Sample records for yttrium-containing advanced ceramics

  1. Process for making a titanium diboride-chromium diboride-yttrium titanium oxide ceramic composition

    DOEpatents

    Holcombe, Cressie E.; Dykes, Norman L.

    1992-01-01

    A ceramic composition composition is described. The ceramic composition consists essentially of from about 84 to 96 w/o titanium diboride, from about 1 to 9 w/o chromium diboride, and from about 3 to aobut 15 w/o yttrium-titanium-oxide. A method of making the ceramic composition is also described. The method of making the ceramic composition comprises the following steps: Step 1--A consolidated body containing stoichiometric quantities of titanium diboride and chromium diboride is provided. Step 2--The consolidated body is enclosed in and in contact with a thermally insulated package of yttria granules having a thickness of at least 0.5 inches. Step 3--The consolidated body enclosed in the thermally insulated package of yttria granules is heated in a microwave oven with microwave energy to a temperature equal to or greater than 1,900 degrees centigrade to sinter and uniformly disperse yttria particles having a size range from about 1 to about 12 microns throughout the consolidated body forming a densified body consisting essentially of titanium diboride, chromium diboride, and yttrium-titanium-oxide. The resulting densified body has enhanced fracture toughness and hardness.

  2. Process for making a titanium diboride-chromium diboride-yttrium titanium oxide ceramic composition

    DOEpatents

    Holcombe, C.E.; Dykes, N.L.

    1992-04-28

    A ceramic composition is described. The ceramic composition consists essentially of from about 84 to 96 w/o titanium diboride, from about 1 to 9 w/o chromium diboride, and from about 3 to about 15 w/o yttrium-titanium-oxide. A method of making the ceramic composition is also described. The method of making the ceramic composition comprises the following steps: Step 1--A consolidated body containing stoichiometric quantities of titanium diboride and chromium diboride is provided. Step 2--The consolidated body is enclosed in and in contact with a thermally insulated package of yttria granules having a thickness of at least 0.5 inches. Step 3--The consolidated body enclosed in the thermally insulated package of yttria granules is heated in a microwave oven with microwave energy to a temperature equal to or greater than 1,900 degrees centigrade to sinter and uniformly disperse yttria particles having a size range from about 1 to about 12 microns throughout the consolidated body forming a densified body consisting essentially of titanium diboride, chromium diboride, and yttrium-titanium-oxide. The resulting densified body has enhanced fracture toughness and hardness. No Drawings

  3. Quantitative description of yttrium aluminate ceramic composition by means of Er+3 microluminescence spectrum

    NASA Astrophysics Data System (ADS)

    Videla, F. A.; Tejerina, M. R.; Moreira-Osorio, L.; Conconi, M. S.; Orzi, D. J. O.; Flores, T.; Ponce, L. V.; Bilmes, G. M.; Torchia, G. A.

    2018-05-01

    The composition of erbium-doped yttrium aluminate ceramics was analyzed by means of confocal luminescence spectroscopy, EDX, and X-ray diffraction. A well-defined linear correlation was found between a proposed estimator computed from the luminescence spectrum and the proportion of ceramic phases coexisting in different samples. This result shows the feasibility of using erbium luminescence spectroscopy to perform a quantitative determination of different phases of yttrium aluminates within a micrometric region in nanograined ceramics.

  4. Titanium diboride-chromium diboride-yttrium titanium oxide ceramic composition and a process for making the same

    DOEpatents

    Holcombe, Cressie E.; Dykes, Norman L.

    1991-01-01

    A ceramic composition is described. The ceramic composition consists essentially of from about 84 to 96 w/o titanium diboride, from about 1 to 9 w/o chromium diboride, and from about 3 to about 15 w/o yttrium-titanium-oxide. A method of making the ceramic composition is also described. The method of making the ceramic composition comprises the following steps: Step 1--A consolidated body containing stoichiometric quantities of titanium diboride and chromium diboride is provided. Step 2--The consolidated body is enclosed in and in contact with a thermally insulated package of yttria granules having a thickness of at least 0.5 inches. Step 3--The consolidated body enclosed in the thermally insulated package of yttria granules is heated in a microwave oven with microwave energy to a temperature equal to or greater than 1,900 degrees centigrade to sinter and uniformly disperse yttria particles having a size range from about 1 to about 12 microns throughout the consolidated body forming a densified body consisting essentially of titanium diboride, chromium diboride, and yttrium-titanium-oxide. The resulting densified body has enhanced fracture toughness and hardness.

  5. Fabrication of dense yttrium oxyfluoride ceramics by hot pressing and their mechanical, thermal, and electrical properties

    NASA Astrophysics Data System (ADS)

    Tahara, Ryuki; Tsunoura, Toru; Yoshida, Katsumi; Yano, Toyohiko; Kishi, Yukio

    2018-06-01

    Excellent corrosion-resistant materials have been strongly required to reduce particle contamination during the plasma process in semiconductor production. Yttrium oxyfluoride can be a candidate as highly corrosion-resistant material. In this study, three types of dense yttrium oxyfluoride ceramics with different oxygen contents, namely, YOF, Y5O4F7 and Y5O4F7 + YF3, were fabricated by hot pressing, and their mechanical, thermal, and electrical properties were evaluated. Y5O4F7 ceramics showed an excellent thermal stability up to 800 °C, a low loss factor, and volume resistivity comparable to conventional plasma-resistant oxides, such as Y2O3. From these results, yttrium oxyfluoride ceramics are strongly suggested to be used as electrostatic chucks in semiconductor production.

