalysis. The presence of the metallic clusters has been also confirmed by the observation of a surface plasmon resonance band in the visible range. Cyclic voltammetric measurements indicated the presence of metallic silver into the glasses, even before to perform the thermal treatment.

  7. Doping and defect structure of mixed-conducting ceramics for gas separation

    Science.gov (United States)

    Zuo, Chendong

    A worldwide energy crisis and increasing environmental concerns are strong incentives for using hydrogen as a sustainable and clean energy source. "Hydrogen economy" has been around since 1970s, but it started to look practicable only in recent years. The trend in the future is to switch from using hydrogen as the basic raw material in the chemical industry to the energy carrier in the transportation and distributed energy industries. To meet the expected rising demand, hydrogen has to be generated in a more cost-effective manner. As one of the most important operation units in the hydrogen production, a high performance hydrogen separation membrane system is essential to the coming hydrogen economy. The project of hydrogen separation membrane based on Mixed ionic and electronic conductor (MIEC) composite was initiated by DoE years ago, and the MIEC membrane has been developed in Argonne National Laboratory (ANL) for several years. The goal at ANL is to develop a dense, ceramic-based MIEC membrane that is highly selective, chemical stable in practical environments at operative temperatures up to ≈900°C, and can separate hydrogen from mixed gases at commercially significant fluxes under industrially relevant operating conditions, without the need for electrodes or electrical circuitry. The effort at ANL initially focused on BCY20 (BaCe0.8Y 0.2O3). BCY20 forms the matrix of ANL-1a and -2a ceramic-metal composite membranes (40-50 vol.% of a metal is dispersed in a ceramic matrix) and its bulk transport properties, including ionic transfer number, ionic and electronic conductivity, and chemical and mechanical stability have been systematically studied. However, exposure to CO2 and H2O-containing atmospheres, as would be present in a practical environment, will degrade the material as it reacts to form insulating barium carbonate (BaCO3 ) and cerium oxide (CeO2). This decomposition greatly limits its applicability in hydrogen separation, despite the promising

  8. Ceramic fragments and metal-free full crowns: a conservative esthetic option for closing diastemas and rehabilitating smiles.

    Science.gov (United States)

    Miranda, M E; Olivieri, K A; Rigolin, F J; Basting, R T

    2013-01-01

    Dental ceramics make it possible to restore anterior teeth that have been esthetically compromised, presenting a high resistance to wear, biocompatibility, color stability, and low thermal conductivity. The development of different types of ceramic and techniques for adhesive cementation have made it possible to produce more conservative restorations without involving the healthy dental structure and with minimally invasive preparation, such as the bonding of ceramic fragments. The purpose of this article is to describe a clinical case in which diastemas were closed by using nanofluorapatite ceramic (e.max Ceram, Ivoclar-Vivadent) fragments on teeth 7 and 10 with minimal tooth preparation and metal-free ceramic crowns (e-max Ceram) reinforced with zirconia copings through a computer-aided design/computer-aided manufacturing system (Lava, 3M-ESPE) on teeth 8 and 9.

  9. FY 1998 annual report on the study on development of corrosion-resistant ceramic materials for garbage incinerators; 1998 nendo gomi shori shisetsuyo taishoku ceramics zairyo no kaihatsu ni kansuru kenkyu chosa hokokusho

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1999-03-01

    Described herein are the FY 1988 results of development of corrosion-resistant ceramic materials for garbage incinerators. Residue released when porcelain stocks are collected is selected as the inexpensive stock for SiO{sub 2}-Al{sub 2}O{sub 3}-based refractory materials. It is incorporated with carbon black and reduced at 1,200 to 1,500 degrees C in a nitrogen atmosphere. Synthesis of the target Si-Al-C-N-O-based compound succeeds in the presence of a solid catalyst, but it is a fine powder, and hence that of the massive compound fails. The commercial ceramic materials and new refractory materials, made on a trial basis, are evaluated for their resistance to corrosion using fry ashes collected from a commercial incinerator. These ashes are higher in melting point, more viscous, holding a larger quantity of attached slag and more corrosive than synthetic ashes. These materials are corroded acceleratedly as temperature increases to 1,200 degrees C or higher, more noted with the ceramic materials than with the refractory materials. Oxidation and melting characteristics of the molten slag affect corrosion of some materials. Use of the graphite-based material shall be limited to a section below the slag surface, where graphite is oxidized to a smaller extent. The MgO-based material is promising. The Al{sub 2}O{sub 3}-Cr{sub 2}O{sub 3}-based material is more promising than any other material developed in this study. Their bending strength before and after the corrosion test is measured at normal temperature to 1,700 degrees C, to investigate their deterioration by high temperature and corrosion. (NEDO)

  10. Multilayered ceramic/metal composites by extrusion freeform fabrication

    Science.gov (United States)

    Kasichainula, Sridhar

    Metal layers within a laminar ceramic can improve damage tolerance of ceramics by arresting large cracks either by ductile bridging or by crack deflection at the ceramic/metal interface, which will allow engineers to design reliable ceramics for structural applications. At low volume fractions of the metal ductile bridging is not very effective, mainly owing to decreased distance between the crack tip and next ceramic layer. Significant increase in the energy absorption during fracture can come from delamination, but depends on the interfacial fracture resistance. A two-fold increase in energy absorption is realized in the case of glass-ceramic/silver laminates prepared by extrusion freeform fabrication. Interfacial fracture energy for glass-ceramic/silver is found to be 100 J/m2 in comparison to 15 J/m2 for glass-ceramic/SiC, which should explain the sporadic crack deflection in notched four-point bend. For a short beam flexural test shear failure is more favorable in four-point than in three-point bending. In four-point tests, the shear stresses between the outer and inner loading pins can precipitate shear delamination prior to tensile cracking of the layers. Damage modes under low velocity impact tests are similar to four-point bend showing delamination as primary energy dissipation mechanism.

  11. Core-shell structured ceramic nonwoven separators by atomic layer deposition for safe lithium-ion batteries

    Science.gov (United States)

    Shen, Xiu; Li, Chao; Shi, Chuan; Yang, Chaochao; Deng, Lei; Zhang, Wei; Peng, Longqing; Dai, Jianhui; Wu, Dezhi; Zhang, Peng; Zhao, Jinbao

    2018-05-01

    Safety is one of the most factors for lithium-ion batteries (LIBs). In this work, a novel kind of ceramic separator with high safety insurance is proposed. We fabricated the core-shell nanofiber separators for LIBs by atomic layer deposition (ALD) of 30 nm Al2O3 on the electrospinning nonwoven fiber of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP). The separators show a pretty high heat resistance up to 200 °C without any shrinkage, an excellent fire-resistant property and a wide electrochemical window. Besides, with higher uptake and ionic conductivity, cells assembled with the novel separator shows better electrochemical performance. The ALD produced separators exhibit great potential in elaborate products like 3C communications and in energy field with harsh requirements for safety such as electric vehicles. The application of ALD on polymer fiber membranes brings a new strategy and opportunity for improving the safety of the advanced LIBs.

  12. Synthesis and electrical properties of BaBiO3 and high resistivity BaTiO3–BaBiO3 ceramics

    Directory of Open Access Journals (Sweden)

    Nitish Kumar

    2016-12-01

    Full Text Available Ceramics of the composition BaBiO3 (BB were sintered in oxygen to obtain a single phase with monoclinic I2/m symmetry as suggested by high-resolution X-ray diffraction. X-ray photoelectron spectroscopy confirmed the presence of bismuth in two valence states — 3+ and 5+. Optical spectroscopy showed presence of a direct bandgap at ∼ 2.2eV and a possible indirect bandgap at ∼ 0.9eV. This combined with determination of the activation energy for conduction of 0.25eV, as obtained from ac impedance spectroscopy, suggested that a polaron-mediated conduction mechanism was prevalent in BB. The BB ceramics were crushed, mixed with BaTiO3 (BT, and sintered to obtain BT–BB solid solutions. All the ceramics had tetragonal symmetry and exhibited a normal ferroelectric-like dielectric response. Using ac impedance and optical spectroscopy, it was shown that resistivity values of BT–BB were orders of magnitude higher than BT or BB alone, indicating a change in the fundamental defect equilibrium conditions. A shift in the site occupancy of Bi to the A-site is proposed to be the mechanism for the increased electrical resistivity.

  13. Structural, dielectric and ferroelectric study of (1-ϕ)(NBT-KNN)-ϕSBexT ceramics

    Science.gov (United States)

    Swain, Sridevi; Kumar, Pawan

    2016-11-01

    (1-ϕ)(0.93 Na0.5Bi0.5TiO3-0.07K0.5Na0.5NbO3)-ϕSr0.8Bi2.15Ta2O9/(1-ϕ)(NBT-KNN)-ϕSBexT (ϕ=0, 2, 4, 8, 12, 16 wt%) ceramic samples were synthesized by conventional solid state reaction route. Secondary phases started developing for higher SBexT content in the (1-ϕ)(NBT-KNN)-ϕSBexT ceramic samples. Decrease of transition temperature (Tm) with the increase of SBexT content in (1-ϕ)(NBT-KNN)-ϕSBexT ceramics was attributed to the increase of internal stress. Remnant polarization (Pr), leakage current density and polarization degradation values reduced with the increase of SBexT content in (1-ϕ)(NBT-KNN)-ϕSBexT ceramic samples. Retention of good ferroelectric properties and enhancement of fatigue-free behavior with the incorporation of SBexT phase in (1-ϕ)(NBT-KNN)-ϕSBexT ceramic samples suggested their usefulness for ferroelectric memory applications.

  14. Development of wear resistant ceramic coatings for diesel engine components. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Haselkorn, M.H. [Caterpillar, Inc., Peoria, IL (United States)

    1992-04-01

    Improved fuel economy and a reduction of emissions can be achieved by insulation of the combustion chamber components to reduce heat rejection. However, insulating the combustion chamber components will also increase the operating temperature of the piston ring/cylinder liner interface from approximately 150{degree}C to over 300{degree}C. Existing ring/liner materials can not withstand these higher operating temperatures and for this reason, new materials need to be developed for this critical tribological interface. The overall goal of this program is the development of piston ring/cylinder liner material pairs which would be able to provide the required friction and wear properties at these more severe operating conditions. More specifically, this program first selected, and then evaluated, potential d/wear resistant coatings which could be applied to either piston rings an or cylinder liners and provide, at 350{degree}C under lubricated conditions, coefficients of friction below 0.1 and wear rates of less than 25 {times} lO{sup {minus}6} mm/hour. The processes selected for applying the candidate wear resistant coatings to piston rings and/or cylinder liners were plasma spraying, chemical vapor, physical vapor and low temperature arc vapor deposition techniques as well as enameling techniques.

  15. The features of ceramic materials structure formation when using hard-melting wastes of thermal power stations in charge stock

    Science.gov (United States)

    Skripnikova, Nelli; Yuriev, Ivan; Lutsenko, Alexander; Litvinova, Viktoriya

    2016-01-01

    The paper presents the analysis of aluminum silicate waste generated by thermal power station of the city of Seversk, Tomsk region, Russia. The chemical compositions of aluminum silicate waste are detected and the efficient mixture compositions with the addition of aluminum silicate waste are suggested herein. Ceramic brick structure formation is studied in this paper using X-ray phase and SEM analyses. It is identified that the formed vitreous phase facilitates such strengthening structural modifications as sintering out of pores and shrinkage of unmelted aluminum silicate particles with the following formation of a monolithic product.

  16. Intercalated Nanocomposites Based on High-Temperature Superconducting Ceramics and Their Properties

    Directory of Open Access Journals (Sweden)

    Sevan Davtyan

    2009-12-01

    Full Text Available High temperature superconducting (SC nanocomposites based on SC ceramics and various polymeric binders were prepared. Regardless of the size of the ceramics’ grains, the increase of their amount leads to an increase of resistance to rupture and modulus and a decrease in limiting deformation, whereas an increase in the average ceramic grain size worsens resistance properties. The SC, thermo-chemical, mechanical and dynamic-mechanical properties of the samples were investigated. Superconducting properties of the polymer ceramic nanocomposites are explained by intercalation of macromolecule fragments into the interstitial layer of the ceramics’ grains. This phenomenon leads to a change in the morphological structure of the superconducting nanocomposites.

  17. Heat resistant/radiation resistant cable and incore structure test device for FBR type reactor

    International Nuclear Information System (INIS)

    Tanimoto, Hajime; Shiono, Takeo; Sato, Yoshimi; Ito, Kazumi; Sudo, Shigeaki; Saito, Shin-ichi; Mitsui, Hisayasu.

    1995-01-01

    A heat resistant/radiation resistant coaxial cable of the present invention comprises an insulation layer, an outer conductor and a protection cover in this order on an inner conductor, in which the insulation layer comprises thermoplastic polyimide. In the same manner, a heat resistant/radiation resistant power cable has an insulation layer comprising thermoplastic polyimide on a conductor, and is provided with a protection cover comprising braid of alamide fibers at the outer circumference of the insulation layer. An incore structure test device for an FBR type reactor comprises the heat resistant/radiation resistant coaxial cable and/or the power cable. The thermoplastic polyimide can be extrusion molded, and has excellent radiation resistant by the extrusion, as well as has high dielectric withstand voltage, good flexibility and electric characteristics at high temperature. The incore structure test device for the FBR type reactor of the present invention comprising such a cable has excellent reliability and durability. (T.M.)

  18. Design, Synthesis, and Chemical Processing of Hierarchical Ceramic Structures for Aerospace Applications

    Science.gov (United States)

    1993-03-30

    mixing of reagents : In "si- nitride, for example, has been prepared from a pseuda- multaneous precipitation," all substances whose solu- boehmite sol that...Evaporative Decomposition of 32. F. Tebbe , P.A. Morris, R.H. French, U. Chowdhry, Solutions," I. Am. Ceram. Soc., 72 1811 (1989). and R.L. Coble, "Purity of...F.N. Tebbe , and AJ. Vega, "Studies on Silicon Nitride Powder from Silica Reduction," J. Organoaluminum Precursors of Aluminum Nitride Am. Ceram. Soc

  19. Synthesis, structural characterization of nano ZnTiO3 ceramic: An effective azo dye adsorbent and antibacterial agent

    Directory of Open Access Journals (Sweden)

    R.S. Raveendra

    2014-12-01

    Full Text Available Nanocrystalline meta-zinc titanate (ZnTiO3 ceramic was prepared using a self-propagating solution combustion synthesis (SCS for the first time using urea as fuel. The product was calcined at 800 °C for 2 h to improve the crystallinity. Powder X-ray diffraction (PXRD, Fourier transform infrared spectroscopy (FTIR, scanning electron microscopy (SEM, energy-dispersive X-ray spectroscopy (EDAX, high resolution transmission electron microscopy (HR-TEM and UV–vis absorption spectroscopy were used to characterize the final product. PXRD results show that the ilmenite type rhombohedral structure was formed when the sample was calcined at 800 °C for 2 h. Adsorption experiments were performed with cationic malachite green (MG dye. ∼96% dye was adsorbed onto nanocrystalline ZnTiO3 ceramic at pH 9 for 30 min of the contact time. The optimum adsorbent dose was found to be 0.45 g/L of dye. Langmuir–Hinshelwood model was used to study adsorption kinetics and first order kinetic model best describes the MG adsorption on ZnTiO3. Antibacterial activity was investigated against gram negative Klebsiella aerogenes, Pseudomonas desmolyticum, Escherichia coli, and gram positive Staphylococcus aureus bacteria by agar well diffusion method. Nanocrystalline ZnTiO3 ceramic showed significant effect on all the four bacterial strains at the concentration of 1000 and 1500 μg per well.

  20. Studies and mechanical properties of a new type of 'hybrid' ceramic block for buildings in structural masonry

    International Nuclear Information System (INIS)

    Camara, Cassio Freire; Gomes, Uilame Umbelino

    2012-01-01

    This paper presents the development of a hybrid ceramic block to the use of resides in the buildings executed with structural masonry. This work seeking new materials and / or products with the purpose of increasing the compressive strength of the ceramic blocks, without neglecting other properties (water absorption and linear shrinkage). After the obtained material (clay powder and crushed), the packaging (in percentages ranging from 0%, 5%, 10% and 15% substitution of crushed clay powder), the identification and measuring (weights and lengths) of the bodies of the test piece, was performed on the approach characterized by fluorescence, mineralogy and SEM of these materials as well as the characterization (SEM) of ceramic blocks after the sintering (temperature of the 900 deg C, 1000 deg C, and 1100 deg C rate with heating tax of 5 o C/minute and soak for 1 hour). Then the samples were subjected to the tests (compressive strength and water absorption) and the respective calculated linear shrinkage. After conducting the analysis of the results of these tests (according to the criteria and parameters required by the ABNT NBR 15270) was found that the 'hybrid' block with the addition of 10% crushed powder obtained the best results, increasing the compressive strength at 16 % without compromising the other parameters required by the Standard. (author)

  1. Effect of Gd substitution on structure and spectroscopic properties of (Lu,Gd)2O3:Eu ceramic scintillator

    Science.gov (United States)

    Cao, Maoqing; Hu, Zewang; Ivanov, Maxim; Dai, Jiawei; Li, Chaoyu; Kou, Huamin; Shi, Yun; Chen, Haohong; Xu, Jiayue; Pan, Yubai; Li, Jiang

    2018-02-01

    In this paper, (Lu1-xGdx)2O3:Eu (x = 0, 0.1, 0.3, 0.5, 0.7, 0.9) ceramics were consolidated by the solid-state reaction method combined with vacuum sintering without sintering aids. We investigated the effect of the varying contents of Gd2O3 on the structure and spectroscopic properties of (Lu1-xGdx)2O3:Eu ceramics. X-ray diffraction (XRD) patterns indicate that proper amount of Gd2O3 can incorporate well with Lu2O3 and form Lu2O3-Gd2O3 solid solution. However, excessive Gd3+-doping in Lu2O3 will lead to the cubic phase transforming into monoclinic even hexagonal phase. The Gd3+ substitution no more than 50% of Lu2O3 enhances the radioluminescence, and reduces the fluorescence lifetime. Transmittance, photoluminescence, and radiation damage of the (Lu1-xGdx)2O3:Eu scintillation ceramics were also studied.

  2. Electrical resistivity of ceramic-metal composite materials in the percolation region: application in crucibles for induction furnaces

    International Nuclear Information System (INIS)

    Sene, Frank Ferrer

    1997-01-01

    Ceramic composite materials were produced by mixing powders of Partially Stabilized (PSZ) with titanium, niobium or nickel, and cristobalite with titanium. Pellets were produced by uniaxially pressing the material followed by cold isostatic pressing and finally sintering at 1600 deg C for 1,5 hours in argon. The metal content was varied in the range of 0-40 volume percent (v/o). Electrical resistivity measurements were performed in the temperature range of 25 - 700 deg C. Samples containing metallic inclusions above 25 v/o show the predominance of electronic type conducting. For samples with metallic inclusion below 25 v/o, a typically ionic conduction behavior has been observed. PSZ-Ti and PSZ-Ni samples containing 25 v/o of metallic inclusions show an insulator - conductor transition in a given temperature range. Cristobalite samples containing 30 v/o of titanium show a conductor - insulator transition also in a specific temperature range. Tests performed in an induction furnace showed that samples containing metallic inclusions above 25 v/o had self-heated when exposed to electro magnetic fields in the range of radio frequency (r.f.) Crucibles of PSZ-Ti were made by slip casting followed by sintering at 1600 deg C for 1.5 hours in argon. These crucibles were exposed to electromagnetic fields in the r.f. range and the maximum temperature reached was 1350 deg C. Microstructure characterization was performed on those materials by X-ray diffraction, EDS, optical and scanning electron microscopy. (author)

  3. Use of residues proceeding from marbles and granites finishing and manufacturing processes as raw material for structural ceramic; Utilizacao do residuo proveniente do acabamento e manufatura de marmores e granitos como materia-prima em ceramica vermelha

    Energy Technology Data Exchange (ETDEWEB)

    Mello, Roberta Monteiro de

    2006-07-01

    In order to decrease environmental impact, caused by mud discarding and clay extraction in the ceramic industry, it was used residual mud from marble and granite companies for structural ceramic. Samples were collected in twelve different marble companies located at the metropolitan region of Sao Paulo. However, only four samples were selected, based on its different characteristics. Clay stone was the raw material chosen to prepare the structural ceramic, considering its high use in this segment. Samples and clay stone were both analysed by the following procedures: granulometric analysis, x-rays fluorescent chemical analysis and x-rays diffraction mineralogical analysis, besides, tests in the samples were conducted following NBR 10004 standards. Once raw materials were characterized, the plasticity test was conducted. Test specimen were molded with different levels of mud, then burned and submitted to technological tests, such as: mechanical resistance, water absorption, porosity, specific gravity and retraction, material dilation before burning process and scanning electron microscopy. The final results have shown the viability of using this kind of mud, and pointed some advantages on its usage, but taking in consideration some previous conditions to be adopted. (author)

  4. Ceramic piezoelectric materials

    International Nuclear Information System (INIS)

    Kaszuwara, W.

    2004-01-01

    Ceramic piezoelectric materials conert reversibility electric energy into mechanical energy. In the presence of electric field piezoelectric materials exhibit deformations up to 0.15% (for single crystals up to 1.7%). The deformation energy is in the range of 10 2 - 10 3 J/m 3 and working frequency can reach 10 5 Hz. Ceramic piezoelectric materials find applications in many modern disciplines such as: automatics, micromanipulation, measuring techniques, medical diagnostics and many others. Among the variety of ceramic piezoelectric materials the most important appear to be ferroelectric materials such as lead zirconate titanate so called PZT ceramics. Ceramic piezoelectric materials can be processed by methods widely applied for standard ceramics, i.e. starting from simple precursors e.g. oxides. Application of sol-gel method has also been reported. Substantial drawback for many applications of piezoelectric ceramics is their brittleness, thus much effort is currently being put in the development of piezoelectric composite materials. Other important research directions in the field of ceramic piezoelectric materials composite development of lead free materials, which can exhibit properties similar to the PZT ceramics. Among other directions one has to state processing of single crystals and materials having texture or gradient structure. (author)

  5. Frost resistance of fibre reinforced concrete structures

    DEFF Research Database (Denmark)

    Hansen, Ernst Jan De Place

    1999-01-01

    Frost resistance of fibre reinforced concrete with 2.5-4.2% air and 6-9% air (% by volume in fresh concrete) casted in the laboratory and in-situ is compared. Steel fibres with hooked ends (ZP, length 30 mm) and polypropylene fibres (PP, CS, length 12 mm) are applied. It is shown that· addition...... of 0.4-1% by volume of fibres cannot replace air entrainment in order to secure a frost resistant concrete; the minimum amount of air needed to make the concrete frost resistant is not changed when adding fibres· the amount of air entrainment must be increased when fibres are added to establish...

  6. Frost resistance of fibre reinforced concrete structures

    DEFF Research Database (Denmark)

    Hansen, Ernst Jan De Place

    1999-01-01

    of 0.4-1% by volume of fibres cannot replace air entrainment in order to secure a frost resistant concrete; the minimum amount of air needed to make the concrete frost resistant is not changed when adding fibres· the amount of air entrainment must be increased when fibres are added to establish......Frost resistance of fibre reinforced concrete with 2.5-4.2% air and 6-9% air (% by volume in fresh concrete) casted in the laboratory and in-situ is compared. Steel fibres with hooked ends (ZP, length 30 mm) and polypropylene fibres (PP, CS, length 12 mm) are applied. It is shown that· addition...

  7. Structure and properties of porous ceramic preforms made of α-alumina particles

    Directory of Open Access Journals (Sweden)

    J. W. Kaczmar

    2010-01-01

    Full Text Available Properties of ceramic preforms made of α-alumina particles for strengthening of metal based composite materials manufactured by squeeze casting are discussed in the paper. Composite materials strengthened with ceramic particles can be then plastically worked in order to remove the residual porosity and give the final net shape. There was investigated the permeability of porous preforms as the measure of the open porosity making possible the infiltration process with the molten metal, compression strength, bending strength and shear strength determining the stability of porous ceramic preforms during infiltration. Performed investigations allow to ascertain the occurrence of the open porosity in the porous preforms and strong effect of porosity on permeability. The largest permeability of 19 m2/Pa·s showed porous preforms characterized by porosity the of 90%. The strength properties increased with the decrease of preforms porosity and the prerforms characterized by 60% of porosity were characterized by the largest strength properties (bending strength Rg =7 MPa, compression strength Rc = 11.5 MPa, shear strength Rt = 4.0 MPa. The microscopic observations of fractures surfaces allow to evaluate quality and forming phenomena of the binder bridges connecting the ceramic particles.

  8. Copper-silver-titanium-tin filler metal for direct brazing of structural ceramics

    Science.gov (United States)

    Moorhead, Arthur J.

    1988-04-05

    A method of joining ceramics and metals to themselves and to one another at about 800.degree. C. is described using a brazing filler metal consisting essentially of 35 to 50 at. % copper, 40 to 50 at. % silver, 1 to 15 at. % titanium, and 2 to 8 at. % tin. This method produces strong joints that can withstand high service temperatures and oxidizing environments.

  9. Copper-silver-titanium filler metal for direct brazing of structural ceramics

    Science.gov (United States)

    Moorhead, Arthur J.

    1987-01-01

    A method of joining ceramics and metals to themselves and to one another is described using a brazing filler metal consisting essentially of 35 to 50 atomic percent copper, 15 to 50 atomic percent silver and 10 to 45 atomic percent titanium. This method produces strong joints that can withstand high service temperatures and oxidizing environments.

  10. Structure-property relationship of ceramic coatings on metals produced by laser processing

    NARCIS (Netherlands)

    de Hosson, J.T.M.; van den Burg, M.; Mazumder, J; Conde, O; Villar, R; Steen, W

    1996-01-01

    This paper concentrates on the mechanical performance of various ceramic coatings of Cr2O3 on steel (SAF2205), as produced by CO2 laser processing. The thickness of the coating that can be applied by laser coating is limited to about 200 mu m setting a limit to the maximum strain energy release rate

  11. Structural, dielectric and magnetic properties of cobalt ferrite prepared using auto combustion and ceramic route

    International Nuclear Information System (INIS)

    Murugesan, C.; Perumal, M.; Chandrasekaran, G.

    2014-01-01

    Cobalt ferrite is synthesized by using low temperature auto combustion and high temperature ceramic methods. The prepared samples have values of lattice constant equal to 8.40 Å and 8.38 Å for auto combustion and ceramic methods respectively. The FTIR spectrum of samples of the auto combustion method shows a high frequency vibrational band at 580 cm −1 assigned to tetrahedral site and a low frequency vibrational band at 409 cm −1 assigned to octahedral site which are shifted to 590 cm −1 and 412 cm −1 for the ceramic method sample. SEM micrographs of samples show a substantial difference in surface morphology and size of the grains between the two methods. The frequency dependent dielectric constant and ac conductivity of the samples measured from 1 Hz to 2 MHz at room temperature are reported. The room temperature magnetic hysteresis parameters of the samples are measured using VSM. The measured values of saturation magnetization, coercivity and remanent magnetization are 42 emu/g, 1553 Oe, 18.5 emu/g for the auto combustion method, 66.7 emu/g, 379.6 Oe, and 17.3 emu/g for the ceramic method, respectively. The difference in preparation methods and size of the grains causes interesting changes in electrical and magnetic properties

  12. Probability based high temperature engineering creep and structural fire resistance

    CERN Document Server

    Razdolsky, Leo

    2017-01-01

    This volume on structural fire resistance is for aerospace, structural, and fire prevention engineers; architects, and educators. It bridges the gap between prescriptive- and performance-based methods and simplifies very complex and comprehensive computer analyses to the point that the structural fire resistance and high temperature creep deformations will have a simple, approximate analytical expression that can be used in structural analysis and design. The book emphasizes methods of the theory of engineering creep (stress-strain diagrams) and mathematical operations quite distinct from those of solid mechanics absent high-temperature creep deformations, in particular the classical theory of elasticity and structural engineering. Dr. Razdolsky’s previous books focused on methods of computing the ultimate structural design load to the different fire scenarios. The current work is devoted to the computing of the estimated ultimate resistance of the structure taking into account the effect of high temperatur...

  13. 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.

  14. Structural resistance of cashew ( Anacardium occidentale ) against ...

    African Journals Online (AJOL)

    Using artificial inoculation, mildew infection was possible on young leaves, but infection did not occur on older leaves. Epicuticular wax layer observed on cashew leaf surface, as a pre-infection resistance factor, appeared to be responsible for inhibition of germination and development of O. anacardii on older leaves.

  15. Effect of temperature on structure and corrosion resistance for ...

    Indian Academy of Sciences (India)

    Abstract. The effect of plating temperatures between 60 and 90◦C on structure and corrosion resistance for elec- troless NiWP coatings on AZ91D magnesium alloy substrate was investigated. Results show that temperature has a significant influence on the surface morphology and corrosion resistance of the NiWP alloy ...

  16. Effect of temperature on structure and corrosion resistance for ...

    Indian Academy of Sciences (India)

    The effect of plating temperatures between 60 and 90 ∘ C on structure and corrosion resistance for electroless NiWP coatings on AZ91D magnesium alloy substrate was investigated. Results show that temperature has a significant influence on the surface morphology and corrosion resistance of the NiWP alloy coating.

  17. Preparation, Structure, and Dielectric and Magnetic Properties of SrFe2/3W1/3O3 Ceramics

    Science.gov (United States)

    Pavlenko, A. V.; Turik, A. V.; Shilkina, L. A.; Kubrin, S. P.; Rusalev, Yu. V.; Reznichenko, L. A.; Andryushina, I. N.

    2018-03-01

    Polycrystalline samples of SrFe2/3W1/3O3 (SFWO) ceramic were obtained by solid-phase reactions with subsequent sintering using conventional ceramic technology. X-ray diffraction analysis showed that at room temperature, the SFWO ceramic is single-phase and has a perovskite-type structure with tetragonal symmetry and parameters a = 3.941(9) Å, c = 3.955(6) Å, and c/a = 1.0035. In studying the magnetic properties and the Mössbauer effect in SFWO ceramics, it is found that the material is a ferrimagnet, and the iron ions are only in the valence state of Fe3+. It is suggested that in the temperature range of T = 150-210°C, a smeared phase transition from a cubic (paraelectric) phase to a tetragonal (ferroelectric) phase takes place in SFWO with decreasing temperature.

  18. Structural and electromechanical properties of Na0.5Bi0.5TiO3 ceramics produced by different synthesis routes

    Science.gov (United States)

    Hussain, A.; Maqbool, A.; Malik, R. A.; Kim, M. H.; Song, T. K.; Kim, W. J.

    2016-08-01

    Sodium bismuth titanate, Na0.5Bi0.5TiO3 (NBT) ceramics were produced by three different methods; conventional mixed-oxide (CMO) route, molten salt synthesis (MSS) and topochemical microcrystal conversion (TMC) and then sintered at 1150 oC for 2 h in air atmosphere. The crystal structure, dielectric, ferroelectric and field-induced strain properties were investigated for all samples. All samples showed a single phase perovskite structure without any evidences of unwanted secondary phases. The NBT ceramics synthesized by the TMC method show slightly better dielectric, ferroelectric and field induced strain response as compared with CMO and MSS synthesized ceramics. The room temperature dielectric constant measured at 1 kHz increased from 218 for NBT ceramics synthesized by MSS method to 271 and 330 for CMO and TMC synthesized ceramics, respectively. Similarly, the dynamic piezoelectric coefficient (d 33*) enhanced from 91 pm/V for CMO synthesized to 97 pm/V and 107 pm/V for MSS and TMC synthesized ceramics, respectively.

  19. Investigation on Structural and Optical Properties of Willemite Doped Mn2+ Based Glass-Ceramics Prepared by Conventional Solid-State Method

    Directory of Open Access Journals (Sweden)

    Nur Farhana Samsudin

    2015-01-01

    Full Text Available Mn-doped willemite (Zn2SiO4:Mn2+ glass-ceramics derived from ZnO-SLS glass system were prepared by a conventional melt-quenching technique followed by a controlled crystallization step employing the heat treatment process. Soda lime silica (SLS glass waste, ZnO, and MnO were used as sources of silicon, zinc, and manganese, respectively. The obtained glass-ceramic samples were characterized using the X-ray diffraction (XRD, Field Emission Scanning Electron Microscopy (FESEM, Fourier Transform Infrared (FTIR, UV-Visible (UV-Vis, and photoluminescence (PL spectroscopy. The results of XRD revealed that ZnO crystal and willemite (β-Zn2SiO4 were presented as major embedded crystalline phases. This observation was consistent with the result of FESEM which showed the presence of irregularity in shape and size of willemite crystallites. FTIR spectroscopy exhibits the structural evolution of willemite based glass-ceramics. The optical band gap shows a decreasing trend as the Mn-doping content increased. Photoluminescent technique was applied to characterize the role of Mn2+ ions when entering the willemite glass-ceramic structure. By measuring the excitation and emission spectra, the main emission peak of the glass-ceramic samples located at a wavelength of 585 nm after subjecting to 260 nm excitations. The following results indicate that the obtained glass-ceramics can be applied as phosphor materials.

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

    Directory of Open Access Journals (Sweden)

    Mendes A.M.

    2017-02-01

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

  1. Large Piezoelectric Strain with Superior Thermal Stability and Excellent Fatigue Resistance of Lead-Free Potassium Sodium Niobate-Based Grain Orientation-Controlled Ceramics.

    Science.gov (United States)

    Quan, Yi; Ren, Wei; Niu, Gang; Wang, Lingyan; Zhao, Jinyan; Zhang, Nan; Liu, Ming; Ye, Zuo-Guang; Liu, Liqiang; Karaki, Tomoaki

    2018-03-19

    Environment-friendly lead-free piezoelectric materials with high piezoelectric response and high stability in a wide temperature range are urgently needed for various applications. In this work, grain orientation-controlled (with a 90% ⟨001⟩ c -oriented texture) (K,Na)NbO 3 -based ceramics with a large piezoelectric response ( d 33 *) = 505 pm V -1 and a high Curie temperature ( T C ) of 247 °C have been developed. Such a high d 33 * value varies by less than 5% from 30 to 180 °C, showing a superior thermal stability. Furthermore, the high piezoelectricity exhibits an excellent fatigue resistance with the d 33 * value decreasing within only by 6% at a field of 20 kV cm -1 up to 10 7 cycles. These exceptional properties can be attributed to the vertical morphotropic phase boundary and the highly ⟨001⟩ c -oriented textured ceramic microstructure. These results open a pathway to promote lead-free piezoelectric ceramics as a viable alternative to lead-based piezoceramics for various practical applications, such as actuators, transducers, sensors, and acoustic devices, in a wide temperature range.

  2. Structural Basis of Protein Oxidation Resistance: A Lysozyme Study

    OpenAIRE

    Girod, Marion; Enjalbert, Quentin; Brunet, Claire; Antoine, Rodolphe; Lemoine, Jérôme; Lukac, Iva; Radman, Miroslav; Krisko, Anita; Dugourd, Philippe

    2014-01-01

    Accumulation of oxidative damage in proteins correlates with aging since it can cause irreversible and progressive degeneration of almost all cellular functions. Apparently, native protein structures have evolved intrinsic resistance to oxidation since perfectly folded proteins are, by large most robust. Here we explore the structural basis of protein resistance to radiation-induced oxidation using chicken egg white lysozyme in the native and misfolded form. We study the differential resistan...

  3. The DC Electrical Resistivity Curves of Bismuth-2212 Ceramic Superconductors: Evaluation of the Hole-Carrier Concentrations per-Cu Ion

    Directory of Open Access Journals (Sweden)

    nurmalita .

    2016-04-01

    Full Text Available In this study the samples of Bismuth ceramic superconductors were synthesized by the melt textured growth methods from a 2212 stoichiometric composition in order to obtain a large amount of pure Bi-2212. The effects of Pb substitution on the properties of Bi-based Bi2−xPbxSr2CaCu2Oy superconductor with x = 0, 0.2, and 0.4 were investigated by means of DC electrical resistivity measurements. It has been found that the hole-carrier concentrations per-Cu ion of the samples change independently of Pb content.

  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. Ion conductivity of nasicon ceramics

    International Nuclear Information System (INIS)

    Hoj, J.W.; Engell, J.

    1989-01-01

    The Nasicon ss ,Na 1 + X Zr 2 Si X P 3 - X O 12 o , X , 3, includes some of the best solid state sodium conductors known today. Compositions in the interval 1.6 , X , 2.6 show conductivities comparable to the best β double-prime-alumina ceramics. It is well known that the ion conductivity of β-alumina is strongly dependent on the texture of the ceramic. Here a similar behavior is reported for Nasicon ceramics. Ceramics of the bulk composition Na 2.94 Zr 1.49 Si 2.20 P 0.80 O 10.85 were prepared by a gel method. The final ceramics consist of Nasicon crystals with x = 2.14 and a glass phase. The grain size and texture of the ceramics were controlled by varying the thermal history of the gel based raw materials and the sintering conditions. The room temperature resistivity of the resulting ceramics varies from 3.65*10 3 ohm cm to 1.23*10 3 ohm cm. Using the temperature comparison method and estimates of the area of grain boundaries in the ceramics, the resistivity of the Nasicon phase is estimated to be 225 ohm cm at 25 degrees C. B 2 O 3 - or Al 2 O 3 -doping of the glass bearing Nasicon ceramic lower the room temperature resistivity by a factor 2 to 5. The dopants do not substitute into the Nasicon phase in substantial amounts

  6. Sustainable And Earthquake Resistant Structural Systems

    OpenAIRE

    Coşkun, Erdal; Kıymaz, Güven; Seçkin, Edip

    2010-01-01

    Sustainable design, which is one of the most important considerations in any structural design project nowadays, implies many factors such as environmental friendliness, energy competence, functionality, adaptability and efficient use of world's resources. Sustainable design is not only the realization of an architect's vision, but also the notion of the structural engineering regulation. As a result of close cooperation between architects and structural engineers, many brilliant and ele...

  7. Resistant Starch Regulates Gut Microbiota: Structure, Biochemistry and Cell Signalling.

    Science.gov (United States)

    Yang, Xiaoping; Darko, Kwame Oteng; Huang, Yanjun; He, Caimei; Yang, Huansheng; He, Shanping; Li, Jianzhong; Li, Jian; Hocher, Berthold; Yin, Yulong

    2017-01-01

    Starch is one of the most popular nutritional sources for both human and animals. Due to the variation of its nutritional traits and biochemical specificities, starch has been classified into rapidly digestible, slowly digestible and resistant starch. Resistant starch has its own unique chemical structure, and various forms of resistant starch are commercially available. It has been found being a multiple-functional regulator for treating metabolic dysfunction. Different functions of resistant starch such as modulation of the gut microbiota, gut peptides, circulating growth factors, circulating inflammatory mediators have been characterized by animal studies and clinical trials. In this mini-review, recent remarkable progress in resistant starch on gut microbiota, particularly the effect of structure, biochemistry and cell signaling on nutrition has been summarized, with highlights on its regulatory effect on gut microbiota. © 2017 The Author(s). Published by S. Karger AG, Basel.

  8. Fracture resistance enhancement of layered structures by multiple cracks

    DEFF Research Database (Denmark)

    Goutianos, Stergios; Sørensen, Bent F.

    2016-01-01

    A theoretical model is developed to test if the fracture resistance of a layered structure can be increased by introducing weak layers changing the cracking mechanism. An analytical model, based on the J integral, predicts a linear dependency between the number of cracks and the steady state...... fracture resistance. A finite element cohesive zone model, containing two cracking planes for simplicity, is used to check the theoretical model and its predictions. It is shown that for a wide range of cohesive law parameters, the numerical predictions agree well quantitatively with the theoretical model....... Thus, it is possible to enhance considerably the fracture resistance of a structure by adding weak layers....

  9. Linking microbial community structure and function to characterize antibiotic resistant bacteria and antibiotic resistant genes from cattle feces

    Science.gov (United States)

    There is widespread interest in monitoring the development of antibiotic resistant bacteria and antibiotic resistance genes in agriculturally impacted environments, however little is known about the relationships between bacterial community structure, and antibiotic resistance gene profiles. Cattl...

  10. Highly-translucent, strong and aging-resistant 3Y-TZP ceramics for dental restoration by grain boundary segregation.

    Science.gov (United States)

    Zhang, Fei; Vanmeensel, Kim; Batuk, Maria; Hadermann, Joke; Inokoshi, Masanao; Van Meerbeek, Bart; Naert, Ignace; Vleugels, Jef

    2015-04-01

    Latest trends in dental restorative ceramics involve the development of full-contour 3Y-TZP ceramics which can avoid chipping of veneering porcelains. Among the challenges are the low translucency and the hydrothermal stability of 3Y-TZP ceramics. In this work, different trivalent oxides (Al2O3, Sc2O3, Nd2O3 and La2O3) were selected to dope 3Y-TZP ceramics. Results show that dopant segregation was a key factor to design hydrothermally stable and high-translucent 3Y-TZP ceramics and the cation dopant radius could be used as a controlling parameter. A large trivalent dopant, oversized as compared to Zr(4+), exhibiting strong segregation at the ZrO2 grain boundary was preferred. The introduction of 0.2 mol% La2O3 in conventional 0.1-0.25 wt.% Al2O3-doped 3Y-TZP resulted in an excellent combination of high translucency and superior hydrothermal stability, while retaining excellent mechanical properties. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  11. Alumina-zirconium ceramics synthesis by selective laser sintering/melting

    International Nuclear Information System (INIS)

    Shishkovsky, I.; Yadroitsev, I.; Bertrand, Ph.; Smurov, I.

    2007-01-01

    In the present paper, porous refractory ceramics synthesized by selective laser sintering/melting from a mixture of zirconium dioxide, aluminum and/or alumina powders are subjected to optical metallography and X-ray analysis to study their microstructure and phase composition depending on the laser processing parameters. It is shown that high-speed laser sintering in air yields ceramics with dense structure and a uniform distribution of the stabilizing phases. The obtained ceramic-matrix composites may be used as thermal and electrical insulators and wear resistant coating in solid oxide fuel cells, crucibles, heating elements, medical tools. The possibility to reinforce refractory ceramics by laser synthesis is shown on the example of tetragonal dioxide of zirconium with hardened micro-inclusion of Al 2 O 3 . By applying finely dispersed Y 2 O 3 powder inclusions, the type of the ceramic structure is significantly changed

  12. Piezoelectric Ceramics

    International Nuclear Information System (INIS)

    Park, Chang Yeop

    1987-03-01

    This book tells of piezoelectric ceramics on BaTiO 3 Pb(Zr, Ti)O 3 , properties of piezoelectric ceramics, measurement method of piezoelectric ceramics, manufacturing method of piezoelectric ceramics, property of PbZrO 3 -PbTiO 3 , transparent ceramics like electro-optics effect, electro-optics ceramics, application of a producer of high voltage, application of ultrasonic generator, ZnO piezoelectric film and its application such as property of ZnO, piezoelectric of ZnO film, manufacturing method of ZnO.

  13. 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.

  14. Functional properties of BaTiO3-Ni0.5Zn0.5Fe2O4 magnetoelectric ceramics prepared from powders with core-shell structure

    International Nuclear Information System (INIS)

    Curecheriu, L. P.; Mitoseriu, L.; Postolache, P.; Buscaglia, M. T.; Buscaglia, V.; Ianculescu, A.; Nanni, P.

    2010-01-01

    In the present work, diphasic ceramic composites with core-shell nanostructures formed by Ni 0.50 Zn 0.50 Fe 2 O 4 core and BaTiO 3 shell were investigated. Their properties were compared with those of composites prepared by coprecipitation. The core-shell structure was confirmed by microstructural powder analysis. Homogeneous microstructures with a good phase mixing and percolated dielectric phase by the magnetic one were obtained from coprecipitated powders. Less homogeneous microstructures resulted in ceramics produced from the powder prepared by core-shell method, with isolated small ferrite grains besides large ferrite aggregates embedded into the BaTiO 3 matrix. Both the ferroelectric and magnetic phases preserve their basic properties in bulk composite form. However, important differences in the dielectric relaxation and conduction mechanisms were found as result of the microstructural difference. Extrinsic contributions play important roles in modifying the electric properties in both ceramics, causing space charge effect, Maxwell-Wagner relaxations and hopping conductivity, mainly due to the ferrite low resistivity phase. The conductivity and dielectric modulus spectra analysis allowed to identify different polaron contributions associated with the microstructural differences. It results that by using the core-shell method, improved dielectric properties and limited hopping contributions can be realized.

  15. Lithography-based ceramic manufacture (LCM) of auxetic structures: present capabilities and challenges

    OpenAIRE

    Lantada, Andrés Díaz; de Blas Romero, Adrián; Schwentenwein, Martin; Jellinek, Christopher; Homa, Johannes

    2016-01-01

    Auxetic metamaterials are known for having a negative Poisson's ratio (NPR) and for displaying the unexpected properties of lateral expansion when stretched and densification when compressed. Even though a wide set of micro-manufacturing resources have been used for the development of auxetic metamaterials and related devices, additional precision and an extension to other families of materials is needed for their industrial expansion. In addition, their manufacture using ceramic materials is...

  16. Characterization and evaluation of ceramic properties of clay used in structural ceramics; Caracterizacao e propriedades ceramicas de argilas usadas em ceramica vermelha no estado do Espirito Santo

    Energy Technology Data Exchange (ETDEWEB)

    Savazzini-Reis, A., E-mail: alessandrar@ifes.edu.br [Instituto Federal do Espirito Santo (IFES), Colatina, ES (Brazil); Della-Sagrillo, V.P. [Instituto Federal do Espirito Santo (IFES), Vitoria, ES (Brazil); Valenzuela-Diaz, F.R. [Universidade de Sao Paulo (PMT/EP/USP), SP (Brazil)

    2016-07-01

    The Brazilian red ceramic industry monthly consumes about 10.3 million tons of clay, its main raw material. In most potteries, characterization of the clay is made empirically, which can result in tiles and blocks not according to standards. This sense, this paper aims to characterize clays used in the manufacturing of red ceramic products in factory located in Colatina-ES, which appears as a ceramic pole with about twenty small and midsize industries. The clays were characterized by: Xray fluorescence, X-ray diffraction, thermal analysis (TG/DSC), granulometry and Atterberg limits. Specimens of clay and mixture containing four clays were shaped. Specimens were shaped, dried at 110°C, and burned in a kiln for 24 h. The ceramics and mechanical characteristics were evaluated: flexural strength, water absorption, apparent porosity, apparent specific mass and shrinkage by drying and firing. The characterization showed that kaolinitic clay presents high plasticity, but high porosity. The mixture formed by the four clays does not meet the requirements of the Brazilian standard clays for red ceramic. (author)

  17. Study of the structural and electrical behavior of Bi(Mg,TiO3 modified (Ba,CaTiO3 ceramics

    Directory of Open Access Journals (Sweden)

    Md. Kashif Shamim

    2016-12-01

    Full Text Available The ability of BaTiO3 to form solid solutions with different dopants (both iso- and aliovalent makes it versatile for various applications. In the present study, (Ba,CaTiO3 (BCT is modified with Bi(MgTiO3 (BMT in search for new lead-free ferroelectric material and improve their properties. For this purpose, BCT acts as a main base material and BMT acts as a modifier to fabricate a multifunctional material. In this study, we report the structural and electrical properties of lead free piezo-ceramics (1−x(Ba0.8Ca0.2TiO3–xBi(Mg0.5Ti0.5O3 with x=0.2, 0.4, 0.5 prepared by solid-state sintering technique. Single perovskite phase with tetragonal structure is obtained for all the compositions, which is reconfirmed by the Raman Spectroscopic study. Dielectric study confirm the temperature stable behavior of the dielectric permittivity values above 300∘C. The dielectric constant value decreases with increase in BMT doping content. Impedance Spectroscopic study confirms non-Debye type dielectric relaxation in the specimen. The Nyquist plot and conductivity studies show the negative temperature coefficient of resistance behavior (NTCR of the samples.

  18. Ceramic package fabrication for YMP nuclear waste disposal

    Energy Technology Data Exchange (ETDEWEB)

    Wilfinger, K.

    1994-08-01

    The purpose of this work is to develop alternate materials/design concepts to metal barriers for the Nevada Nuclear Waste Storage Investigations Project. There is some potential that site conditions may prove to be too aggressive for successful employment of the metal alloys under current consideration or that performance assessment models will predict metal container degradation rates that are inconsistent with the goal of substantially complete containment included in the NRC regulations. In the event that the anticipated lifetimes of metal containers are considered inadequate, alternate materials (i.e. ceramics or ceramic/metal composites) will be chosen due to superior corrosion resistance. This document was prepared using information taken from the open literature, conversations and correspondence with vendors, news releases and data presented at conferences to determine what form such a package might take. This discussion presents some ceramic material selection criteria, alternatives for the materials which might be used and alternatives for potential fabrication routes. This includes {open_quotes}stand alone{close_quotes} ceramic components and ceramic coatings/linings for metallic structures. A list of companies providing verbal or written information concerning the production of ceramic or ceramic lined waste containers appears at the end of this discussion.

  19. Processing, Structure and High Temperature Oxidation Properties of Polymer-Derived and Hafnium Oxide Based Ceramic Systems

    Science.gov (United States)

    Terauds, Kalvis

    Demands for hypersonic aircraft are driving the development of ultra-high temperature structural materials. These aircraft, envisioned to sustain Mach 5+, are expected to experience continuous temperatures of 1200--1800°C on the aircraft surface and temperatures as high as 2800°C in combustion zones. Breakthroughs in the development of fiber based ceramic matrix composites (CMCs) are opening the door to a new class of high-tech UHT structures for aerospace applications. One limitation with current carbon fiber or silicon carbide fiber based CMC technology is the inherent problem of material oxidation, requiring new approaches for protective environmental barrier coatings (EBC) in extreme environments. This thesis focuses on the development and characterization of SiCN-HfO2 based ceramic composite EBC systems to be used as a protective layer for silicon carbide fiber based CMCs. The presented work covers three main architectures for protection (i) multilayer films, (ii) polymer-derived HfSiCNO, and (iii) composite SiCN-HfO 2 infiltration. The scope of this thesis covers processing development, material characterization, and high temperature oxidation behavior of these three SiCN-HfO2 based systems. This work shows that the SiCN-HfO 2 composite materials react upon oxidation to form HfSiO4, offering a stable EBC in streaming air and water vapor at 1600°C.

  20. Exoelectron emission from magnesium borate glass ceramics

    International Nuclear Information System (INIS)

    Kawamoto, Takamichi; Yanagisawa, Hideo; Nakamichi, Hiroshi; Kikuchi, Riichi; Kawanishi, Masaharu.

    1986-01-01

    Thermally stimulated exoelectron emission (TSEE) of a magnesium borate glass ceramics was investigated for its application to dosemetric use. It has been found that the TSEE glow patterns of the magnesium borate glass ceramics as well as a Li 2 B 4 O 7 glass ceramics depend on the kind of the radiation used and that the heat resistance of the magnesium borate glass ceramics is higher than that of the Li 2 B 4 O 7 glass ceramics. Therefore, the TSEE glow patterns of the magnesium borate glass ceramics indicate a possibility to be used as the dose measurement for each kind of radiation in the mixed radiation field. (author)

  1. On Ceramics.

    Science.gov (United States)

    School Arts, 1982

    1982-01-01

    Presents four ceramics activities for secondary-level art classes. Included are directions for primitive kiln construction and glaze making. Two ceramics design activities are described in which students make bizarrely-shaped lidded jars, feet, and footwear. (AM)

  2. Piggyback resistive Micromegas

    CERN Document Server

    Attié, D; Durand, D; Desforge, D; Ferrer-Ribas, E; Galán, J; Giomataris, Y; Gongadze, A; Iguaz, F J; Jeanneau, F; de Oliveira, R; Papaevangelou, T; Peyaud, A; Teixeira, A

    2013-01-01

    Piggyback Micromegas consists in a novel readout architecture where the anode element is made of a resistive layer on a ceramic substrate. The resistive layer is deposited on the thin ceramic substrate by an industrial process which provides large dynamic range of resistivity (10$^6$ to 10$^{10}$\\,M$\\Omega$/square). The particularity of this new structure is that the active part is entirely dissociated from the read-out element. This gives a large flexibility on the design of the anode structure and the readout scheme. Without significant loss, signals are transmitted by capacitive coupling to the read-out pads. The detector provides high gas gain, good energy resolution and the resistive layer assures spark protection for the electronics. This assembly could be combined with modern pixel array electronic ASICs. First tests with different Piggyback detectors and configurations will be presented. This structure is adequate for cost effective fabrication and low outgassing detectors. It was designed to perform ...

  3. Study of true-remanent polarization using remanent hysteresis task and resistive leakage analysis in ferroelectric 0.64Pb(Mg1/3Nb2/3)O3-0.36PbTiO3 ceramics

    Science.gov (United States)

    Joseph, Abhilash J.; Kumar, Binay

    2018-03-01

    The conventionally reported value of remanent polarization (Pr) contains contribution from non-remanent components which are not usable for memory device applications. This report presents techniques which extract the true-remanent (intrinsic) component of polarization after eliminating the non-remanent component in ferroelectric ceramics. For this, "remanent hysteresis task" and "positive-up-negative-down technique" were performed which utilized the switchable properties of polarizations to nullify the contributions from the non-remanent (non-switchable) components. The report also addresses the time-dependent leakage behavior of the ceramics focusing on the presence of resistive leakage (a time-dependent parameter) present in the ceramics. The techniques presented here are especially useful for polycrystalline ceramics where leakage current leads to an erroneous estimation of Pr.

  4. Advanced Ceramics

    International Nuclear Information System (INIS)

    1989-01-01

    The First Florida-Brazil Seminar on Materials and the Second State Meeting about new materials in Rio de Janeiro State show the specific technical contribution in advanced ceramic sector. The others main topics discussed for the development of the country are the advanced ceramic programs the market, the national technic-scientific capacitation, the advanced ceramic patents, etc. (C.G.C.) [pt

  5. Corrosion resistant coatings for SiC and Si{sub 3}N{sub 4} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen Thierry; Shaokai Yang; J.J. Brown

    1998-09-01

    It is the goal of this program to (1) develop coatings for SiC and Si{sub 3}N{sub 4} that will enhance their performance as heat exchangers under coal combustion conditions and (2) to conduct an in-depth evaluation of the cause and severity of ceramic heat exchanger deterioration and failure under coal combustion conditions.

  6. Ceramic cutting tools materials, development and performance

    CERN Document Server

    Whitney, E Dow

    1994-01-01

    Interest in ceramics as a high speed cutting tool material is based primarily on favorable material properties. As a class of materials, ceramics possess high melting points, excellent hardness and good wear resistance. Unlike most metals, hardness levels in ceramics generally remain high at elevated temperatures which means that cutting tip integrity is relatively unaffected at high cutting speeds. Ceramics are also chemically inert against most workmetals.

  7. Structure refinement of (Sr,Ba)Nb2O6 ceramic powder from neutron and X-Ray diffraction data

    International Nuclear Information System (INIS)

    Carrio, J.G.; Mascarenhas, Y.P.; Yelon, W.; Santos, I.A.; Garcia, D.; Eiras, J.A.

    2002-01-01

    The structure of polycrystalline strontium barium niobate at room temperature was refined by the Rietveld method. Sintered ceramic samples were used to collect powder neutron and X-ray diffraction data. The ratio Sr/Ba ∼ 64/36 was found from the initial batch composition Sr 0 .61 Ba 0.39 Nb 2 O 6 , corroborating with the quantitative X-ray dispersive spectroscopy (EDS) measurements. The structure is tetragonal with cell parameters a, b 12.4504(3) Angstrom and c = 3.9325(1) Angstrom and space group P4bm. It was not necessary to introduce any positional disorder for the oxygen atoms. Cation Nb +5 displacements not parallel to the c direction are presented, which can influence the behavior of the ferroelectric properties. (author)

  8. Structure Refinement of (Sr,BaNb2O6 Ceramic Powder from Neutron and X-Rays Diffraction Data

    Directory of Open Access Journals (Sweden)

    J.G. Carrio

    2002-03-01

    Full Text Available The structure of polycrystalline strontium barium niobate at room temperature was refined by the Rietveld method. Sintered ceramic samples were used to collect powder neutron and X-ray diffraction data. The ratio Sr/Ba ~ 64/36 was found from the initial batch composition Sr0.61Ba0.39Nb2O6, corroborating with the quantitative X-ray dispersive spectroscopy (EDS measurements. The structure is tetragonal with cell parameters a, b = 12.4504(3 Å and c = 3.9325(1 Å and space group P4bm. It was not necessary to introduce any positional disorder for the oxygen atoms. Cation Nb+5 displacements not parallel to the c direction are presented, which can influence the behavior of the ferroelectric properties.

  9. Simulation of capillary infiltration into packing structures for the optimization of ceramic materials using the lattice Boltzmann method

    Directory of Open Access Journals (Sweden)

    Danilo Sergi

    2016-01-01

    Full Text Available This study uses the lattice Boltzmann method (LBM to simulate in 2D the capillary infiltration into porous structures obtained from the packing of particles. The experimental problem motivating the work is the densification of carbon preforms by reactive melt infiltration. The aim is to determine the optimization principles for the manufacturing of high-performance ceramics. Simulations are performed for packings with varying structural properties. The results suggest that the observed slow infiltrations can be ascribed to interface dynamics. Pinning represents the primary factor retarding fluid penetration. The mechanism responsible for this phenomenon is analyzed in detail. When surface growth is allowed, it is found that the phenomenon of pinning becomes stronger. Systems trying to reproduce typical experimental conditions are also investigated. It turns out that the standard for accurate simulations is challenging. The primary obstacle to overcome for enhanced accuracy seems to be the over-occurrence of pinning.

  10. Structural, electric and dielectric properties of Eu-doped SrBi2Nb2O9 ceramics obtained by co-precipitation route

    Directory of Open Access Journals (Sweden)

    Mohamed Afqir

    2018-03-01

    Full Text Available This paper presents a study of the structure and dielectric properties of Eu-doped SrBi2Nb2O9 ceramics prepared by co-precipitation route and sintered at 850 °C. The materials were examined using XRD and FTIR methods. XRD data indicated the formation of well crystallized structure of the pure and doped SrBi2Nb2O9, without the presence of undesirable phases. FTIR spectra do not bring a significant shift in the band positions. Moreover, the AC conductivity, dielectric constant and dielectric loss of the ceramics were determined through the frequency range [50 kHz–1 MHz]. In particular, the dielectric constant (ε′ and dielectric losses (tan δ of the SrBi2Nb2O9 and SrBi1.6Eu0.4Nb2O9 ceramics were measured as a function of temperature at various frequencies.

  11. A review of the strength properties of dental ceramics.

    Science.gov (United States)

    Hondrum, S O

    1992-06-01

    New ceramic materials for restorative dentistry have been developed and introduced in recent years. This article reviews advantages and disadvantages of dental ceramics, concentrating on strength properties. Included are factors affecting the strength of dental ceramic materials and the most common mechanisms for increasing the strength of dental ceramics. The properties of presently available materials such as dispersion-strengthened ceramics, cast ceramics, and foil-reinforced materials are discussed. Current research efforts to improve the fracture resistance of ceramic restorative materials are reviewed. A description of methods to evaluate the strength of ceramics is included, as a caution concerning the interpretation of strength data reported in the literature.

  12. Structural analysis of ceramic blocks sealing or structural incorporated with the industrial laundry sludge; Anllise estrutural de blocos ceramicos de vedacao ou estruturais incorporados com lodo de lavanderia industrial

    Energy Technology Data Exchange (ETDEWEB)

    Almeida, P.H.S.; Grippe, V.Y.Q.; Goulart, J.V., E-mail: phsoal@yahoo.com.br [Universidade Federal de Mato Grosso (UFMT), MT (Brazil)

    2016-07-01

    Industrial and commercial development of recent decades has led to an increase in waste generation. Thus, it is necessary to develop alternative and effective methods of treatment, replacing the simple disposal of these wastes in landfills. The objective of this work is to study the incorporation of textile industrial laundries sludge in ceramic blocks sealing or structural. Samples of ceramic blocks were produced using formulation with 20% sludge, the mass of ceramic clay. Structural analysis of the block was observed the tendency of most empty emergence (pores) during the firing of the blocks, as textile sludge was added in the ceramic paste composition. The mechanical testing of blocks compressive strength was above the minimum 3.0 MPa specified by the standard limit. The physical test water absorption of the blocks was within the range 8 to 22% specified by the standard. (author)

  13. Resistance to bond degradation between dual-cure resin cements and pre-treated sintered CAD-CAM dental ceramics.

    Science.gov (United States)

    Osorio, Raquel; Castillo-de Oyagüe, Raquel; Monticelli, Francesca; Osorio, Estrella; Toledano, Manuel

    2012-07-01

    To evaluate the bond stability of resin cements when luted to glass-reinforced alumina and zirconia CAD/CAM dental ceramics. Eighteen glass-infiltrated alumina and eighteen densely sintered zirconia blocks were randomly conditioned as follows: Group 1: No treatment; Group 2: Sandblasting (125 µm Al₂O₃-particles); and Group 3: Silica-coating (50 µm silica-modified Al₂O₃-particles). Composite samples were randomly bonded to the pretreated ceramic surfaces using different resin cements: Subgroup 1: Clearfil Esthetic Cement (CEC); Subgroup 2: RelyX Unicem (RXU); and Subgroup 3: Calibra (CAL). After 24 h, bonded specimens were cut into 1 ± 0.1 mm² sticks. One-half of the beams were tested for microtensile bond strength (MTBS). The remaining one-half was immersed in 10 % NaOCl aqueous solution (NaOClaq) for 5 h before testing. The fracture pattern and morphology of the debonded surfaces were assessed with a field emission gun scanning electron microscope (FEG-SEM). A multiple ANOVA was conducted to analyze the contributions of ceramic composition, surface treatment, resin cement type, and chemical challenging to MTBS. The Tukey test was run for multiple comparisons (p Resin-ceramic interfacial longevity depended on cement selection rather than on surface pre-treatments. The MDP-containing and the self-adhesive resin cements were both suitable for luting CAD/CAM ceramics. Despite both cements being prone to degradation, RXU luted to zirconia or untreated or sandblasted alumina showed the most stable interfaces. CAL experimented spontaneous debonding in all tested groups.

  14. Structural, topographical and electrical properties of cerium doped strontium barium niobate (Ce:SBN60) ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Raj, S. Gokul [Department of Physics, C. Kandaswami Naidu College For Men (CKNC), Annanagar, Chennai-600102 (India); Mathivanan, V.; Mohan, R. [Department of Physics, Presidency College, Chennai – 600005 (India); Kumar, G. Ramesh, E-mail: rameshvandhai@gmail.com; Yathavan, S. [Department of Physics, University College of Engineering Arni, Anna University Chennai, Arni-632317 (India)

    2016-05-06

    Tungsten bronze type cerium doped strontium barium niobate (Ce:SBN - Sr{sub 0.6}B{sub 0.4}Nb{sub 2}O{sub 6}) ceramics were synthesized by solid state process. Cerium was used as dopant to improve its electrical properties. Influence of Ce{sup +} ions on the photoluminescence properties was investigated in detail. The grain size topographical behavior of SBN powders and their associated abnormal grain growth (AGG) were completely analyzed through SEM studies. Finally dielectric, measurement discusses about the broad phase transition observed due to cerium dopant The results were discussed in detail.

  15. Structure degradation and conducting properties of the perovskite phase of yttrium ceramics

    CERN Document Server

    Kalanov, M U

    2002-01-01

    It is shown, that under normal conditions the perovskite phase of the yttrium ceramics of the [(Y,Ba)CuO sub 3 sub - subDELTA sub / sub 3] sub 3 is metastable and degrades in time. The degradation results in the YBa sub 2 Cu sub 3 O sub 7 sub - subdelta orthorhombic phase with transition into the superconducting state at T sub c = 91 K. The conductivity type changes thereby from the mixed metal-semiconductor character to the metallic one within the temperature interval of 100-300 K

  16. Structural Transition and Enhanced Ferromagnetic Properties of La, Nd, Gd, and Dy-Doped BiFeO3 Ceramics

    Science.gov (United States)

    Kumar, Ashwini; Varshney, Dinesh

    2015-11-01

    The structural, electrical, and magnetic properties of rare-earth-doped Bi0.8 RE0.2FeO3 ceramics (rare-earth (RE) = La, Nd, Gd, and Dy) synthesized by solid-state reaction are reported and discussed. The x-ray diffraction (XRD) patterns of Bi0.8La0.2FeO3 and Bi0.8Nd0.2FeO3 were indexed to rhombohedral ( R3 c) and triclinic ( P1) structures, respectively. Rietveld refinement of the XRD pattern of Bi0.8Dy0.2FeO3 confirmed its biphasic nature ( Pnma + R3 c space groups) whereas for Bi0.8Gd0.2FeO3 the orthorhombic phase with Pna21 symmetry made a major contribution, with minor contributions from the orthorhombic ( Pnma) and rhombohedral ( R3 c) phases. Raman spectroscopy revealed changes in BiFeO3 mode positions, in addition to structural changes, on RE ion substitution. The effect of RE ion substitution on dielectric constant and loss tangent were studied at room temperature in a wide range of frequency, 50 Hz-1 MHz. Room temperature magnetization-magnetic field ( M- H) measurements indicated that magnetization increased with increasing structural distortion and with partial destruction of the spin cycloid as a result of doping of BiFeO3 ceramics with rare earth ions. These compounds, with improved remnant magnetization and coercive field, are suitable for use in spin-based electronic devices.

  17. Composite Laser Ceramics by Advanced Bonding Technology.

    Science.gov (United States)

    Ikesue, Akio; Aung, Yan Lin; Kamimura, Tomosumi; Honda, Sawao; Iwamoto, Yuji

    2018-02-09

    Composites obtained by bonding materials with the same crystal structure and different chemical compositions can create new functions that do not exist in conventional concepts. We have succeeded in bonding polycrystalline YAG and Nd:YAG ceramics without any interstices at the bonding interface, and the bonding state of this composite was at the atomic level, similar to the grain boundary structure in ceramics. The mechanical strength of the bonded composite reached 278 MPa, which was not less than the strength of each host material (269 and 255 MPa). Thermal conductivity of the composite was 12.3 W/mK (theoretical value) which is intermediate between the thermal conductivities of YAG and Nd:YAG (14.1 and 10.2 W/mK, respectively). Light scattering cannot be detected at the bonding interface of the ceramic composite by laser tomography. Since the scattering coefficients of the monolithic material and the composite material formed by bonding up to 15 layers of the same materials were both 0.10%/cm, there was no occurrence of light scattering due to the bonding. In addition, it was not detected that the optical distortion and non-uniformity of the refractive index variation were caused by the bonding. An excitation light source (LD = 808 nm) was collimated to 200 μm and irradiated into a commercial 1% Nd:YAG single crystal, but fracture damage occurred at a low damage threshold of 80 kW/cm². On the other hand, the same test was conducted on the bonded interface of 1% Nd:YAG-YAG composite ceramics fabricated in this study, but it was not damaged until the excitation density reached 127 kW/cm². 0.6% Nd:YAG-YAG composite ceramics showed high damage resistance (up to 223 kW/cm²). It was concluded that composites formed by bonding polycrystalline ceramics are ideal in terms of thermo-mechanical and optical properties.

  18. The use of nanoparticles in polymeric and ceramic membrane structures: Review of manufacturing procedures and performance improvement for water treatment

    International Nuclear Information System (INIS)

    Kim, Jeonghwan; Van der Bruggen, Bart

    2010-01-01

    Membrane separations are powerful tools for various applications, including wastewater treatment and the removal of contaminants from drinking water. The performance of membranes is mainly limited by material properties. Recently, successful attempts have been made to add nanoparticles or nanotubes to polymers in membrane synthesis, with particle sizes ranging from 4 nm up to 100 nm. Ceramic membranes have been fabricated with catalytic nanoparticles for synergistic effects on the membrane performance. Breakthrough effects that have been reported in the field of water and wastewater treatment include fouling mitigation, improvement of permeate quality and flux enhancement. Nanomaterials that have been used include titania, alumina, silica, silver and many others. This paper reviews the role of engineered nanomaterials in (pressure driven) membrane technology for water treatment, to be applied in drinking water production and wastewater recycling. Benefits and drawbacks are described, which should be taken into account in further studies on potential risks related to release of nanoparticles into the environment. - Nanoparticles show a great potential for application in polymeric and ceramic membrane structures, in view of fouling mitigation and catalytic breakdown processes.

  19. Metals and Ceramics Division Materials Science Program. Annual progress report for period ending June 30, 1984

    Energy Technology Data Exchange (ETDEWEB)

    McHargue, C.J. (comp.)

    1984-11-01

    This report summarizes the activities of the Materials Sciences Program in the Metals and Ceramics Division for the period January 1, 1983, to June 30, 1984. These activities constitute about one-fourth of the research and development conducted by the division. The emphasis of the program can be described as the scientific design of materials. The efforts are directed toward three classes of materials: high-temperature metallic alloys based on intermetallic compounds, structural ceramics, and radiation-resistant alloys.

  20. Metals and Ceramics Division Materials Science Program. Annual progress report for period ending June 30, 1984

    International Nuclear Information System (INIS)

    McHargue, C.J.

    1984-11-01

    This report summarizes the activities of the Materials Sciences Program in the Metals and Ceramics Division for the period January 1, 1983, to June 30, 1984. These activities constitute about one-fourth of the research and development conducted by the division. The emphasis of the program can be described as the scientific design of materials. The efforts are directed toward three classes of materials: high-temperature metallic alloys based on intermetallic compounds, structural ceramics, and radiation-resistant alloys

  1. Control of vortex-induced non-resonance vibration using piezo-ceramic actuators embedded in a structure

    Science.gov (United States)

    Zhang, M. M.; Cheng, L.; Zhou, Y.

    2005-12-01

    Closed-loop control of vortex-induced non-resonant vibration of a flexible square cylinder is experimentally investigated in this paper. Piezo-ceramic actuators were embedded inside the cylinder to cause an oscillation of the cylinder surface, which subsequently altered the fluid-structure interaction. Experiments were conducted in a wind tunnel at Reynolds numbers, Re, of 2800 and 8000. Two typical control schemes, i.e. Y_control and u+Y_control, were deployed using feedback signals from structural vibration Y and combined Y and fluctuating flow velocity u, respectively. The control effects on the structural vibration and flow were assessed using a laser vibrometer, an optical fiber Bragg grating sensor, hot wires and particle image velocimetry. Experimental results show that both vortex shedding from the cylinder and the vortex-induced non-resonant vibration were effectively suppressed. The best control effects were observed with u+Y_control in use; the root mean square values of Y, the structural strain rate ɛy along the lift direction and u, i.e. Yrms, ɛy,rms and urms, and the circulation Γ dropped at Re = 8000 by 58%, 52%, 53% and 88%, respectively, compared with the unperturbed case. It was found that the control effectively modified the nature of the fluid-structure interaction by changing the in-phase fluid-structure synchronization at all dominant frequencies into anti-phase interaction, accounting for the suppression in both vortex shedding and structural vibration.

  2. Microwave-assisted sintering of non-stoichiometric strontium bismuth niobate ceramic: Structural and dielectric properties

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Rajveer [Department of Physics and Astrophysics, University of Delhi, New Delhi 110007 (India); Department of Physics, Atmaram Sanatan Dharma College, University of Delhi, Dhaula Kuan, New Delhi 110021 (India); Luthra, Vandna [Department of Physics, Gargi College, University of Delhi, Siri Fort Road, New Delhi 110049 (India); Tandon, R.P., E-mail: ram_tandon@hotmail.com [Department of Physics and Astrophysics, University of Delhi, New Delhi 110007 (India)

    2016-11-01

    In recent years the microwave sintering has been utilized for the synthesis of materials in enhancement of the properties. In this paper strontium bismuth niobate (Sr{sub 0.8}Bi{sub 2.2}Nb{sub 2}O{sub 9}:SBN) bulk ceramic has been synthesized by microwave reactive sintering and conventional heating techniques. A relative density of 99.6% has been achieved for microwave sintered SBN, which is higher than that of (98.81%) conventionally sintered SBN. The phase formation of SBN synthesized by both processes has been confirmed by X-ray diffraction (XRD). The surface morphology of SBN was observed by scanning electron microscopy (SEM). The microstructure was found to be more uniform in case of SBN sintered by microwave sintering. The dielectric properties of SBN were studied as a function of frequency in the temperature range of 30–500 °C. Both the samples synthesized by two different processes were found to follow Curie–Weiss law above the transition temperature. The Curie temperature was found to be higher for microwave sintered SBN. The dielectric constant and the transition temperature were observed to be higher for SBN ceramic synthesized by microwave sintering technique. The ac and dc activation energy values were also found to be higher for microwave sintered SBN as compared to conventional sintering technique.

  3. Correlation between structural, electrical and magnetic properties of GdMnO3 bulk ceramics

    International Nuclear Information System (INIS)

    Samantaray, S.; Mishra, D.K.; Pradhan, S.K.; Mishra, P.; Sekhar, B.R.; Behera, Debdhyan; Rout, P.P.; Das, S.K.; Sahu, D.R.; Roul, B.K.

    2013-01-01

    This paper reports the effect of sintering temperature on ferroelectric properties of GdMnO 3 (GMO) bulk ceramics at room temperature prepared by the conventional solid state reaction route following slow step sintering schedule. Ferroelectric hysteresis loop as well as sharp dielectric anomaly in pure (99.999%) GMO sintered ceramics has been clearly observed. Samples sintered at 1350 °C become orthorhombic with Pbnm space group and showed frequency independent sharp dielectric anomalies at 373 K and a square type of novel ferroelectric hysteresis loop was observed at room temperature. Interestingly, dielectric anomalies and ferroelectric behavior were observed to be dependent upon sintering temperature of GdMnO 3 . Room temperature dielectric constant (ε r ) value at different frequencies is observed to be abnormally high. The magnetic field and temperature dependent magnetization show antiferromagnetic behavior at 40 K for both 1350 °C and 1700 °C sintered GMO. Present findings showed the possibility of application of GdMnO 3 at room temperature as multifunctional materials. - Highlights: • Preparation of single-phasic polycrystalline GdMnO 3 sample by the solid state sintering route. • Observation of square type P–E hysteresis loop with higher saturation and remnant polarization. • Observation of antiferromagnetic behavior at 40 K in polycrystalline GdMnO 3 . • Possibility of room temperature application of GdMnO 3 as multifunctional material

  4. Correlation between structural, electrical and magnetic properties of GdMnO3 bulk ceramics

    Science.gov (United States)

    Samantaray, S.; Mishra, D. K.; Pradhan, S. K.; Mishra, P.; Sekhar, B. R.; Behera, Debdhyan; Rout, P. P.; Das, S. K.; Sahu, D. R.; Roul, B. K.

    2013-08-01

    This paper reports the effect of sintering temperature on ferroelectric properties of GdMnO3 (GMO) bulk ceramics at room temperature prepared by the conventional solid state reaction route following slow step sintering schedule. Ferroelectric hysteresis loop as well as sharp dielectric anomaly in pure (99.999%) GMO sintered ceramics has been clearly observed. Samples sintered at 1350 °C become orthorhombic with Pbnm space group and showed frequency independent sharp dielectric anomalies at 373 K and a square type of novel ferroelectric hysteresis loop was observed at room temperature. Interestingly, dielectric anomalies and ferroelectric behavior were observed to be dependent upon sintering temperature of GdMnO3. Room temperature dielectric constant (ɛr) value at different frequencies is observed to be abnormally high. The magnetic field and temperature dependent magnetization show antiferromagnetic behavior at 40 K for both 1350 °C and 1700 °C sintered GMO. Present findings showed the possibility of application of GdMnO3 at room temperature as multifunctional materials.

  5. Correlation between structural, electrical and magnetic properties of GdMnO{sub 3} bulk ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Samantaray, S. [Institute of Materials Science, Planetarium Building, Bhubaneswar 751013, Odisha (India); Mishra, D.K. [Department of Physics, Institute of Technical Education and Research, S ‘O’ A University, Bhubaneswar 751030, Odisha (India); Pradhan, S.K. [Institute of Materials Science, Planetarium Building, Bhubaneswar 751013, Odisha (India); Mishra, P.; Sekhar, B.R. [Institue of Physics, Sachivalaya Marg, Bhubaneswar, Odisha (India); Behera, Debdhyan [Advanced Materials Technology Department, CSIR-Institute of Minerals and Materials Technology, Bhubaneswar 751013, Odisha (India); Rout, P.P.; Das, S.K. [Institute of Materials Science, Planetarium Building, Bhubaneswar 751013, Odisha (India); Sahu, D.R. [School of Physics, University of the Witwatersrand, Johannesburg (South Africa); Roul, B.K., E-mail: ims@iopb.res.in [Institute of Materials Science, Planetarium Building, Bhubaneswar 751013, Odisha (India)

    2013-08-15

    This paper reports the effect of sintering temperature on ferroelectric properties of GdMnO{sub 3} (GMO) bulk ceramics at room temperature prepared by the conventional solid state reaction route following slow step sintering schedule. Ferroelectric hysteresis loop as well as sharp dielectric anomaly in pure (99.999%) GMO sintered ceramics has been clearly observed. Samples sintered at 1350 °C become orthorhombic with Pbnm space group and showed frequency independent sharp dielectric anomalies at 373 K and a square type of novel ferroelectric hysteresis loop was observed at room temperature. Interestingly, dielectric anomalies and ferroelectric behavior were observed to be dependent upon sintering temperature of GdMnO{sub 3}. Room temperature dielectric constant (ε{sub r}) value at different frequencies is observed to be abnormally high. The magnetic field and temperature dependent magnetization show antiferromagnetic behavior at 40 K for both 1350 °C and 1700 °C sintered GMO. Present findings showed the possibility of application of GdMnO{sub 3} at room temperature as multifunctional materials. - Highlights: • Preparation of single-phasic polycrystalline GdMnO{sub 3} sample by the solid state sintering route. • Observation of square type P–E hysteresis loop with higher saturation and remnant polarization. • Observation of antiferromagnetic behavior at 40 K in polycrystalline GdMnO{sub 3}. • Possibility of room temperature application of GdMnO{sub 3} as multifunctional material.

  6. Glycerin purification using asymmetric nano-structured ceramic membranes from production of waste fish oil biodiesel

    Science.gov (United States)

    Maghami, M.; Sadrameli, S. M.; Shamloo, M.

    2018-02-01

    Biodiesel is an environmental friendly alternative liquid transportation fuel that can be used in diesel engines without major modifications. The scope of this research work is to produce biodiesel from waste fish oil and its purification from the byproducts using a ceramic membrane. Transesterification of waste fish oil was applied for the biodiesel production using methanol in the presence of KOH as a catalyst. Effect of catalyst weight percent, temperature and methanol to oil molar ratio (MR) on the biodiesel yield have been studied and the results show that highest methyl ester yield of 79.2% has been obtained at 60 °C, MR: 6 and 1% KOH. The produced biodiesel purified by a ceramic membrane. Membrane flux and glycerin removal at different operating conditions such as temperature, trans-membrane pressures and cross flow velocities have been measured. Glycerin purity by membrane method is 99.97% by weight at the optimum condition. The highest membrane flux occurred at 50 °C temperature, 1 bar pressure and 3 m/s velocity.

  7. Inferring the interaction structure of resistance to antimicrobials.

    Science.gov (United States)

    Zawack, Kelson; Love, Will; Lanzas, Cristina; Booth, James G; Gröhn, Yrjö T

    2018-04-01

    The growth of antimicrobial resistance presents a significant threat to human and animal health. Of particular concern is multi-drug resistance, as this increases the chances an infection will be untreatable by any antibiotic. In order to understand multi-drug resistance, it is essential to understand the association between drug resistances. Pairwise associations characterize the connectivity between resistances and are useful in making decisions about courses of treatment, or the design of drug cocktails. Higher-order associations, interactions, which tie together groups of drugs can suggest commonalities in resistance mechanism and lead to their identification. To capture interactions, we apply log-linear models of contingency tables to analyze publically available data on the resistance of Escheresia coli isolated from chicken and turkey meat by the National Antimicrobial Resistance Monitoring System. Standard large sample and conditional exact testing approaches for assessing significance of parameters in these models breakdown due to structured patterns inherent to antimicrobial resistance. To address this, we adopt a Bayesian approach which reveals that E. coli resistance associations can be broken into two subnetworks. The first subnetwork is characterized by a hierarchy of β-lactams which is consistent across the chicken and turkey datasets. Tier one in this hierarchy is a near equivalency between amoxicillin-clavulanic acid, ceftriaxone and cefoxitin. Susceptibility to tier one then implies susceptibility to ceftiofur. The second subnetwork is characterized by more complex interactions between a variety of drug classes that vary between the chicken and turkey datasets. Copyright © 2018 Elsevier B.V. All rights reserved.

  8. Structural relaxation in the magnetically treated glass ceramic Bi1.8Pb0.2Sr2CaCu2Ox

    International Nuclear Information System (INIS)

    Alekseenko, V.I.; Volkova, G.K.; Konstanminova, T.E.; Nosolev, I.K.; Popova, I.B.

    1994-01-01

    Structure relaxation in Bi 1.8 Pb 0.2 Sr 2 CaCu 2 O x amorphous glass ceramics after the treatment using weak pulse magnetic field is studied using microindentation, X-ray structure analysis and inner friction techniques. Structure relaxation after substance treatment using pulse magnetic field is detected to occur at room temperature and to result in its strengthening (increase of microhardness-H v ) and in reduction of inner microstress level.9 refs., 4 figs

  9. Effects of (LiCe) co-substitution on the structural and electrical properties of CaBi2Nb2O9 ceramics

    Science.gov (United States)

    Tian, Xiao-Xia; Qu, Shao-Bo; Du, Hong-Liang; Li, Ye; Xu, Zhuo

    2012-03-01

    The piezoelectric, dielectric, and ferroelectric properties of the (LiCe) co-substituted calcium bismuth niobate (CaBi2Nb2O9, CBNO) are investigated. The piezoelectric properties of CBNO ceramics are significantly enhanced and the dielectric loss tan δ decreased. This makes poling using (LiCe) co-substitution easier. The ceramics (where □ represents A-site Ca2+ vacancies, possess a pure layered structure phase and no other phases can be found. The Ca0.88(LiCe)0.04□0.04Bi2Nb2O9 ceramics possess optimal piezoelectric properties, with piezoelectric coefficient (d33) and Curie temperature (TC) found to be 13.3 pC/N and 960 °C, respectively. The dielectric and piezoelectric properties of the (LiCe) co-substituted CBNO ceramics exhibit very stable temperature behaviours. This demonstrates that the CBNO ceramics are a promising candidate for ultrahigh temperature applications.

  10. Structural characterization of advanced ceramics using the neutron diffractometer developed by Instituto de Pesquisas Energeticas e Nucleares (IPEN)

    International Nuclear Information System (INIS)

    Parente, C.B.R.; Mazzocchi, V.L.

    1999-01-01

    Application of neutron diffractometer at the Instituto de Pesquisas Energeticas Nucleares, Sao Paulo, Brazil, in the structural investigations of advanced ceramics was presented. Methodology of the analysis of neutron diffraction patterns was tested with BaLiF 3 single crystals and also doped with Ni 2+ or Pb 2+ ions. The same methodology was used to investigate the HTSC phases in the system Bi-Sr-Ca-Cu-O. The system Bi 1.7 Pb 0.3 Sr 2 Ca 2.2 Cu 3.5 O 10.6 was also investigated. Addition of Pb 2+ ions increased the fraction of high-T c phase 2223. Symmetry in neutron multiple diffraction patterns, obtained for aluminium single crystal, was elaborated. Crystal lattice parameter for aluminium single crystal was determined at different temperatures using neutron multiple diffraction. (author)

  11. Mechanical behavior analysis of small-scale modeling of ceramic block masonry structures: geometries effect

    Directory of Open Access Journals (Sweden)

    E. Rizzatti

    Full Text Available This paper presents the experimental results of a research program with ceramic block masonry under compression. Four different block geometries were investigated. Two of them had circular hollows with different net area. The third one had two rectangular hollow and the last block was with rectangular hollows and a double central webs. The prisms and walls were built with two mortar type 1:1:6 (I and 1:0,5:4 (II (proportions by volume of cement: lime: sand. One:three small scale blocks were used to test block, prisms and walls on compression. It was possible to conclude that the block with double central webs gave better results of compressive strength showing to be more efficient. The mortar didn't influenced the compressive strength of prisms and walls.

  12. Structural analysis of Fe-Mn-O nanoparticles in glass ceramics by small angle scattering

    Science.gov (United States)

    Raghuwanshi, Vikram Singh; Harizanova, Ruzha; Tatchev, Dragomir; Hoell, Armin; Rüssel, Christian

    2015-02-01

    Magnetic nanocrystals containing Fe and Mn were obtained by annealing of silicate glasses with the composition 13.6Na2O-62.9SiO2-8.5MnO-15.0Fe2O3-x (mol%) at 580 °C for different periods of time. Here, we present Small Angle Neutron Scattering using Polarized neutrons (SANSPOL) and Anomalous Small Angle X-ray Scattering (ASAXS) investigation on these glass ceramic samples. Analysis of scattering data from both methods reveals the formation of spherical core-shell type of nanoparticles with mean sizes between 10 nm and 100 nm. ASAXS investigation shows the particles have higher concentration of iron atoms and the shell like region surrounding the particles is enriched in SiO2. SANSPOL investigation shows the particles are found to be magnetic and are surrounded by a non-magnetic shell-like region.

  13. Positron annihilation in transparent ceramics

    International Nuclear Information System (INIS)

    Husband, P; Selim, F A; Bartošová, I; Slugeň, V

    2016-01-01

    Transparent ceramics are emerging as excellent candidates for many photonic applications including laser, scintillation and illumination. However achieving perfect transparency is essential in these applications and requires high technology processing and complete understanding for the ceramic microstructure and its effect on the optical properties. Positron annihilation spectroscopy (PAS) is the perfect tool to study porosity and defects. It has been applied to investigate many ceramic structures; and transparent ceramics field may be greatly advanced by applying PAS. In this work positron lifetime (PLT) measurements were carried out in parallel with optical studies on yttrium aluminum garnet transparent ceramics in order to gain an understanding for their structure at the atomic level and its effect on the transparency and light scattering. The study confirmed that PAS can provide useful information on their microstructure and guide the technology of manufacturing and advancing transparent ceramics. (paper)

  14. Proceedings of the Office of Fusion Energy/DOE workshop on ceramic matrix composites for structural applications in fusion reactors

    International Nuclear Information System (INIS)

    Jones, R.H.; Lucas, G.E.

    1990-11-01

    A workshop to assess the potential application of ceramic matrix composites (CMCs) for structural applications in fusion reactors was held on May 21--22, 1990, at University of California, Santa Barbara. Participants included individuals familiar with materials and design requirements in fusion reactors, ceramic composite processing and properties and radiation effects. The primary focus was to list the feasibility issues that might limit the application of these materials in fusion reactors. Clear advantages for the use of CMCs are high-temperature operation, which would allow a high-efficiency Rankine cycle, and low activation. Limitations to their use are material costs, fabrication complexity and costs, lack of familiarity with these materials in design, and the lack of data on radiation stability at relevant temperatures and fluences. Fusion-relevant feasibility issues identified at this workshop include: hermetic and vacuum properties related to effects of matrix porosity and matrix microcracking; chemical compatibility with coolant, tritium, and breeder and multiplier materials, radiation effects on compatibility; radiation stability and integrity; and ability to join CMCs in the shop and at the reactor site, radiation stability and integrity of joints. A summary of ongoing CMC radiation programs is also given. It was suggested that a true feasibility assessment of CMCs for fusion structural applications could not be completed without evaluation of a material ''tailored'' to fusion conditions or at least to radiation stability. It was suggested that a follow-up workshop be held to design a tailored composite after the results of CMC radiation studies are available and the critical feasibility issues are addressed

  15. Synthesis, Structural and Morphological Property of BaSnO3 Nanopowder Prepared by Solid State Ceramic Method

    Science.gov (United States)

    John, Jibi; Mahadevan Pillai, V. P.; Thomas, Anitta Rose; Philip, Reji; Joseph, Jaison; Muthunatesan, S.; Ragavendran, V.; Prabhu, Radhakrishna

    2017-05-01

    BaSnO3 is a cubic perovskite-type oxide that behaves as an n-type semiconductor with a wide band gap of 3.4 eV and remains stable at temperatures up to 1000°C. It has wide applications such as thermally stable capacitors, humidity sensors, gas sensors, etc. Barium stannate has also been used in optical applications, in capacitors and ceramic boundary layers, and as a promising material to produce gas phase sensors for the detection of carbon monoxide and carbon dioxide. BaSnO3 powder was prepared by solid state ceramic method. X-ray diffraction pattern of the prepared sample presents all the characteristic peaks of cubic phase of BaSnO3 (JCPDScard no: 15 -0780). The lattice constant for the compound was calculated and found to be 4.101A0 which is in agreement with the reported value (4.112A0). The average size of the crystallites estimated by Debye Scherrer’s formula was found to be 49 nm shows the nanostructured nature. The Raman bands observed ~ 139, 833 and 1122 cm-1 can be assigned on the basis of the fundamental vibrations of SnO6 octahedron which has Oh symmetry, in the distorted perovskite structure. The SEM image shows a porous surface morphology with grains of cuboidal structure with well-defined grain boundaries. UV-Visible spectra shows BaSnO3powder exhibit high reflectance in the 400-700 nm range.

  16. Structure and transport properties of La1−x Srx MnO3 granular ceramics

    International Nuclear Information System (INIS)

    Jirák, Zdeněk; Hirschner, Jan; Kaman, Ondřej; Knížek, Karel; Levinský, Petr; Maryško, Miroslav; Hejtmánek, Jiří

    2017-01-01

    Two granular ceramics were prepared by spark plasma sintering (SPS) at 600–800 °C and classical ceramic sintering (CCS) at 900 °C using molten salt synthesized nanoparticles of the composition La 0.53 Sr 0.47 MnO 3 and  ≈40 nm size. Extensive study of the structural, magnetic, and electric transport properties showed that the SPS and CCS products essentially retain the two-phase magnetic structure of the starting nanoparticles, which consist of a ferromagnetic (FM) core and an A -type antiferromagnetic (AFM) shell. After the sintering, the AFM phase forms a 10–15 nm thick spacer between neighbouring FM granules, which represents a barrier for the transmission of spin-polarized e g carriers. This assembly retains reasonable conductivity down to the lowest temperatures, without marked localization, and it still gives rise to a large negative magnetoresistance, which is treated theoretically in terms of low- and high-field positive magnetoconductance. In a detailed analysis of these low-field magnetoconductance (LFMC) and high-field magnetoconductance (HFMC) effects, which are related to the field-induced alignment of the FM granules and spin canting in the AFM matrix, respectively, we conclude that the bulk conductivity is governed by resonant tunnelling, i.e. the second-order transmission via Mn 4+ sites in the intergranular space. The experimental data on the SPS product confirm the theoretically predicted scaling of the LFMC effect with squared reduced magnetization, and also provide also a quantitative comparison between the linear coefficient of the HFMC and the high-field paraprocess seen in the magnetization measurement. (paper)

  17. Evaluation of the Moldboard Structure Resistance of the Grader Equipment

    Directory of Open Access Journals (Sweden)

    Carmen Debeleac

    2013-09-01

    Full Text Available In this paper, the author presents a method for evaluation of the moldboard structure resistance of the motor-graders. Usual grader model was chosen to be analyzed by the FEM. Horizontal force of the blade was estimated using the classical soil mechanics theories for cutting soil proposed by McKyes. The simulation results can be useful for structural performance evaluation of these machine used in construction and agricultural fields.

  18. Fracture Resistance, Surface Defects and Structural Strength of Glass

    NARCIS (Netherlands)

    Rodichev, Y.M.; Veer, F.A.

    2010-01-01

    This paper poses the theory that the fracture resistance of basic float glass is dependent on it physicochemical properties and the surface defects fonned under the float glass production, glass processing and handling at the service conditions compose the aggregate basis for structural glass

  19. Using graphene networks to build bioinspired self-monitoring ceramics

    Science.gov (United States)

    Picot, Olivier T.; Rocha, Victoria G.; Ferraro, Claudio; Ni, Na; D'Elia, Eleonora; Meille, Sylvain; Chevalier, Jerome; Saunders, Theo; Peijs, Ton; Reece, Mike J.; Saiz, Eduardo

    2017-01-01

    The properties of graphene open new opportunities for the fabrication of composites exhibiting unique structural and functional capabilities. However, to achieve this goal we should build materials with carefully designed architectures. Here, we describe the fabrication of ceramic-graphene composites by combining graphene foams with pre-ceramic polymers and spark plasma sintering. The result is a material containing an interconnected, microscopic network of very thin (20–30 nm), electrically conductive, carbon interfaces. This network generates electrical conductivities up to two orders of magnitude higher than those of other ceramics with similar graphene or carbon nanotube contents and can be used to monitor ‘in situ' structural integrity. In addition, it directs crack propagation, promoting stable crack growth and increasing the fracture resistance by an order of magnitude. These results demonstrate that the rational integration of nanomaterials could be a fruitful path towards building composites combining unique mechanical and functional performances. PMID:28181518

  20. Flyweight, Superelastic, Electrically Conductive, and Flame-Retardant 3D Multi-Nanolayer Graphene/Ceramic Metamaterial.

    Science.gov (United States)

    Zhang, Qiangqiang; Lin, Dong; Deng, Biwei; Xu, Xiang; Nian, Qiong; Jin, Shengyu; Leedy, Kevin D; Li, Hui; Cheng, Gary J

    2017-07-01

    A ceramic/graphene metamaterial (GCM) with microstructure-derived superelasticity and structural robustness is achieved by designing hierarchical honeycomb microstructures, which are composited with two brittle constituents (graphene and ceramic) assembled in multi-nanolayer cellular walls. Attributed to the designed microstructure, well-interconnected scaffolds, chemically bonded interface, and coupled strengthening effect between the graphene framework and the nanolayers of the Al 2 O 3 ceramic (NAC), the GCM demonstrates a sequence of multifunctional properties simultaneously that have not been reported for ceramics and ceramics-matrix-composite structures, such as flyweight density, 80% reversible compressibility, high fatigue resistance, high electrical conductivity, and excellent thermal-insulation/flame-retardant performance simultaneously. The 3D well-ordered graphene aerogel templates are strongly coupled with the NAC by the chemically bonded interface, exhibiting mutual strengthening, compatible deformability, and a linearly dependent relationship between the density and Young's modulus. Considerable size effects of the ceramic nanolayers on the mechanical properties are revealed in these ceramic-based metamaterials. The designed hierarchical honeycomb graphene with a fourth dimensional control of the ceramic nanolayers on new ways to scalable fabrication of advanced multifunctional ceramic composites with controllable design suggest a great potential in applications of flexible conductors, shock/vibration absorbers, thermal shock barriers, thermal insulation/flame-retardant skins, and porous microwave-absorbing coatings. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. INVESTIGATION OF THERMAL BEHAVIOR OF MULTILAYERED FIRE RESISTANT STRUCTURE

    Directory of Open Access Journals (Sweden)

    R. GUOBYS

    2016-09-01

    Full Text Available This paper presents experimental and numerical investigations of thermal behavior under real fire conditions of new generation multilayered fire resistant structure (fire door, dimensions H × W × D: 2090 × 980 × 52 mm combining high strength and fire safety. This fire door consists of two steel sheets (thickness 1.5 and 0.7 mm with stone wool ( = 33 kg/m3, k = 0.037 W/mK, E = 5000 N/m2,  = 0.2 insulating layer in between. One surface of the structure was heated in fire furnace for specified period of time of 60 min. Temperature and deformation of opposite surface were measured from outside at selected measuring points during fire resistance test. Results are presented as temperature-time and thermal deformation-time graphs. Experimental results were compared with numerical temperature field simulation results obtained from SolidWorks®Simulation software. Numerical results were found to be in good agreement with experimental data. The percent differences between door temperatures from simulation and fire resistance test don’t exceed 8%. This shows that thermal behaviour of such multilayered structures can be investigated numerically, thus avoiding costly and time-consuming fire resistance tests. It is established that investigated structure should be installed in a way that places thicker steel sheet closer to the potential heat source than thinner one. It is also obtained that stone wool layer of higher density should be used to improve fire resistance of the structure.

  2. 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.

  3. Thermal shock and thermal fatigue resistant ZrO2/Al2O3 ceramics in the eutectic composition range. Pt. 1

    International Nuclear Information System (INIS)

    Liu, T.; Dorfschmidt, K.; Oberacker, R.

    1992-01-01

    Thermal shock and thermal fatigue resistant ZrO 2 /Al 2 O 3 ceramics in the eutectic composition range have been prepared and characterized in this work. The microstructures such as chemical composition (Al 2 O 3 -content), stabilizer (Y 2 O 3 , CeO 2 ), porosity, grain size and crack configuration (duplex, dendrite microstructure) have been varied systematically by different processing techniques. Mechanical properties such as Youngs modulus, bending strength, fracture toughness and R-curve behaviour have been investigated. Interrelations between the above microstructures and the mechanical properties have been established. Optimized combination of high toughness and high strength has been reached in crack free, fine-grained Ce-stabilized ZA-materials. On the other hand pronounced inelastic behaviour has been measured by optimization of the crack configuration in the duplex and dendrite microstructures. 6 refs., 1 tab., 10 figs

  4. Calcium-Magnesium-Alumino-Silicates (CMAS) Reaction Mechanisms and Resistance of Advanced Turbine Environmental Barrier Coatings for SiC/SiC Ceramic Matrix Composites

    Science.gov (United States)

    Zhu, Dongming; Costa, Gustavo; Harder, Bryan J.; Wiesner, Valerie L.; Hurst, Janet B.; Puleo, Bernadette J.

    2017-01-01

    Environmental barrier coatings (EBCs) and SiC/SiC ceramic matrix composites (CMCs) systems will play a crucial role in future turbine engines for hot-section component applications because of their ability to significantly increase engine operating temperatures, reduce engine weight and cooling requirements. The development of prime-reliant environmental barrier coatings is an essential requirement to enable the applications of the 2700-3000 F EBC - CMC systems. This presentation primarily focuses on the reaction mechanisms of advanced NASA environmental barrier coating systems, when in contact with Calcium-Magnesium Alumino-Silicates (CMAS) at high temperatures. Advanced oxide-silicate defect cluster environmental barrier coatings are being designed for ultimate balanced controls of the EBC temperature capability and CMAS reactivity, thus improving the CMAS resistance. Further CMAS mitigation strategies are also discussed.

  5. Electric-pulse-induced resistance switching effect in the bulk of La0.5Ca0.5MnO3 ceramics

    Directory of Open Access Journals (Sweden)

    M. L. Wu

    2014-04-01

    Full Text Available In the majority of contributions, the electrical–pulse-induced resistance (EPIR switching effect of perovskite manganites is thought to originate from the extrinsic interfacial Schottky barrier between the metal electrode and the surface of sample. In this work, La0.5Ca0.5MnO3 (LCMO ceramic samples were synthesized by solid state reaction and the transport properties, especially, the EPIR effect and memristor behavior were investigated under 4-wire method using silver-glue as electrodes. Although the I-V characteristic of LCMO shows an ohmic linearity under the 4-wire mode at room temperature, a stable and remarkable EPIR can still be observed when the pulse voltage is more than a critical value. This bulk EPIR effect is novel for rare - earth doped manganites.

  6. Structural origin of resistance drift in amorphous GeTe

    Science.gov (United States)

    Zipoli, Federico; Krebs, Daniel; Curioni, Alessandro

    2016-03-01

    We used atomistic simulations to study the origin of the change of resistance over time in the amorphous phase of GeTe, a prototypical phase-change material (PCM). Understanding the cause of resistance drift is one of the biggest challenges to improve multilevel storage technology. For this purpose, we generated amorphous structures via classical molecular-dynamics simulations under conditions as close as possible to the experimental operating ones of such memory devices. Moreover, we used the replica-exchange technique to generate structures comparable with those obtained in the experiment after long annealing that show an increase of resistance. This framework allowed us to overcome the main limitation of previous simulations, based on density-functional theory, that suffered from being computationally too expensive therefore limited to the nanosecond time scale. We found that resistance drift is caused by consumption of Ge atom clusters in which the coordination of at least one Ge atom differs from that of the crystalline phase and by removal of stretched bonds in the amorphous network, leading to a shift of the Fermi level towards the middle of the band gap. These results show that one route to design better memory devices based on current chalcogenide alloys is to reduce the resistance drift by increasing the rigidity of the amorphous network.

  7. Development of ceramics system many functions shielding materials

    International Nuclear Information System (INIS)

    Senda, Tetsuya; Akiyama, Shigeru; Takahashi, Chiori; Matsuoka, Kazuyoshi; Uematsu, Susumu; Ushijima, Michio; Ueki, Kotaro; Ohashi, Atsuto; Naruyama, Nobuteru

    1997-01-01

    To develop many functions shielding materials with optimum structure combined shielding with other functions, we studied neutron shielding function of ceramics system materials and thermo-resistant bombardment and thermo fatigue strength of ceramics and its complex materials in this fiscal year. Titanium borate (TiB 2 ) and boron nitride (BN) were investigated about neutron shielding performance, estimation of thermo fatigue strength and evaluation of joint strength. Combination of stainless steel (SUS304) and shielding materials was measured. When stainless steel with 25 cm thickness was set up, enhancement effects of TiB 2 and BN were observed. The strength of brazing part of ceramics/metal and ceramics/ceramics was measured. The obtained results showed the first fracture (mode I) was generated in the interface of materials with smaller linear expansion coefficient and brazing part. Results of laser thermal shock test of ceramics proved that the thermal shock fatigue limit laser power density P fc (W/mm 2 ) had tendency to converge the constant value with repeating laser irradiation. (S.Y.)

  8. Development of ceramics system many functions shielding materials

    Energy Technology Data Exchange (ETDEWEB)

    Senda, Tetsuya; Akiyama, Shigeru; Takahashi, Chiori; Matsuoka, Kazuyoshi; Uematsu, Susumu; Ushijima, Michio; Ueki, Kotaro; Ohashi, Atsuto; Naruyama, Nobuteru [Ship Research Inst., Mitaka, Tokyo (Japan)

    1997-02-01

    To develop many functions shielding materials with optimum structure combined shielding with other functions, we studied neutron shielding function of ceramics system materials and thermo-resistant bombardment and thermo fatigue strength of ceramics and its complex materials in this fiscal year. Titanium borate (TiB{sub 2}) and boron nitride (BN) were investigated about neutron shielding performance, estimation of thermo fatigue strength and evaluation of joint strength. Combination of stainless steel (SUS304) and shielding materials was measured. When stainless steel with 25 cm thickness was set up, enhancement effects of TiB{sub 2} and BN were observed. The strength of brazing part of ceramics/metal and ceramics/ceramics was measured. The obtained results showed the first fracture (mode I) was generated in the interface of materials with smaller linear expansion coefficient and brazing part. Results of laser thermal shock test of ceramics proved that the thermal shock fatigue limit laser power density P{sub fc} (W/mm{sup 2}) had tendency to converge the constant value with repeating laser irradiation. (S.Y.)

  9. Experimental and theoretical approaches for magnetic, superconducting and structural characterization of Bi1.75Pb0.25Sr2Ca2Cu3-xSnxO10+y glass ceramics

    Science.gov (United States)

    Koralay, Haluk; Cavdar, Sukru; Arslan, Aysun; Ozturk, Ozgur; Tasci, Ahmet Tolga; Tugluoglu, Nihat

    2017-12-01

    In this work, the effect of the partial substitution of Sn for Cu on structural, electrical and magnetic properties in the superconducting ceramic glass Bi1.75Pb0.25Sr2Ca2Cu3-xSnxO10+y system (x = 0, 0.1, 0.5) has been examined. The structural characterization of samples produced by glass-ceramic technique were done by X-ray diffraction (XRD) and scanning electron microscopy (SEM) measurements. The electrical and magnetic properties were determined by resistance-temperature (R-T) measurement and magnetization-magnetic field measurement (M-H) in the low temperature by using vibrating sample magnetometer (VSM), respectively. From the results of R-T measurement, the value of critical temperature (Tcoffset) has been decreased from 98 K to 73 K with increasing Sn- concentration. The critical current density has also been decreased with increasing magnetic field intensity. It has been observed from M-H plots that it was decreased with increasing the value of temperature. We have observed from M-H curves that the area size of the hysteresis curve decreases with increasing the value of temperature.

  10. Barley Stem Rust Resistance Genes: Structure and Function

    Directory of Open Access Journals (Sweden)

    Andris Kleinhofs

    2009-07-01

    Full Text Available Rusts are biotrophic pathogens that attack many plant species but are particularly destructive on cereal crops. The stem rusts (caused by have historically caused severe crop losses and continue to threaten production today. Barley ( L. breeders have controlled major stem rust epidemics since the 1940s with a single durable resistance gene . As new epidemics have threatened, additional resistance genes were identified to counter new rust races, such as the complex locus against races QCCJ and TTKSK. To understand how these genes work, we initiated research to clone and characterize them. The gene encodes a unique protein kinase with dual kinase domains, an active kinase, and a pseudokinase. Function of both domains is essential to confer resistance. The and genes are closely linked and function coordinately to confer resistance to several wheat ( L. stem rust races, including the race TTKSK (also called Ug99 that threatens the world's barley and wheat crops. The gene encodes typical resistance gene domains NBS, LRR, and protein kinase but is unique in that all three domains reside in a single gene, a previously unknown structure among plant disease resistance genes. The gene encodes an actin depolymerizing factor that functions in cytoskeleton rearrangement.

  11. Structural basis of protein oxidation resistance: a lysozyme study.

    Science.gov (United States)

    Girod, Marion; Enjalbert, Quentin; Brunet, Claire; Antoine, Rodolphe; Lemoine, Jérôme; Lukac, Iva; Radman, Miroslav; Krisko, Anita; Dugourd, Philippe

    2014-01-01

    Accumulation of oxidative damage in proteins correlates with aging since it can cause irreversible and progressive degeneration of almost all cellular functions. Apparently, native protein structures have evolved intrinsic resistance to oxidation since perfectly folded proteins are, by large most robust. Here we explore the structural basis of protein resistance to radiation-induced oxidation using chicken egg white lysozyme in the native and misfolded form. We study the differential resistance to oxidative damage of six different parts of native and misfolded lysozyme by a targeted tandem/mass spectrometry approach of its tryptic fragments. The decay of the amount of each lysozyme fragment with increasing radiation dose is found to be a two steps process, characterized by a double exponential evolution of their amounts: the first one can be largely attributed to oxidation of specific amino acids, while the second one corresponds to further degradation of the protein. By correlating these results to the structural parameters computed from molecular dynamics (MD) simulations, we find the protein parts with increased root-mean-square deviation (RMSD) to be more susceptible to modifications. In addition, involvement of amino acid side-chains in hydrogen bonds has a protective effect against oxidation Increased exposure to solvent of individual amino acid side chains correlates with high susceptibility to oxidative and other modifications like side chain fragmentation. Generally, while none of the structural parameters alone can account for the fate of peptides during radiation, together they provide an insight into the relationship between protein structure and susceptibility to oxidation.

  12. Structural basis for resistance to diverse classes of NAMPT inhibitors.

    Directory of Open Access Journals (Sweden)

    Weiru Wang

    Full Text Available Inhibiting NAD biosynthesis by blocking the function of nicotinamide phosphoribosyl transferase (NAMPT is an attractive therapeutic strategy for targeting tumor metabolism. However, the development of drug resistance commonly limits the efficacy of cancer therapeutics. This study identifies mutations in NAMPT that confer resistance to a novel NAMPT inhibitor, GNE-618, in cell culture and in vivo, thus demonstrating that the cytotoxicity of GNE-618 is on target. We determine the crystal structures of six NAMPT mutants in the apo form and in complex with various inhibitors and use cellular, biochemical and structural data to elucidate two resistance mechanisms. One is the surprising finding of allosteric modulation by mutation of residue Ser165, resulting in unwinding of an α-helix that binds the NAMPT substrate 5-phosphoribosyl-1-pyrophosphate (PRPP. The other mechanism is orthosteric blocking of inhibitor binding by mutations of Gly217. Furthermore, by evaluating a panel of diverse small molecule inhibitors, we unravel inhibitor structure activity relationships on the mutant enzymes. These results provide valuable insights into the design of next generation NAMPT inhibitors that offer improved therapeutic potential by evading certain mechanisms of resistance.

  13. Determination of structural geometric parameters of industrial ceramic foams by gamma rays transmission and X-rays microtomography

    International Nuclear Information System (INIS)

    Rocha, Wilson Roberto Dejato da

    2005-01-01

    In this work, the gamma rays transmission and X-rays microtomography techniques are used for the evaluation of the porosity and the pore size distribution of SiC ceramic foams. It was also accomplished the three-dimensional images after the determination of samples geometric parameters. The geometric parameters were obtained by two-dimensional images analyses, generated by a Microfocus system, with a CCD camera, an images intensifier, a X-rays tube and an automatic system for rotation of the sample. The spatial resolution of the images was about 32 μm. In the gamma rays transmission methodology, a Nal(Tl) scintillation detector, an 241 Am (59.53 keV, 100 mCi) radioactive source and an automatic X-Z micrometric table was used. The analyzed samples had pores density of 30, 45, 60, 80 and 100 ppi (pores per inch). The gamma rays transmission technique was accurate to supply the porosity of the samples, which ranged about 90% and was in agreement with the values supplied by manufacturer of the foams. The 30 and 45 ppi samples analyzed by X-rays microtomography showed porosity results that agree with the average porosity supplied by the manufacturer. In other hand, the 60, 80 and 100 ppi samples systematically showed average porosity about 4%, lower than the average of the manufacturer. The pore size distributions found through the software IMAGO show the presence of smaller pores than those nominated by the manufacturer. The 30 ppi samples had voids inside the solid material of the ceramic foams structure. Gaussian truncated method, used in the three-dimensional reconstruction, was not able to take into the account the voids inside the solid matrix. (author)

  14. Fe/amorphous ceramics core/shell structured nanoflakes-assembled rod-like architecture for efficient microwave absorber

    Science.gov (United States)

    Li, Xiaolong; Li, Zhenxing; Liu, Xianguo; Zhang, Shihong; Ran, Songlin

    2017-12-01

    A rod-like architecture self-assembled from Fe/amorphous ceramics core/shell structured nanoflakes has been prepared by arc discharging steelmaking slag in an Ar/H2 atmosphere, in which the amorphous ceramic shell is composed of MgO, Al2O3, MgSiO3 and CaSiO3. The electromagnetic absorbing performance of the rod-like architecture is evaluated over the range of 2–18 GHz. Multiple dielectric relaxation of the permittivity is attributed to the size distribution and novel morphology of the rod-like architecture. The experimental permeability is in good agreement with the calculated curves based on the Landau–Lifshitz–Gilbert equation. The magnetic loss ability is superior to the dielectric loss ability, due to the planar anisotropy of flake-shaped particles. At a thickness of 2.4 mm, the minimal reflection loss (RL) can reach  ‑35.04 dB at 10.96 GHz. In particular, the effective bandwidth with RL exceeding  ‑10 dB remains at least 2.56 GHz at a thickness of 1.6–4.1 mm, and exhibits a red shift phenomenon as layer thickness increases. Such efficient EM absorption performances originate from magnetic/dielectric loss ability accompanied by 1/4-wave elimination. The represented work not only provides a good reference for efficient microwave absorption, but also broadens the application of steelmaking slag.

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

    International Nuclear Information System (INIS)

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

    2015-01-01

    In order to increase the solubility of actinides in the glass matrix, the effects of CaO, TiO 2 , and ZrSiO 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 2 , ZrSiO 4 (CTZ) as nucleating agents were added to barium borosilicate glass. • The samples with 45–55 wt% CTZ possess CaZrTi 2 O 7 -2M and CaTiSiO 5 crystalline phases. • CTZ-45 (45wt% CTZ) possesses only CaZrTi 2 O 7 -2M phase after annealing at 680–740 °C. • CTZ-45 possesses CaZrTi 2 O 7 -2M and CaTiSiO 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.

  16. Spectroscopic and calorimetric investigation of short and intermediate-range structures and energetics of amorphous SiCO, SiCN, and SiBCN polymer-derived ceramics

    Science.gov (United States)

    Widgeon, Scarlett J.

    Polymer-derived ceramics (PDCs) are a new class of amorphous ceramics in the Si-B-C-N system that are synthesized by the pyrolysis of silicon-based organic polymers. PDCs are lightweight and are resistant to creep, crystallization, and oxidation at temperatures near 1800 K making them ideal for a variety of high temperature applications. In spite of being X-ray amorphous, these materials display structural heterogeneity at the nanometer length scale. Their structure and resulting properties can be drastically altered by the utilization of preceramic polymers with differing chemistry and architectures. Fundamental understanding of the atomic structure is critical in deciphering the structure-property relationships and ultimately in controlling their properties for specific engineering applications. The short-range atomic structure has been extensively investigated using a variety of techniques, however, the structures at length scales beyond next-nearest neighbors remained highly controversial. Here we report the results of a spectroscopic and calorimetric study of short and intermediate -range structure and energetic of SiOC and SiBCN PDCs derived from a wide variety of precursors. SiOC PDCs with different carbon contents were synthesized from polysiloxane precurors and their structures were studied using high-resolution 13C and 29Si nuclear magnetic resonance (NMR) spectroscopy. The results suggest that these PDCs consists of a continuous mass fractal backbone of corner-shared SiC xO4-x tetrahedral units with "voids" occupied by sp 2-hybridized graphitic carbon. The oxygen-rich SiCxO 4-x units are located at the interior of this backbone with a mass fractal dimension of ~ 2.5, while the carbon-rich units occupy the two-dimensional interface between the backbone and the free carbon nanodomains. Such fractal topology is expected to give rise to unusual mechanical and transport properties characteristic of fractal percolation networks. For example, elastic moduli and

  17. Ceramics research in a high-energy neutron source

    International Nuclear Information System (INIS)

    Clinard, F.W. Jr.

    1989-01-01

    The studies on the irradiation effect to ceramics have added much to the basic understanding of their behavior, for example, the amorphous state of ceramics related to radiation-induced metamictization, the radiation-induced strengthening and toughening due to ultrafine defect aggregates, the in situ degradation of electrical resistivity, the role of radiation-induced defects on thermal conductivity and so on. Most of the irradiation testing on ceramics in the fields of structural and thermal properties have been carried out by using fast fission neutrons of about 1 MeV, but if this energy could be significantly changed, the size and nature of damage cascade and the quantity of transmutation gases produced would change. The significance of neutron source parameters, the special test requirement for ceramics such as the use of miniature specimens, the control of test environment, the transient reduction of electrical resistivity and so on are discussed. A special case of ceramic studies is that on new oxide superconductors. These materials can be made into amorphous state at about 1 dpa using 1 MeV electrons, and are considered to be fairly damage-sensitive. (K.I.)

  18. Repair of pathology of structure with mortar to reject the red ceramics; Reparo de patologia de estrutura com argamassa de rejeito de ceramica vermelha

    Energy Technology Data Exchange (ETDEWEB)

    Santana, Claudeir de Souza; Santos, Juzelia, E-mail: claudeir.santana@gmail.com, E-mail: juzelia@ccivil.cefetmt.br [Instituto Federal de Educacao, Ciencia e Tecnologia de Mato Grosso (IFMT), Cuiaba, MT (Brazil)

    2010-07-01

    The aim of this research is the use of the reject of red ceramic from an industry of bricks and tiles from the region of Cuiaba as mortar for repair of structural pathology, looking for their application to replace the sand and gravel in the process. The mortar produced restores a park bench made of concrete which seat was made of red ceramic and legs of soil-cement bricks. The reject of red ceramic used is from an industry in the region of Cuiaba, discarded at the end of the production process, ground in an appropriate granulometry to simulate a generic type of sand and gravel. Grinding processes were developed and various granulometric curves were drawned. The aggregates produced were characterized from the deposit until the final grinding according to ABNT norms in force, the specific area by BET, was used for microanalysis X-ray diffraction. ABNT standards were used to characterize and compare the results. The mortar produced proved to be adequate for the proposal restoration, it was consistent and cohesive. It was concluded that the mortar produced with recycled aggregate of red ceramic can be used in structural restoration in civil construction to replace the natural aggregate, with cost and environmental benefits. (author)

  19. Natural gas perspectives of diffusion on the brazilian structural ceramics industry; Perspectivas de difusao do gas natural na industria brasileira de ceramica vermelha

    Energy Technology Data Exchange (ETDEWEB)

    Schwob, Marcelo Rousseau Valenca

    2007-03-15

    This study evaluates the perspectives of the natural gas (NG) used by the Brazilian structural ceramics industry (BSCI), according to technological, economic and environmental aspects. It identifies the advantages of using NG, as well as the barriers faced by this energy source. Considering the amount of NG required by the thermal demand of the BSCI processes and the average energy specific use of the furnaces in operation in Brazil, the total consumption of NG will be nearly 12.06 Mm{sup 3/}day. However, the existence of few technical and economical adequate conversion conditions for ceramics furnaces (4% of continuous furnaces) limits the previous potential to only 0.67 Mm{sup 3/}day. In addition, considering the geographic intersection of the ceramics production clusters with the natural gas distribution grid of the Brazilian states, the estimated potential is lowered to 0.28 Mm{sup 3/}day. Yet, the perspective of the NG diffusion in the BSCI in the medium to the long term is more positive, owning to the increasing implementation of large scale production furnaces and cogeneration systems. Also worthwhile to this positive perspective are: the improving demand for certified structural ceramic products, with more quality and value added, and the expanding investment in low income classes dwelling programs. (author)

  20. Structural characterization of an electrically insulating diffusion barrier on a plasma-sprayed ceramic for severe environment applications

    International Nuclear Information System (INIS)

    Joly, Alexandre; Brun, Patrice; Lacombe, Jacques; Tricot, Gregory; Denoirjean, Alain

    2013-01-01

    We investigate in this paper the physical properties and the structure of a protective barrier based on a thermal-sprayed alumina coating. This coating is known to form an electrically insulating barrier that efficiently protects stainless steel structures of melting furnaces subjected to high differences of voltage. Sealing the open and/or interconnected porosity of the alumina coating with aluminum phosphate is also known to improve the protection by mitigating leakage in the ceramic. The sealing procedure has been achieved by (i) impregnating the plasma-sprayed alumina coating with a mono aluminum phosphate (MAlP) solution and (ii) applying a thermal treatment to the system. A waterproof diffusion barrier presenting a good electric insulation is finally obtained and the protective performances were tested on specimens to assess their behavior under aggressive conditions. The formation procedure is characterized by parameters related to the solution and is dependent on the heating rate, the process temperature, and the isothermal duration of the thermal treatment. We show in this paper how these different parameters impact (i) the coating physical properties (thermal and electrical tests) and (ii) the coating structure that has been probed with 31 P solid state nuclear magnetic resonance (NMR). (authors)

  1. Studies on structural, electrical, thermal and magnetic properties of YFeO3 ceramic

    Science.gov (United States)

    Suthar, Lokesh; Jha, V. K.; Bhadala, Falguni; Roy, M.; Sahu, S.; Barbar, S. K.

    2017-10-01

    The polycrystalline ceramic sample of YFeO3 has been synthesized by high-temperature solid-state reaction method using high-purity oxides. The formation of the compound has been confirmed by the room temperature (RT) X-ray diffraction analysis. The refined lattice parameters obtained by Rietveld analysis are: a = 5.5907 Å, b = 7.6082 Å and c = 5.2849 Å with orthorhombic symmetry in space group Pnma. The average grain size obtained from the SEM micrograph is around 2 µm. The three-dimensional surface morphology has been investigated using atomic force microscopy (AFM), and the average roughness measured in the sampling area of 100.07 µm2 is around 142 nm. The frequency- and temperature-dependent dielectric constant has been measured. The material shows high dielectric constant value (750) at RT. The activation energy obtained from dc conductivity using Arrhenius relation σ = σ oexp(-Ea/kT) is 2.12 eV. Thermal analysis shows phase change around 625 K with minimum weight loss (i.e. 1.27% of initial weight) from RT to 1273 K. The magnetization measurement indicates soft magnetic behaviour.

  2. Novel syntactic foams made of ceramic hollow micro-spheres and starch: theory, structure and properties

    Energy Technology Data Exchange (ETDEWEB)

    Islam, M.M.; Kim, H.S. [University of Newcastle, Callaghan, NSW (Australia). Faculty of Engineering & Built Environments

    2007-08-15

    Novel syntactic foams for potential building material applications were developed using starch as binder and ceramic hollow micro-spheres available as waste from coal-fired power stations. Foams of four different micro-sphere size groups were manufactured with either pre- or post-mould gelatinization process. They were of ternary system including voids with a foam density range of approximately 0.33-0.44 g/cc. Compressive failure behaviour and mechanical properties of the manufactured foams were evaluated. Not much difference in failure behaviour or in mechanical properties between the two different processes (pre- and post-mould gels) was found for a given binder content. Compressive failure of all syntactic foams was of shear on plane inclined 45 degrees to compressive loading direction. Failure surfaces of most syntactic foams were characterized by debonded micro-spheres. Compressive strength and modulus of syntactic foams were found to be dependant mainly on binder content but mostly independent of micro-sphere size. Some conditions of relativity arising from properties of constituents leading to the rule of mixtures relationships for compressive strength and to understanding of compressive/transitional failure behaviour were developed. The developed relationships based on the rule of mixtures were partially verified. Some formation of starch webs on failure surfaces was discussed.

  3. Studies on structural, electrical, thermal and magnetic properties of YFeO{sub 3} ceramic

    Energy Technology Data Exchange (ETDEWEB)

    Suthar, Lokesh; Jha, V.K.; Bhadala, Falguni; Roy, M. [M.L. Sukhadia University, Department of Physics, Udaipur, Rajasthan (India); Sahu, S. [B.N. University, Department of Physics, Udaipur, Rajasthan (India); Barbar, S.K. [J.N.V. University, Department of Physics, Jodhpur, Rajasthan (India)

    2017-10-15

    The polycrystalline ceramic sample of YFeO{sub 3} has been synthesized by high-temperature solid-state reaction method using high-purity oxides. The formation of the compound has been confirmed by the room temperature (RT) X-ray diffraction analysis. The refined lattice parameters obtained by Rietveld analysis are: a = 5.5907 Aa, b = 7.6082 Aa and c = 5.2849 Aa with orthorhombic symmetry in space group Pnma. The average grain size obtained from the SEM micrograph is around 2 μm. The three-dimensional surface morphology has been investigated using atomic force microscopy (AFM), and the average roughness measured in the sampling area of 100.07 μm{sup 2} is around 142 nm. The frequency- and temperature-dependent dielectric constant has been measured. The material shows high dielectric constant value (750) at RT. The activation energy obtained from dc conductivity using Arrhenius relation σ = σ {sub o}exp(-Ea/kT) is 2.12 eV. Thermal analysis shows phase change around 625 K with minimum weight loss (i.e. 1.27% of initial weight) from RT to 1273 K. The magnetization measurement indicates soft magnetic behaviour. (orig.)

  4. Structural dynamic and resistance to nuclear air blast

    International Nuclear Information System (INIS)

    Qureshi, S.M.

    2003-01-01

    A need exists to design protective shelters attached to specialized facilities against nuclear airbursts, explosive shocks and impacting projectiles. Designing such structures against nuclear and missile impact is a challenging task that needs to be looked into for design methodology formulation and practicability. Structures can be designed for overpressure pulsed generated by a nuclear explosion as well as the scabbing and perforation/punching of an impacting projectile. This paper discuses and formulates the methods of dynamic analysis and design required to undertake such a task. Structural resistance to peak overpressure pulse for a 20 KT weapons and smaller tactical nuclear weapons of 1 KT (16 psi, overpressure) size as a direct air blast overpressure has been considered in design of walls, beams and slabs of a special structure under review. The design of shear reinforcement as lacing is also carried out. Adopting the philosophy of strengthening and hardening can minimize the effect of air blast overpressure and projectile impact. The objective is to avoid a major structural failure. The structure then needs to be checked against ballistic penetration by a range of weapons or be required to resist explosive penetration from the charge detonated in contact with the structure. There is also a dire need to formulate protective guidelines for all existing and future critical facilities. (author)

  5. A literature review on the new polymer-infiltrated ceramic-network material (PICN).

    Science.gov (United States)

    Facenda, Júlia Cadorim; Borba, Marcia; Corazza, Pedro Henrique

    2018-02-05

    Ceramics and composites are the most used materials for dental application. Recently, the characteristics of both were combined on the called "polymer-infiltrated ceramic-network" (PICN). The aim of this review is to report the behavior of PICN, comparing the findings that may support the correct clinical application. The PICN material is a structure with a sintered ceramic matrix infiltrated with a polymer matrix. Studies evaluated this material microstructure and composition, mechanical properties and adhesive behavior. The most cited mechanical properties are flexural strength, compressive strength, elastic modulus, Weibull modulus, hardness, fracture toughness and fatigue resistance. Most studies compared PICN with feldspathic porcelain, lithium disilicate glass-ceramic, lithium silicate, zirconia-reinforced glass-ceramic, leucite reinforced glass-ceramic, polycrystalline alumina and zirconia. Other studies evaluated a similar material (a nanoceramic resin). The mechanical properties of the PICN are equivalent to the properties of nanoceramic resins, lower to lithium disilicate glass ceramic and superior to feldspathic porcelain. Yet, the findings suggest a highly resistant material to degradation at low loads (close to physiological situation) when cemented on a substrate. © 2018 Wiley Periodicals, Inc.

  6. Transparent ceramic photo-optical semiconductor high power switches

    Science.gov (United States)

    Werne, Roger W.; Sullivan, James S.; Landingham, Richard L.

    2016-01-19

    A photoconductive semiconductor switch according to one embodiment includes a structure of sintered nanoparticles of a high band gap material exhibiting a lower electrical resistance when excited by light relative to an electrical resistance thereof when not exposed to the light. A method according to one embodiment includes creating a mixture comprising particles, at least one dopant, and at least one solvent; adding the mixture to a mold; forming a green structure in the mold; and sintering the green structure to form a transparent ceramic. Additional system, methods and products are also presented.

  7. Potassium Sodium Niobate-Based Lead-Free Piezoelectric Multilayer Ceramics Co-Fired with Nickel Electrodes

    Directory of Open Access Journals (Sweden)

    Shinichiro Kawada

    2015-11-01

    Full Text Available Although lead-free piezoelectric ceramics have been extensively studied, many problems must still be overcome before they are suitable for practical use. One of the main problems is fabricating a multilayer structure, and one solution attracting growing interest is the use of lead-free multilayer piezoelectric ceramics. The paper reviews work that has been done by the authors on lead-free alkali niobate-based multilayer piezoelectric ceramics co-fired with nickel inner electrodes. Nickel inner electrodes have many advantages, such as high electromigration resistance, high interfacial strength with ceramics, and greater cost effectiveness than silver palladium inner electrodes. However, widely used lead zirconate titanate-based ceramics cannot be co-fired with nickel inner electrodes, and silver palladium inner electrodes are usually used for lead zirconate titanate-based piezoelectric ceramics. A possible alternative is lead-free ceramics co-fired with nickel inner electrodes. We have thus been developing lead-free alkali niobate-based multilayer ceramics co-fired with nickel inner electrodes. The normalized electric-field-induced thickness strain (Smax/Emax of a representative alkali niobate-based multilayer ceramic structure with nickel inner electrodes was 360 pm/V, where Smax denotes the maximum strain and Emax denotes the maximum electric field. This value is about half that for the lead zirconate titanate-based ceramics that are widely used. However, a comparable value can be obtained by stacking more ceramic layers with smaller thicknesses. In the paper, the compositional design and process used to co-fire lead-free ceramics with nickel inner electrodes are introduced, and their piezoelectric properties and reliabilities are shown. Recent advances are introduced, and future development is discussed.

  8. Potassium Sodium Niobate-Based Lead-Free Piezoelectric Multilayer Ceramics Co-Fired with Nickel Electrodes

    Science.gov (United States)

    Kawada, Shinichiro; Hayashi, Hiroyuki; Ishii, Hideki; Kimura, Masahiko; Ando, Akira; Omiya, Suetake; Kubodera, Noriyuki

    2015-01-01

    Although lead-free piezoelectric ceramics have been extensively studied, many problems must still be overcome before they are suitable for practical use. One of the main problems is fabricating a multilayer structure, and one solution attracting growing interest is the use of lead-free multilayer piezoelectric ceramics. The paper reviews work that has been done by the authors on lead-free alkali niobate-based multilayer piezoelectric ceramics co-fired with nickel inner electrodes. Nickel inner electrodes have many advantages, such as high electromigration resistance, high interfacial strength with ceramics, and greater cost effectiveness than silver palladium inner electrodes. However, widely used lead zirconate titanate-based ceramics cannot be co-fired with nickel inner electrodes, and silver palladium inner electrodes are usually used for lead zirconate titanate-based piezoelectric ceramics. A possible alternative is lead-free ceramics co-fired with nickel inner electrodes. We have thus been developing lead-free alkali niobate-based multilayer ceramics co-fired with nickel inner electrodes. The normalized electric-field-induced thickness strain (Smax/Emax) of a representative alkali niobate-based multilayer ceramic structure with nickel inner electrodes was 360 pm/V, where Smax denotes the maximum strain and Emax denotes the maximum electric field. This value is about half that for the lead zirconate titanate-based ceramics that are widely used. However, a comparable value can be obtained by stacking more ceramic layers with smaller thicknesses. In the paper, the compositional design and process used to co-fire lead-free ceramics with nickel inner electrodes are introduced, and their piezoelectric properties and reliabilities are shown. Recent advances are introduced, and future development is discussed. PMID:28793646

  9. Preparation, phase structure and microwave dielectric properties of CoLi2/3Ti4/3O4 ceramic

    International Nuclear Information System (INIS)

    Zhou, Huanfu; Liu, Xiaobin; Chen, Xiuli; Fang, Liang

    2012-01-01

    Graphical abstract: For chemical compatibility tests with silver electrode, mixtures of ceramic powders with 20 wt% Ag powders were cofired and analyzed to detect interactions between the low-fired samples and electrodes. XRD patterns and backscattered electron image of CoLi 2/3 Ti 4/3 O 4 ceramics added with 1.5 wt% BCB cofired with Ag at 900 °C for 2 h are presented in . Backscattered electron image analysis reveals no interaction to form new phases after firing. This observation is also confirmed by the evidence of no difference between the XRD patterns before and after firing. It is obvious that the reaction of low-fired CoLi 2/3 Ti 4/3 O 4 ceramics with Ag electrodes did not occur. Highlights: ► A new microwave dielectric ceramic with good properties was reported. ► The addition of BaCu(B 2 O 5 ) can lower the sintering temperature from 1050 °C to 900 °C. ► The addition of BaCu(B 2 O 5 ) does not induce degradation of properties. ► BCB added CoLi 2/3 Ti 4/3 O 4 ceramics can co-fire with Ag electrode. -- Abstract: A new low loss microwave dielectric ceramic with composition of CoLi 2/3 Ti 4/3 O 4 was prepared by a conventional solid-state reaction method. The compound has a cubic spinel structure [Fd-3m (227)] similar to MgFe 2 O 4 with lattice parameters of a = 8.3939 Å, V = 591.42 Å 3 , Z = 8 and ρ = 4.30 g/cm 3 . This ceramic has a low sintering temperature (∼1050 °C) and good microwave dielectric properties with relative permittivity of 21.4, Q × f value of 35,000 GHz and τ f value of −22 ppm/°C. Furthermore, the addition of BaCu(B 2 O 5 ) (BCB) can effectively lower the sintering temperature from 1050 °C to 900 °C and does not induce much degradation of the microwave dielectric properties. Compatibility with Ag electrode indicates that the BCB added CoLi 2/3 Ti 4/3 O 4 ceramics are good candidates for LTCC applications.

  10. [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.

  11. Polymer-Derived Ceramic Fibers

    Science.gov (United States)

    Ichikawa, Hiroshi

    2016-07-01

    SiC-based ceramic fibers are derived from polycarbosilane or polymetallocarbosilane precursors and are classified into three groups according to their chemical composition, oxygen content, and C/Si atomic ratio. The first-generation fibers are Si-C-O (Nicalon) fibers and Si-Ti-C-O (Tyranno Lox M) fibers. Both fibers contain more than 10-wt% oxygen owing to oxidation during curing and lead to degradation in strength at temperatures exceeding 1,300°C. The maximum use temperature is 1,100°C. The second-generation fibers are SiC (Hi-Nicalon) fibers and Si-Zr-C-O (Tyranno ZMI) fibers. The oxygen content of these fibers is reduced to less than 1 wt% by electron beam irradiation curing in He. The thermal stability of these fibers is improved (they are stable up to 1,500°C), but their creep resistance is limited to a maximum of 1,150°C because their C/Si atomic ratio results in excess carbon. The third-generation fibers are stoichiometric SiC fibers, i.e., Hi-Nicalon Type S (hereafter Type S), Tyranno SA, and Sylramic™ fibers. They exhibit improved thermal stability and creep resistance up to 1,400°C. Stoichiometric SiC fibers meet many of the requirements for the use of ceramic matrix composites for high-temperature structural application. SiBN3C fibers derived from polyborosilazane also show promise for structural applications, remain in the amorphous state up to 1,800°C, and have good high-temperature creep resistance.

  12. 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...

  13. 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

  14. Rapid Manufacturing of Durable, Cost-Effective Ceramic Matrix Composites for High Temperature Structures, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Hypersonic vehicles require durable and cost-effective hot structures that do not impose weight penalties such as those associated with the use of non-structural...

  15. Impact Resistance of Structural Ceramics. Part 1. Instrumented Drop- Weight Tests

    Science.gov (United States)

    1976-05-01

    is conventionally obtained for metels using heavy pendulum impact machines in the Charpy or Izod configuration. In the Charpy configuration the... Charpy mode. The tup of the pendulum has a force transducer attached, the output of which is recorded on an oscilloscope. Thus, the load as a function...clear distinction should be made between the energy loss of an impactor in an impact test (the pendulum in a Charpy test or the ball in a DWT) and the

  16. Fracture Resistance, Surface Defects and Structural Strength of Glass

    OpenAIRE

    Rodichev, Y.M.; Veer, F.A.

    2010-01-01

    This paper poses the theory that the fracture resistance of basic float glass is dependent on it physicochemical properties and the surface defects fonned under the float glass production, glass processing and handling at the service conditions compose the aggregate basis for structural glass strength assessment. The effect of loading conditions, constructional and technological factors on the engineering strength of glass can be evaluated in certain cases using fracture mechanics with inform...

  17. Structural, dielectric and magnetic properties of Mn modified xBiFeO{sub 3}-(1−x)BaTiO{sub 3} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Dai, Zhonghua, E-mail: zhdai@mail.xjtu.edu.cn [College of Mechanics and Materials, Hohai University, Nanjing 210098 (China); Ferroic Physics Group, National Institute for Materials Science, Tsukuba 305-0047, Ibaraki (Japan); Liu, Lu; Ying, Guobing; Yuan, Ming [College of Mechanics and Materials, Hohai University, Nanjing 210098 (China); Ren, Xiaobing [Ferroic Physics Group, National Institute for Materials Science, Tsukuba 305-0047, Ibaraki (Japan)

    2017-07-15

    Manganese doped xBiFeO{sub 3}-(1−x)BaTiO{sub 3}(x=0.67–0.82) ceramics were prepared by solid-state method. The structural, dielectric and magnetic properties were investigated after annealing in vacuum at 773 K. X-ray diffraction analysis indicated that all samples crystallized in pure perovskite structure. The ceramics displays a typical ferroelectric loop, with a max remnant polarization P{sub r} of 25.6 µC/cm{sup 2}. The piezoelectric coefficient d{sub 33} of Manganese doped 0.67BiFeO{sub 3}0.33BaTiO{sub 3} is 139 pC/N and its temperature dependence of dielectric constant exhibits a broad anomaly. The Manganese doped 0.75BiFeO{sub 3}0.25BaTiO{sub 3} ceramic shows ferrimagnetism at room temperature, with remnant magnetization M{sub r} of 0.31 emu/g and ferrimagnetic transition temperature T{sub N} of ~420 °C. - Highlights: • In this manuscript, a technique combined Mn doping which is able to fabricate point defects and annealing in vacuum which can stabilize the unstable ion was investigated. We studied the electrical properties of Mn doped BiFeO{sub 3}-BaTiO{sub 3} ceramics after vacuum annealing treatment at appropriate temperature. • Our result is that Mn modification and heat treatment are effective methods to solve the problem of high leakage of BiFeO{sub 3}-BaTiO{sub 3} system ceramic prepared by solid-state method. It exhibited a enhanced field-induced ferromagnetic ordering with promising potential in spintronics and recording media applications.

  18. Structural abnormalities of small resistance arteries in essential hypertension.

    Science.gov (United States)

    Rizzoni, Damiano; Agabiti-Rosei, Enrico

    2012-06-01

    Regardless of the mechanisms that initiate the increase in blood pressure, the development of structural changes in the systemic vasculature is the end result of established hypertension. In essential hypertension, the small arteries smooth muscle cells are restructured around a smaller lumen, and there is no net growth of the vascular wall, while in some secondary forms of hypertension, a hypertrophic remodeling may be detected. Also, in non-insulin-dependent diabetes mellitus, a hypertrophic remodeling of subcutaneous small arteries is present. The results from our own group have suggested that indices of small resistance artery structure, such as the tunica media to internal lumen ratio, may have a strong prognostic significance in hypertensive patients, over and above all other known cardiovascular risk factors. Therefore, the regression of vascular alterations is an appealing goal of antihypertensive treatment. Different antihypertensive drugs seem to have different effect on vascular structure, both in human and in animal models of genetic and experimental hypertension. A complete normalization of small resistance artery structure is demonstrated in hypertensive patients, after long-term and effective therapy with ACE inhibitors, angiotensin II receptor blockers and calcium antagonists. Few data are available in diabetic hypertensive patients; however, blockade of the renin-angiotensin system seems to be effective in this regard. In conclusion, there are several pieces of evidence that suggest that small resistance artery structure may be considered an intermediate endpoint in the evaluation of the effects of antihypertensive therapy; however, there are presently no data available about the prognostic impact of the regression of vascular structural alterations in hypertension and diabetes.

  19. Preparation of Silicon Rubber/2,2'-(3-methyl-4-dihydro-1,3,2-benzoxazinePropane Ablative-resistant Composites and Its Ablative Structure

    Directory of Open Access Journals (Sweden)

    DONG Yimin

    2017-10-01

    Full Text Available Benzoxazine resin is a new generation of anti-ablation resin with high char yield and high-temperature oxidation resistance. Using high temperature vulcanized silicon rubber as ablation resistance matrix and 2,2'-(3-methyl-4-dihydro-1,3,2-benzoxazinepropane as anti-ablation resin, silicon rubber/polybenzoxazine anti-ablation composite was prepared by blending method. The mechanical properties were tested,and the ablation structure and the composition of the composite were investigated by DSC,SEM,FT-IR and Raman.Experimental results show that the polybenzoxazine resin can improve the ablation resistance property of silicone rubber composite. The composite has good ablation resistance and mechanical property when the addition of polybenzoxazine resin reaches 20 phr. After ablated by oxygen acetylene flame,the ablation layer is divided into three obvious layers as surface ceramic layer,pyrolysis carbonization layer and base layer. The surface ceramic layer formed in the progress of ablation plays a positive role in the ablation property of the composite material.

  20. Structure, morphology and optical-luminescence investigations of spinel ZnGa2O4 ceramics co-doped with Mn2+ and Eu3+ ions

    Science.gov (United States)

    Kravets, O.; Zaremba, O.; Shpotyuk, Ya.; Luchechko, A.; Szmuc, K.; Cebulski, J.; Ingram, A.; Shpotyuk, O.

    2018-02-01

    The polycrystalline zinc gallate ZnGa2O4: Mn2+ and ZnGa2O4: Mn2+, Eu3+ samples have been synthesized via high-temperature solid-state reaction ceramic technique. The obtained ceramics have been characterized employing the methods of X-ray diffraction analysis, transmission electron microscopy, energy-dispersive X-ray spectroscopy, positron annihilation lifetime spectroscopy and optical-luminescent spectroscopy. The XRD analysis testified in favor of successful formation of spinel structure in the prepared samples with small amount of additional phase observed in the ZnGa2O4: Mn2+, Eu3+ ceramics. The grains of irregular shape with a homogeneous distribution of Eu3+ ions in a volume were identified with TEM technique. The band gap of ZnGa2O4: Mn2+ spinel was estimated from optical absorption spectra in UV-Vis range. The characteristic bands related to electronic transitions of Mn2+ and Eu3+ ions were found in optical absorption and excitation spectra. The photoluminescence emission spectra exhibited matrix luminescence along with emission band of Mn2+ ions and narrow lines of Eu3+ ions in blue, green and red spectral region, respectively. The intensity ratio of Eu3+ emission lines confirms the high asymmetry around Eu3+ ions. These findings correlate well with results of positron annihilation lifetime spectroscopy showing intense reduction of positron trapping rate deeply in ceramics grains due to Eu3+ ions penetration.

  1. Crystal structural evolution and hybrid improper ferroelectricity in Ruddlesden-Popper Ca3-xSrxTi2O7 ceramics

    Science.gov (United States)

    Li, G. J.; Liu, X. Q.; Lu, J. J.; Zhu, H. Y.; Chen, X. M.

    2018-01-01

    Hybrid improper ferroelectricity (HIF) has been proposed as a candidate approach to create room-temperature multiferroic materials with an intrinsic electric-field controlled magnetism effect, and HIFs in bi-layered Ruddlesden-Popper Ca3-xSrxTi2O7 ceramics have been confirmed in the present work. The ferroelectric hysteresis loops are observed in these ceramics at room temperature, and the polar orthorhombic structures with oxygen octahedral rotation and tilt modes have been confirmed by room-temperature X-ray powder diffraction. The amplitudes of oxygen octahedral rotation and tilt modes decrease with the increasing x value, which in turn leads to the decrease of remnant polarization in these ceramics. A first-order phase transition has been evidenced by the differential scanning calorimetry measurement, and the temperature of phase transition decreases linearly with the increasing content of strontium cations. It is found that the amplitude of oxygen octahedral distortion is the dominating factor that affects ferroelectric polarization in partial-ordered bi-layered Ca3Ti2O7-based ceramics.

  2. Resistance to antibiotics: limit theorems for a stochastic SIS model structured by level of resistance.

    Science.gov (United States)

    Boëlle, Pierre-Yves; Thomas, Guy

    2016-12-01

    The rise of bacterial resistance to antibiotics is a major Public Health concern. It is the result of two interacting processes: the selection of resistant bacterial strains under exposure to antibiotics and the dissemination of bacterial strains throughout the population by contact between colonized and uncolonized individuals. To investigate the resulting time evolution of bacterial resistance, Temime et al. (Emerg Infect Dis 9:411-417, 2003) developed a stochastic SIS model, which was structured by the level of resistance of bacterial strains. Here we study the asymptotic properties of this model when the population size is large. To this end, we cast the model within the framework of measure valued processes, using point measures to represent the pattern of bacterial resistance in the compartments of colonized individuals. We first show that the suitably normalized model tends in probability to the solution of a deterministic differential system. Then we prove that the process of fluctuations around this limit tends in law to a Gaussian process in a space of distributions. These results, which generalize those of Kurtz (CBMS-NSF regional conference series in applied mathematics, vol 36. Society for Industrial and Applied Mathematics (SIAM), Philadelphia, 1981, chap. 8) on SIR models, support the validity of the deterministic approximation and quantify the rate of convergence.

  3. High Temperature Advanced Structural Composites. Volume 2. Ceramic Matrix Composites, Fiber Processing and Properties, and Interfaces

    Science.gov (United States)

    1993-04-02

    crystal i sapphire). alumina is prized as a gemstone (sapphire or ruby. depending upon the impurities present) and for special applications such as...resistance heating technique, strains are estimated from displacement measurements using LVOTS, while temperature is measured using a two- colour ...Mechanical design ture is read using a two- colour pyrometer with a4-20mA linear output (Mikronx 7778 series) and a 2.1.1. Mounting frame. The apparatus

  4. Influence of mechanical activation on elelctrical properties of cordierite ceramics

    Directory of Open Access Journals (Sweden)

    Đorđević N.G.

    2008-01-01

    Full Text Available The goal of the presented research was to find a possible correlation of the process parameters and functional properties of cordierite based ceramic materials. A three component oxide mixture was prepared containing MgO+Al2O3+SiO2 in the 2:2:5 ratio with the addition of 10% Bi2O3. Mixtures were mechanochemically activated 5 and 240 minutes in a mill with ceramic balls, and sintered at temperatures from 1173-1573K. Structural transformations were determined by the XRD method. Quantitative measures of the functional sample properties, capacity Cc and electrical resistance Rρ as well as tangens of dielectric loss angle tg α were used. The results obtained proved that there is a correlation between mechanochemical activation and properties of cordierite ceramics.

  5. A comparison of corrosion resistance of cobalt-chromium-molybdenum metal ceramic alloy fabricated with selective laser melting and traditional processing.

    Science.gov (United States)

    Zeng, Li; Xiang, Nan; Wei, Bin

    2014-11-01

    A cobalt-chromium-molybdenum alloy fabricated by selective laser melting is a promising material; however, there are concerns about the change in its corrosion behavior. The purpose of this study was to evaluate the changes in corrosion behavior of a cobalt-chromium-molybdenum alloy fabricated by the selective laser melting technique before and after ceramic firing, with traditional processing of cobalt-chromium-molybdenum alloy serving as a control. Two groups of specimens were designated as group selective laser melting and group traditional. For each group, 20 specimens with a cylindrical shape were prepared and divided into 4 cells: selective laser melting as-cast, selective laser melting fired in pH 5.0 and 2.5, traditional as-cast, and traditional fired in pH 5.0 and 2.5. Specimens were prepared with a selective laser melting system for a selective laser melting alloy and the conventional lost wax technique for traditional cast alloy. After all specimen surfaces had been wet ground with silicon carbide paper (1200 grit), each group of 10 specimens was put through a series of ceramic firing cycles. Microstructure, Vickers microhardness, surface composition, oxide film thickness, and corrosion behavior were examined for specimens before and after ceramic firing. Three-way ANOVA was used to evaluate the effect of porcelain firing and pH values on the corrosion behavior of the 2 alloys (α=.05). Student t tests were used to compare the Vickers hardness. Although porcelain firing changed the microstructure, microhardness, and x-ray photoelectron spectroscopy results, it showed no significant influence on the corrosion behavior of the selective laser melting alloy and traditional cast alloy (P>.05). No statistically significant influence was found on the corrosion behavior of the 2 alloys in different pH value solutions (P>.05). The porcelain firing process had no significant influence on the corrosion resistance results of the 2 alloys. Compared with traditional

  6. Microstructure, hardness, corrosion resistance and porcelain shear bond strength comparison between cast and hot pressed CoCrMo alloy for metal-ceramic dental restorations.

    Science.gov (United States)

    Henriques, B; Soares, D; Silva, F S

    2012-08-01

    The purpose of this study was to compare the microstructure, hardness, corrosion resistance and metal-porcelain bond strength of a CoCrMo dental alloy obtained by two routes, cast and hot pressing. CoCrMo alloy substrates were obtained by casting and hot pressing. Substrates' microstructure was examined by the means of Optical Microscopy (OM) and by Scanning Electron Microscope (SEM) and Energy Dispersive X-ray Spectroscopy (EDS). Hardness tests were performed in a microhardness indenter. The electrochemical behavior of substrates was investigated through potentiodynamic tests in a saline solution (8g NaCl/L). Substrates were bonded to dental porcelain and metal-porcelain bond strength was assessed by the means of a shear test performed in a universal test machine (crosshead speed: 0.5 mm/min) until fracture. Fractured surfaces as well as undestroyed interface specimens were examined with Stereomicroscopy and SEM-EDS. Data was analyzed with Shapiro-Wilk test to test the assumption of normality. The t-test (pmicrostructures whereas hot pressed specimens exhibited a typical globular microstructure with a second phase spread through the matrix. The hardness registered for hot pressed substrates was greater than that of cast specimens, 438±24HV/1 and 324±8HV/1, respectively. Hot pressed substrates showed better corrosion properties than cast ones, i.e. higher OCP; higher corrosion potential (E(corr)) and lower current densities (i(corr)). No significant difference was found (p<0.05) in metal-ceramic bond strength between cast (116.5±6.9 MPa) and hot pressed (114.2±11.9 MPa) substrates. The failure type analysis revealed an adhesive failure for all specimens. Hot pressed products arise as an alternative to cast products in dental prosthetics, as they impart enhanced mechanical and electrochemical properties to prostheses without compromising the metal-ceramic bond strength. Copyright © 2012 Elsevier Ltd. All rights reserved.

  7. [Ceramic brackets].

    Science.gov (United States)

    Mølsted, K

    1992-01-01

    Because of the many drawbacks of the hard and brittle material, ceramic brackets should not be used uncritically for orthodontic treatments. If ceramic brackets are used, the following guidelines should be observed: 1. If large and complicated tooth movements are involved, conventional bracket systems should be considered. 2. Occlusion on ceramic brackets is to be avoided. 3. Sharp instruments should be used with extreme care to avoid scratching the ceramic surface. Metal ligatures must not be used. 4. The length of the treatment is extended, probably because of the increased friction. 5. The problems connected with removing the brackets have not yet been solved. Be particularly careful of weakened teeth. 6. Esthetically, ceramic brackets function satisfactorily, but transparent elastic ligatures do not. They rapidly become discoloured and need frequent replacement. Nor are there as yet any "invisible arch wires", apart from some few, extremely flexible "white" arch wires. The ceramic bracket has no doubt come to stay, but there have been many difficulties in the "running-in" period, and the problems are far from solved yet. New ceramic brackets are coming onto the market all the time, and only future clinical studies can show whether they will become a genuine alternative to the conventional bracket.

  8. Structural basis of protein oxidation resistance: a lysozyme study.

    Directory of Open Access Journals (Sweden)

    Marion Girod

    Full Text Available Accumulation of oxidative damage in proteins correlates with aging since it can cause irreversible and progressive degeneration of almost all cellular functions. Apparently, native protein structures have evolved intrinsic resistance to oxidation since perfectly folded proteins are, by large most robust. Here we explore the structural basis of protein resistance to radiation-induced oxidation using chicken egg white lysozyme in the native and misfolded form. We study the differential resistance to oxidative damage of six different parts of native and misfolded lysozyme by a targeted tandem/mass spectrometry approach of its tryptic fragments. The decay of the amount of each lysozyme fragment with increasing radiation dose is found to be a two steps process, characterized by a double exponential evolution of their amounts: the first one can be largely attributed to oxidation of specific amino acids, while the second one corresponds to further degradation of the protein. By correlating these results to the structural parameters computed from molecular dynamics (MD simulations, we find the protein parts with increased root-mean-square deviation (RMSD to be more susceptible to modifications. In addition, involvement of amino acid side-chains in hydrogen bonds has a protective effect against oxidation Increased exposure to solvent of individual amino acid side chains correlates with high susceptibility to oxidative and other modifications like side chain fragmentation. Generally, while none of the structural parameters alone can account for the fate of peptides during radiation, together they provide an insight into the relationship between protein structure and susceptibility to oxidation.

  9. Effect of Ba addition on the structural, dielectric and ferroelectric properties of Na0.5Bi0.5TiO3 ceramics

    Directory of Open Access Journals (Sweden)

    Suchanicz J.

    2015-06-01

    Full Text Available Lead-free (Na0.5Bi0.51-xBaxTiO3 (x = 0, 0.04 and 0.06 ceramics were fabricated by conventional solid phase sintering process. X-ray diffraction analysis shows that obtained specimens possess the perovskite structure. The microstructure study shows a dense structure, in good agreement with the relative density determined by the Archimedes method (above 95 %. Electric permittivity anomaly is shifted to low temperature after Ba doping of NBT. The pyroelectric and hysteresis loops measurements show that polarization and coercive field increases and decreases, respectively, after Ba doping of NBT. The obtained results are discussed in terms of ions/lattice imperfections, which create local electromechanical fields. The investigated ceramics are considered to be promising candidates for lead-free electronic materials.

  10. Mechanical energy dissipation in natural ceramic composites.

    Science.gov (United States)

    Mayer, George

    2017-12-01

    Ceramics and glasses, in their monolithic forms, typically exhibit low fracture toughness values, but rigid natural marine ceramic and glass composites have shown remarkable resistance to mechanical failure. This has been observed in load-extension behavior by recognizing that the total area under the curve, notably the part beyond the yield point, often conveys substantial capacity to carry mechanical load. The mechanisms underlying the latter observations are proposed as defining factors for toughness that provide resistance to failure, or capability to dissipate energy, rather than fracture toughness. Such behavior is exhibited in the spicules of glass sponges and in mollusk shells. There are a number of similarities in the manner in which energy dissipation takes place in both sponges and mollusks. It was observed that crack diversion, a new form of crack bridging, creation of new surface area, and other important energy-dissipating mechanisms occur and aid in "toughening". Crack tolerance, key to energy dissipation in these natural composite materials, is assisted by promoting energy distribution over large volumes of loaded specimens by minor components of organic constituents that also serve important roles as adhesives. Viscoelastic deformation was a notable characteristic of the organic component. Some of these energy-dissipating modes and characteristics were found to be quite different from the toughening mechanisms that are utilized for more conventional structural composites. Complementary to those mechanisms found in rigid natural ceramic/organic composites, layered architectures and very thin organic layers played major roles in energy dissipation in these structures. It has been demonstrated in rigid natural marine composites that not only architecture, but also the mechanical behavior of the individual constituents, the nature of the interfaces, and interfacial bonding play important roles in energy dissipation. Additionally, the controlling

  11. 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.

  12. Oxide ceramics

    International Nuclear Information System (INIS)

    Ryshkewitch, E.; Richerson, D.W.

    1985-01-01

    The book explores single-phase ceramic oxide systems from the standpoint of physical chemistry and technology. This second edition also focuses on advances in technology since publication of the original edition. These include improvements in raw materials and forming and sintering techniques, and the major role that oxide ceramics have had in development of advanced products and processes. The text is divided into five major sections: general fundamentals of oxide ceramics, advances in aluminum oxide technology, advances in zirconia technology, and advances in beryllium oxide technology

  13. Improvement of microstructure and mechanical properties of high dense SiC ceramics manufactured by high-speed hot pressing

    International Nuclear Information System (INIS)

    Voyevodin, V.; Sayenko, S.; Lobach, K.; Tarasov, R.; Zykova, A.; Svitlychnyi, Ye.; Surkov, A.; Abelentsev, V.; Ghaemi, H.; Szkodo, M.; Gajowiec, G.; Kmiec, M.; Antoszkiewicz, M.

    2017-01-01

    Non-oxide ceramics possess high physical-mechanical properties, corrosion and radiation resistance, which can be used as a protective materials for radioactive wastes disposal. The aim of the present study was the manufacturing of high density SiC ceramics with advanced physical and mechanical parameters. The high performance on the properties of produced ceramics was determined by the dense and monolithic structure. The densified silicon carbide samples possessed good mechanical strength, with a high Vickers micro hardness up to 28.5 GPa.

  14. Photovoltage versus microprobe sheet resistance measurements on ultrashallow structures

    DEFF Research Database (Denmark)

    Clarysse, T.; Moussa, A.; Parmentier, B.

    2010-01-01

    recently been observed between junction photovoltage (JPV) based tools and a micrometer-resolution four-point probe (M4PP) tool on a variety of difficult, state-of-the-art sub-32-nm complementary metal-oxide semiconductor structures (low energy and cluster implants, with/without halo, flash- and laser......-based millisecond anneal). Conventional four-point probe tools fail on almost all of these samples due to excessive probe penetration, whereas in several cases variable probe spacing (using a conventional spreading resistance probe tool) [T. Clarysse , Mater. Sci. Eng. R. 47, 123 (2004)] still gives useful values...... to within about 20%-35% due to its limited probe penetration (5-10 nm at 5 g load). M4PP measurements give systematically a sensible and reproducible result. This is also the case for JPV-based sheet resistance measurements, although these appear to be prone to correct calibration procedures...

  15. Tensile Properties of Open Cell Ceramic Foams

    Czech Academy of Sciences Publication Activity Database

    Dlouhý, Ivo; Řehořek, Lukáš; Chlup, Zdeněk

    2009-01-01

    Roč. 409, - (2009), s. 168-175 ISSN 1013-9826. [Fractography of Advanced Ceramics /3./. Stará Lesná, 07.09.2008-10.09.2008] R&D Projects: GA ČR(CZ) GA106/06/0724; GA ČR GD106/05/H008 Institutional research plan: CEZ:AV0Z20410507 Keywords : tensile test * ceramics foam * open porosity * tensile strength Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass

  16. Estimation of local mechanical properties of highly porous ceramic materials

    Czech Academy of Sciences Publication Activity Database

    Marcián, P.; Majer, Z.; Dlouhý, Ivo; Florian, Z.

    2012-01-01

    Roč. 106, č. 3 (2012), S476-S477 ISSN 0009-2770 R&D Projects: GA ČR(CZ) GA101/09/1821 Institutional support: RVO:68081723 Keywords : cellular structures * tensile test * microCT * image processing * FEM Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass Impact factor: 0.453, year: 2012 http://chemicke-listy.cz/docs/full/2012_s3_s405-s441.pdf

  17. Hydrothermal degradation of tetragonal ZrO2 ceramic components used in dental applications

    International Nuclear Information System (INIS)

    Mukaeda, L.E.; Robin, A.; Taguchi, S.P.

    2009-01-01

    With the evolution of the dental restoration techniques, a considerable growth in the demand of ceramic products occurred. These materials present good strength associated to reliability. In this work, micrometric and nanometric scale tetragonal ZrO 2 blocks were sintered at 1500 deg C-2h and 1350 deg C-2h, respectively, ground and polished. Ceramics with relative density higher than 98% were obtained. The specimens were immersed in hot water (150 deg C), for times ranging from 10h to 30h. The mass variation of the samples was measured and the crystalline phases present before and after the degradation tests were identified by X-ray diffractometry, in order to evaluate the capacity of these ceramics in resisting to aqueous medium exposure. Materials with nanometric structure present higher resistance to degradation than those with micrometric scale, and this interferes in structural stability after the test, and reduces the martensitic transformation. (author)

  18. Tailored ceramics

    International Nuclear Information System (INIS)

    Harker, A.B.

    1988-01-01

    In polyphase tailored ceramic forms two distinct modes of radionuclide immobilization occur. At high waste loadings the radionuclides are distributed through most of the ceramic phases in dilute solid solution, as indicated schematically in this paper. However, in the case of low waste loadings, or a high loading of a waste with low radionuclide content, the ceramic can be designed with only selected phases containing the radionuclides. The remaining material forms nonradioactive phases which provide a degree of physical microstructural isolation. The research and development work with polyphase ceramic nuclear waste forms over the past ten years is discussed. It has demonstrated the critical attributes which suggest them as a waste form for future HLW disposal. From a safety standpoint, the crystalline phases in the ceramic waste forms offer the potential for demonstrable chemical durability in immobilizing the long-lived radionuclides in a geologic environment. With continued experimental research on pure phases, analysis of mineral analogue behavior in geochemical environments, and the study of radiation effects, realistic predictive models for waste form behavior over geologic time scales are feasible. The ceramic forms extend the degree of freedom for the economic optimization of the waste disposal system

  19. Durability and CMAS Resistance of Advanced Environmental Barrier Coatings Systems for SiC/SiC Ceramic Matrix Composites

    Science.gov (United States)

    Zhu, Dongming

    2015-01-01

    Environmental barrier coatings (EBCs) and SiCSiC ceramic matrix composites (CMCs) systems will play a crucial role in next generation turbine engines for hot-section component applications because of their ability to significantly increase engine operating temperatures with improved efficiency, reduce engine weight and cooling requirements. This paper will emphasize advanced environmental barrier coating developments for SiCSiC turbine airfoil components, by using advanced coating compositions and processing, in conjunction with mechanical and environment testing and durability validations. The coating-CMC degradations and durability in the laboratory simulated engine fatigue-creep and complex operating environments are being addressed. The effects of Calcium-Magnesium-Alumino-Silicate (CMAS) from road sand or volcano-ash deposits on the degradation mechanisms of the environmental barrier coating systems will be discussed. The results help understand the advanced EBC-CMC system performance, aiming at the durability improvements of more robust, prime-reliant environmental barrier coatings for successful applications of the component technologies and lifing methodologies.

  20. Structural perfection and residual electric resistance of tungsten single crystals

    International Nuclear Information System (INIS)

    Tagirova, D.M.; Dyakina, V.P.; Startsev, V.E.; Esin, V.O.

    1997-01-01

    A study was made into residual relative resistance (RRR) and structural perfection (SP) of tungsten single crystals, grown by electron beam zone melting using seeding crystals of several orientations, namely, , , , . The single crystals were of 99.98 and 99.9995 wt.% purity. The RRR value is found to depend on crystallographic orientation of an axis of crystal growth and to correlate with SP. Single crystals of different purity are differ in the nature of orientational dependences. It is shown that the correlation between RRR and SP of crystals is mainly due to conduction electron scattering by subgrain boundaries (internal size effect)

  1. Mechanical Property Analysis on Sandwich Structured Hybrid Composite Made from Natural Fibre, Glass Fibre and Ceramic Fibre Wool Reinforced with Epoxy Resin

    Science.gov (United States)

    Bharat, K. R.; Abhishek, S.; Palanikumar, K.

    2017-06-01

    Natural fibre composites find wide range of applications and usage in the automobile and manufacturing industries. They find lack in desired properties, which are required for present applications. In current scenario, many developments in composite materials involve the synthesis of Hybrid composite materials to overcome some of the lacking properties. In this present investigation, two sandwich structured hybrid composite materials have been made by reinforcing Aloe Vera-Ceramic Fibre Wool-Glass fibre with Epoxy resin matrix and Sisal fibre-Ceramic Fibre Wool-Glass fibre with Epoxy resin matrix and its mechanical properties such as Tensile, Flexural and Impact are tested and analyzed. The test results from the two samples are compared and the results show that sisal fibre reinforced hybrid composite has better mechanical properties than aloe vera reinforced hybrid composite.

  2. Global Current Circuit Structure in a Resistive Pulsar Magnetosphere Model

    Science.gov (United States)

    Kato, Yugo. E.

    2017-12-01

    Pulsar magnetospheres have strong magnetic fields and large amounts of plasma. The structures of these magnetospheres are studied using force-free electrodynamics. To understand pulsar magnetospheres, discussions must include their outer region. However, force-free electrodynamics is limited in it does not handle dissipation. Therefore, a resistive pulsar magnetic field model is needed. To break the ideal magnetohydrodynamic (MHD) condition E\\cdot B=0, Ohm’s law is used. This work introduces resistivity depending upon the distance from the star and obtain a self-consistent steady state by time integration. Poloidal current circuits form in the magnetosphere while the toroidal magnetic field region expands beyond the light cylinder and the Poynting flux radiation appears. High electric resistivity causes a large space scale poloidal current circuit and the magnetosphere radiates a larger Poynting flux than the linear increase outside of the light cylinder radius. The formed poloidal-current circuit has width, which grows with the electric conductivity. This result contributes to a more concrete dissipative pulsar magnetosphere model.

  3. Phase structure, dielectric, and piezoelectric properties of (K0.94-xNaxLi0.06)(Nb0.94Sb0.06)O3 lead-free ceramics

    International Nuclear Information System (INIS)

    Fu, Lingling; Lin, Dunmin; Zheng, Qiaoji; Wu, Xiaochun; Xu, Chenggang

    2012-01-01

    Lead-free piezoelectric ceramics (K 0.94-x Na x Li 0.06 )(Nb 0.94 Sb 0.06 )O 3 have been fabricated by a conventional ceramic technique and the effects of K + /Na + ratio on the structure and piezoelectric properties of the ceramics have been studied. All the ceramics possess a pure perovskite structure. The coexistence of tetragonal and orthorhombic phases is formed at room temperature in the ceramics with 0.45 ≤ x ≤ 0.55. The tetragonal-orthorhombic phase-transition temperature T O-T decreases from 110 to 54 C with x increasing from 0.35 to 0.55 and then increases from 84 to 144 C with x further increasing from 0.6 to 0.7, while the Curie temperature T C deceases from 388 to 348 C with x increasing from 0.35 to 0.70. Because of the coexistence of the two phases near room temperature, the ceramics with x = 0.50 exhibit the optimum piezoelectric properties: d 33 = 230 pC/N and k p = 49%. The ceramics possess good time stability of piezoelectric properties. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  4. 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...

  5. Indentation Damage in Ceramics.

    Science.gov (United States)

    1987-05-30

    resistance have finer grain sizes (cf. A999 and Vistal ). Most interesting, however, is the quantitative correlation between grinding resistance and...a 0.1 3 4.3 2.2 Vistal I a 0.1 20 4.1 1.7 Vistal 1, a 0.1 40 4.6 1.5 Glass-ceramic Pyroceram c - 1.5 2.3 2.0 Macor C _ 13 2.3 1.0 a. Coors Porcelain

  6. Structural and ferroelectrical properties of bismuth titanate ceramic powders prepared by mechanically assisted synthesis

    Directory of Open Access Journals (Sweden)

    Lazarević Z.Ž.

    2007-01-01

    Full Text Available Nanosized bismuth titanate, Bi4Ti3O12, was prepared via a high-energy ball milling process through mechanically assisted synthesis directly from the oxide mixture of Bi2O3 and TiO2. The Bi4Ti3O12 phase started to form after 1 h of milling. With increasing the milling time from 3 to 12 h, the particle size of formed Bi4Ti3O12 did not reduce significantly. The grain size was less than 16 nm and showed a strong tendency to agglomeration. The nucleation and phase formation of Bi4Ti3O12, crystal structure, microstructure, powder grain size and specific surface area were followed by XRD, Rietveld refinement analysis, SEM and the BET specific surface area measurements. Raman spectroscopy was used to explain the structural properties of Bi4Ti3O12 powder, prepared by mechanically assisted synthesis. Reduction in grain size with the increase of milling time was also noted (change in the position and relative intensity, which indicated changes in the structure, caused by nanodimension grains. The sample milled for 12 h and subsequently sintered at 1000°C for 24 h exhibited a hysteresis loop, confirming that the synthesized material possesses ferroelectric properties. .

  7. Microstructure and fracture analysis of fully ceramic microencapsulated fuel

    International Nuclear Information System (INIS)

    Lee, H. G.; Kim, D. J.; Park, J. Y.; Kim, W. J.; Lee, S. J.

    2015-01-01

    Nuclear fuel enhancing the accident tolerance is satisfied two parts. First, the performance has to be retained compared to the existing UO 2 nuclear fuel and zircaloy cladding system under the normal operation condition. Second, under the severe accident condition, the high temperature structural integrity has to be kept and the generation rate of hydrogen has to be reduced largely. FCM nuclear fuel is composed of tristructural isotropic(TRISO) fuel particle and SiC ceramic matrix. SiC ceramic matrix play an essential part in protecting fission product. In the FCM fuel concept, fission product is doubly protected by TRISO coating layer and SiC ceramic matrix compared to the current commercial UO 2 fuel system. SiC ceramic has excellent properties for fuel application. SiC ceramic has low neutron absorption cross-section, excellent irradiation resistivity and high thermal conductivity. Additionally, the relative thermal conductivity of the SiC ceramic as compared to UO 2 is quite good, reducing operational release of fission products form the fuel. TRISO coating layer which is deposited on UO 2 kernel is consists of PyC/SiC/PyC trialyer and buffer PyC layer. SiC matrix composite with TRISO particle was fabricated by hot pressing. 3 to 20 wt.% of sintering additives were added to investigate reaction between sintering additives and outer PyC layer of TRISO coating layer. The relative densities of all specimens show above 92%. The reaction between sintering additives and PyC is observed in most TRISO particles, the thickness of reactants shows about ten micrometers. The thermal shock resistance of SiC matrix composite was investigated

  8. Ceramic process and plant design for high-level nuclear waste immobilization

    International Nuclear Information System (INIS)

    Grantham, L.F.; McKisson, R.L.; De Wames, R.E.; Guon, J.; Flintoff, J.F.; McKenzie, D.E.

    1983-01-01

    In the last 3 years, significant advances in ceramic technology for high-level nuclear waste solidification have been made. Product quality in terms of leach-resistance, compositional uniformity, structural integrity, and thermal stability promises to be superior to borosilicate glass. This paper addresses the process effectiveness and preliminary designs for glass and ceramic immobilization plants. The reference two-step ceramic process utilizes fluid-bed calcination (FBC) and hot isostatic press (HIP) consolidation. Full-scale demonstration of these well-developed processing steps has been established at DOE and/or commercial facilities for processing radioactive materials. Based on Savannah River-type waste, our model predicts that the capital and operating cost for the solidification of high-level nuclear waste is about the same for the ceramic and glass options. However, when repository costs are included, the ceramic option potentially offers significantly better economics due to its high waste loading and volume reduction. Volume reduction impacts several figures of merit in addition to cost such as system logistics, storage, transportation, and risk. The study concludes that the ceramic product/process has many potential advantages, and rapid deployment of the technology could be realized due to full-scale demonstrations of FBC and HIP technology in radioactive environments. Based on our finding and those of others, the ceramic innovation not only offers a viable backup to the glass reference process but promises to be a viable future option for new high-level nuclear waste management opportunities

  9. New approach to the elucidation of corrosion mechanism of ceramics by the ion implantation

    International Nuclear Information System (INIS)

    Saito, J.; Hayashi, K.; Tachi, Y.; Kano, S.

    1998-08-01

    Ceramics possessing high temperature strength are promising materials for the structural application in severe environment. The development of ceramics has been carried out in order to use them in FBR environment such as liquid sodium. In particular, corrosion behavior of ceramics has been investigated to improve the corrosion resistance in liquid sodium. However, the corrosion mechanism of ceramics was not comprehended in detail even now. Because corrosion products which were deposited on the surface of test pieces during corrosion test and played an important role in corrosion behavior, were not detected distinctly after thr corrosion test. In this study, an ion implantation technique was applied to understand the corrosion mechanism of ceramics in stead of the conventional corrosion test. Sodium ions were implanted in ceramics (100 keV, 1.9 x 10 17 ions/cm 2 ) and then heat treatment was performed at either 923 K or 823 K for 36 ks in argon atmosphere. After that, products on the surface were analyzed using SEM and TEM observation and X-ray diffraction. Consequently, the corrosion products were not identified exactly, but their presence was confirmed on the surface. It was caused by the minute amount of corrosion products. In future, it is necessary to carry systematically out the implantation and heat treatment under various conditions. Therefore, it seems that the beneficial information will be obtained to understand the corrosion mechanism of ceramics. (author)

  10. Antimicrobial ceramics. Kokinsei ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Yoshinari, T.; Uchida, M. (Shinagawa Fuel Co. Ltd., Nagoya (Japan))

    1993-07-01

    In recent years, the occurrence of infection by methicillin resistant staphylococcus aureus (MRSA), for which almost all antibiotics do not affect, in facilities such as hospitals is causing trouble. The antimicrobial property of silver has been known empirically since the ancient times. However, since 1985, so called silver zeolite in which zeolite carries silver ions has become utilized as an inorganic antimicrobial agent with silver as its constituent. In this article, the effect of inhibiting MRSA propagation of antimicrobial fibers containing silver zeolite is explained centering around the physical properties of silver zeolite. MRSA has resistance against antibiotics, methicillin which is mainly used at present. When the antimicrobial power of silver zeolite is compared with those of copper zeolite and zinc zeolite, the antimicrobial power of silver zeolite is the strongest and further increases as the silver ion concentration in the zeolite increases. Silver zeolite is safe to use and used for tools and clothes to be used in the fields of food and medical care. 12 refs., 3 figs., 8 tabs.

  11. Structural Characterization of Highly Corrosion-resistant Steel

    Directory of Open Access Journals (Sweden)

    Adriana Lančok

    2015-12-01

    Full Text Available Structural features of novel corrosion-resistant LC 200N steel were investigated. Mössbauer spectrometry was chosen as a principal method of investigation. Surface as well as bulk properties were studied using Conversion Electron Mössbauer Spectrometry and transmission technique, respectively. Complex behaviour of magnetic and non-magnetic phases was identified in the samples by these two techniques. Chemical composition was checked by neutron activation analysis and X-ray fluorescence technique. Structural arrangement was studied by scanning electron microscopy with energy dispersive spectrometry and transmission electron microscopy. They unveiled regions with fairly varied Cr concentrations. Basing on a simple model of two different Cr concentrations, the relative areas of the Mössbauer sextets were modelled by a linear combination of two binomial distributions.

  12. Stability analysis of multipoint tool equipped with metal cutting ceramics

    Science.gov (United States)

    Maksarov, V. V.; Khalimonenko, A. D.; Matrenichev, K. G.

    2017-10-01

    The article highlights the issues of determining the stability of the cutting process by a multipoint cutting tool equipped with cutting ceramics. There were some recommendations offered on the choice of parameters of replaceable cutting ceramic plates for milling based of the conducted researches. Ceramic plates for milling are proposed to be selected on the basis of value of their electrical volume resistivity.

  13. Characterization of the interaction between glazes and ceramic bodies

    Czech Academy of Sciences Publication Activity Database

    Kavanová, M.; Kloužková, A.; Kloužek, Jaroslav

    2017-01-01

    Roč. 61, č. 3 (2017), s. 267-275 ISSN 0862-5468 Institutional support: RVO:67985891 Keywords : glazes * ceramics * thermal analysis * coefficients of the thermal expansion * dilatometry Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass OBOR OECD: Ceramics Impact factor: 0.439, year: 2016

  14. Survival of Dicor glass-ceramic dental restorations over 16 years. Part III: effect of luting agent and tooth or tooth-substitute core structure.

    Science.gov (United States)

    Malament, K A; Socransky, S S

    2001-11-01

    The influence of different types of restorative design features on the long-term survival of Dicor glass-ceramic restorations is only partially understood. This study examined the effect of different types of luting agents and preparation core structures on the survival of Dicor glass-ceramic restorations functioning in vivo. A total of 1444 Dicor glass-ceramic restorations were placed on the teeth of 417 adults. Failure was defined as a restoration that required remake because of material fracture. The survival of restorations of different types, with different luting agents and preparation core structures, was described with Kaplan-Meier survival functions. The significance of differences in survival between different tooth or tooth-substitute preparation core structures and different luting agents was determined with the log-rank test. The probability of survival of a typical acid-etched Dicor restoration luted to gold preparation core structures was 91% at 16 years compared with 75% for dentin preparation core structures (P<.01). The survival of acid-etched Dicor restorations luted to dentin preparations was significantly better than nonacid-etched restorations luted to dentin. Acid-etched Dicor restorations luted with resin composite exhibited a more favorable survival function than those luted with glass ionomer (P<.01) and zinc phosphate (P<.05). Differences between restorations luted with glass ionomer or zinc phosphate agents were not significant. Acid-etched Dicor restorations luted to gold preparation core structures exhibited significantly better intraoral survival than restorations luted to dentin. Acid-etched Dicor restorations survived better than nonacid-etched restorations when luted to dentin preparations. Acid-etched Dicor restorations luted with resin composite exhibited more favorable survivor functions than restorations luted with glass ionomer or zinc phosphate agents.

  15. Evaluation of fracture resistance of endodontically treated maxillary premolars, restored with ceromer or heat-pressed ceramic inlays and fixed with dual-resin cements.

    Science.gov (United States)

    Ortega, V L; Pegoraro, L F; Conti, P C R; do Valle, A L; Bonfante, G

    2004-04-01

    The aim of this study was to evaluate the fracture resistance of endodontically maxillary premolars restored with mesio-occlusal-distal (MOD) inlays made with ceramic (IPS-Empress 2) and ceromer (Targis) and luted with three different dual-cured resin cements (Enforce, Variolink II, Panavia F). Sixty maxillary premolars were randomly distributed into six groups, according to their mesio-distal and facio-lingual dimensions. The teeth were endodontically treated and MOD cavities prepared. After the restorations were cemented, the samples were thermocycled and submitted to an axial compressive load by the action of a rounded end steel cylinder contacting the incline planes of occlusal surfaces of the teeth. The mode of fracture was analysed with a microscope. The best results were found with the combinations (cement/restorative material) Enforce/Targis (107.57 kgf) and Enforce/Empress (90.21 kgf) followed by Variolink II/Targis (86.44 kgf)-Variolink II/Empress (84.07 kgf) and Panavia F/Targis (82.43 kgf)-Panavia F/Empress (76.73 kgf). Analysis of variance (P < 0.05) showed a significant difference between Enforce and Panavia cements regardless of the restorative material. Considering the same luting agent there was no statistically significant difference between the restorative materials. Fracture of lingual cusps occurred in 55 of the 60 teeth and most of them were of the cohesive type.

  16. Fetal Sheep Mesenteric Resistance Arteries: Functional and Structural Maturation.

    Science.gov (United States)

    Müller, Julia J; Schwab, Matthias; Rosenfeld, Charles R; Antonow-Schlorke, Iwa; Nathanielsz, Peter W; Rakers, Florian; Schubert, Harald; Witte, Otto W; Rupprecht, Sven

    2017-01-01

    Fetal blood pressure increases during late gestation; however, the underlying vascular mechanisms are unclear. Knowledge of the maturation of resistance arteries is important to identify the mechanisms and vulnerable periods for the development of vascular dysfunction in adulthood. We determined the functional and structural development of fetal sheep mesenteric resistance arteries using wire myography and immunohistochemistry. Media mass and distribution of myosin heavy-chain isoforms showed no changes between 0.7 (100 ± 3 days) and 0.9 (130 ± 3 days) gestation. However, from 0.7 to 0.9 gestation, the resting wall tension increased accompanied by non-receptor-dependent (potassium) and receptor-dependent (noradrenaline; endothelin-1) increases in vasocontraction. Angiotensin II had no contractile effect at both ages. Endothelium-dependent relaxation to acetylcholine and prostaglandin E2 was absent at 0.7 but present at 0.9 gestation. Augmented vascular responsiveness was paralleled by the maturation of sympathetic and sensory vascular innervation. Non-endothelium-dependent relaxation to nitric oxide showed no maturational changes. The expression of vasoregulator receptors/enzymes did not increase between 0.7 and 0.9 gestation. Vascular maturation during late ovine gestation involves an increase in resting wall tension and the vasoconstrictor and vasodilator capacity of the mesenteric resistance arteries. Absence of structural changes in the tunica media and the lack of an increase in vasoregulator receptor/enzyme expression suggest that vasoactive responses are due to the maturation of intracellular pathways at this gestational age. © 2017 S. Karger AG, Basel.

  17. Electronic structure of the Y Ba2 Cu3 O7-x high temperature superconductor ceramic

    International Nuclear Information System (INIS)

    Lima, G.A.R.

    1990-01-01

    We investigate the electronic structure of superconductor Y Ba 2 Cu 3 O 7-x through a molecular cluster approach. The calculations are performed self consistently through a semi empirical L.C.A.O. technique, where different charge states are considered. The correlation effects are taken into account by configuration interaction procedure (INDO/CI). The results for the larger cluster yield a density of states showing a strong p-d covalency resulting in a width of around 8,0 eV for the valence band. The optical excitations is analyzed in detail and compared with the experimental data. (author)

  18. Determination of superlattice effect on metal–ceramic nano-structures

    Directory of Open Access Journals (Sweden)

    J.C. Caicedo

    2015-01-01

    Full Text Available Binary nitrides multilayer systems were grown on silicon (100 substrates with the aim to study the coherent assembly in HfN/VN material. Multilayers films were grown via reactive r.f. magnetron sputtering technique by systematically varying the bilayer period (Λ and the bilayer number (n while maintaining constant the total coating thickness (∼2.4 μm. The layers were characterized by high angle X-ray diffraction (HA-XRD, low angle X-ray diffraction (LA-XRD. HfN and VN layers were analyzed by X-ray photoelectron spectroscopy (XPS and electron and transmission microscopy (TEM. HA-XRD results showed preferential growth in the face-centered cubic (111 crystal structure for HfN/VN multilayer systems with the epitaxial relation (111 [100]HfN//(200 [100]VN. The maximum coherent assembly was observed with presence of satellite peaks. With this idea, ternary and binary nitrides films have been designed and deposited on Si (100 substrates with bilayer periods (Λ in a broad range, from nanometers to micrometers. The films were fabricated to study the structural evolution, coherent assembly progress and optical properties such as the critical angle, dispersion coefficient, index of refraction for HfN/VN multilayers with decreasing bilayer thickness.

  19. Development of New Type Seawater Resistant Steel and the Research of Its Structure and Corrosion Resistance

    Science.gov (United States)

    Yin, Baoliang; Yin, Shaojiang; Liu, Zhiyong; Wang, Yunge; Yu, Hao; Li, Haixu; Zhou, Tao

    This paper investigated two kinds of corrosion resistant low alloy steels depending on the environment of the North China see (Steel S) and South China sea (Steel N), respectively. The mechanical and corrosion properties of the two steels were analyzed in this paper. Tin was added into both steels to improve the corrosion resistance. Structure and mechanical properties of the two steels were detected, and the results revealed that the microstructures of both steels were ferrite and little divorced pearlite. The yield strength and impact toughness at -40°C of the steel S are 423MPa and 98 J, respectively. The yield strength and impact toughness at -40°C of the steel N are 437 MPa and 70 J, respectively. The properties mentioned above met or even exceeded the requirement (yield strength 355 MPa, toughness 34 J) in these areas. The corrosion resistant properties of the two steels were also investigated via the means of immersion test and electrochemical experiment. The immersion test indicated that the corrosion rate of steel S and steel N was 0.00938 mg/h·cm2 and 0.00838 mg/h·cm2, respectively, when completely immersed for 168 hours, and the corrosion rate was much lower than that of E36. The Electrochemical experiments showed that the corrosion potential (Ecorr) of both steels was higher in contrast to E36, which indicated a lower corrosion trend.

  20. Interfacial microstructure and shear strength of reactive air brazed oxygen transport membrane ceramic-metal alloy joints

    Science.gov (United States)

    FR, Wahid Muhamad; Yoon, Dang-Hyok; Raju, Kati; Kim, Seyoung; Song, Kwang-sup; Yu, Ji Haeng

    2018-01-01

    To fabricate a multi-layered structure for maximizing oxygen production, oxygen transport membrane (OTM) ceramics need to be joined or sealed hermetically metal supports for interfacing with the peripheral components of the system. Therefore, in this study, Ag-10 wt% CuO was evaluated as an effective filler material for the reactive air brazing of dense Ce0.9Gd0.1O2-δ-La0.7Sr0.3MnO3±δ (GDC-LSM) OTM ceramics. Thermal decomposition in air and wetting behavior of the braze filler was performed. Reactive air brazing was performed at 1050 °C for 30 min in air to join GDC-LSM with four different commercially available high temperature-resistant metal alloys, such as Crofer 22 APU, Inconel 600, Fecralloy, and AISI 310S. The microstructure and elemental distribution of the ceramic-ceramic and ceramic-metal interfaces were examined from polished cross-sections. The mechanical shear strength at room temperature for the as-brazed and isothermally aged (800 °C for 24 h) joints of all the samples was compared. The results showed that the strength of the ceramic-ceramic joints was decreased marginally by aging; however, in the case of metal-ceramic joints, different decreases in strengths were observed according to the metal alloy used, which was explained based on the formation of different oxide layers at the interfaces.