  6. Thermoelectric properties of the yttrium-doped ceramic oxide SrTiO3

    NASA Astrophysics Data System (ADS)

    Khan, Tamal Tahsin; Ur, Soon-Chul

    2017-01-01

    The doping dependence of the thermoelectric figure of merit, ZT, of the ceramic oxide SrTiO3 at high temperature has been studied. In this study, yttrium was used as the doping element. A conventional solid-state reaction method was used for the preparation of Y-doped SrTiO3. The doping level in SrTiO3 was controlled to be in the doping range of 2 - 10 mole%. Almost all the yttrium atoms incorporated into the SrTiO3 provided charge carriers, as was observed by using X-ray diffraction pattern. The relative densities of all the samples varied from 98.53% to 99.45%. The thermoelectric properties, including the electrical conductivity σ, Seebeck coefficient S, thermal conductivity k, and the figure of merit, ZT, were investigated at medium temperatures. The ZT value showed an obvious doping level dependence, in which a value as high as 0.18 is realized at 773 K for a doping of 8 mole%.

  7. Positron annihilation in transparent ceramics

    NASA Astrophysics Data System (ADS)

    Husband, P.; Bartošová, I.; Slugeň, V.; Selim, F. A.

    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.

  8. [Structure and properties of colored dental tetragonal zirconia stabilized by yttrium ceramics].

    PubMed

    Yi, Yuan-fu; Wang, Chen; Wen, Ning; Lin, Yong-zhao; Tian, Jie-mo

    2009-10-01

    To investigate the structure, mechanical and low temperature aging properties of colored dental zirconia ceramics. 5 graded colored dental zirconia ceramics were made by adding colorants and their combinations into a 3Y-TZP (tetragonal zirconia stabilized by 3mol% yttrium) powder, the green body were compacted at 200 MPa, pre-sinter at 1,050 degrees C and maintained for 2 h, then densely sintered at 1,500 degrees C for 2 h. Specimens were cut from each of the 5 graded colored blocks. Physical, mechanical properties as well as chemical stability were tested, microstructure were observed, crystalline phase were identified by X-ray diffraction (XRD), aging properties were assessed by measurement of the relative content of monoclinic phase and bending strength testing. The overall density of colored zirconia ceramics was over 99.7%, linear shrinkage was about 20%, while thermal expansion coefficient was about 11 x 10(-6) x degrees C(-1), the crystalline phase was tetragonal, bending strength was over 900 MPa which was slightly lowered than that of the uncolored zirconia, fracture toughness was slightly higher. Good chemical stability in acetic acid was observed. After aging treatment, tetragonal-to-monoclinic phase transformation was detected up to 40%, while bending strength was not significantly degraded. The results showed that colored 3Y-TZP ceramics presented good mechanical properties even after aging treatments, and was suitable for dental clinical use.

  9. Raman and Infrared Spectroscopy of Yttrium Aluminum Borate Glasses and Glass-ceramics

    NASA Technical Reports Server (NTRS)

    Bradley, J.; Brooks, M.; Crenshaw, T.; Morris, A.; Chattopadhyay, K.; Morgan, S.

    1998-01-01

    Raman spectra of glasses and glass-ceramics in the Y2O3-Al2O3-B2O3 system are reported. Glasses with B2O3 contents ranging from 40 to 60 mole percent were prepared by melting 20 g of the appropriate oxide or carbonate powders in alumina crucibles at 1400 C for 45 minutes. Subsequent heat treatments of the glasses at temperatures ranging from 600 to 800 C were performed in order to induce nucleation and crystallization. It was found that Na2CO3 added to the melt served as a nucleating agent and resulted in uniform bulk crystallization. The Raman spectra of the glasses are interpreted primarily in terms of vibrations of boron - oxygen structural groups. Comparison of the Raman spectra of the glass-ceramic samples with spectra of aluminate and borate crystalline materials reveal that these glasses crystallize primarily as yttrium aluminum borate, YAl3(BO3)4.

  10. Advanced Ceramic Armor Materials

    DTIC Science & Technology

    1990-05-11

    materials, toughened alumina, fiber -reinforced glass matrix composites, and multilayer-gradient materials for ballistic testing. Fabrication and...material systems: Multilayer advanced armor materials consisting of a hard ceramic faceplate bonded to a graphite fiber -reinforced glass matrix...toughened alumina, and fiber - applied studies of advanced reinforced ceramic matrix glass and glass -ceramic composites for ballistic testing. technologies

  11. FOREWORD: Focus on Advanced Ceramics Focus on Advanced Ceramics

    NASA Astrophysics Data System (ADS)

    Ohashi, Naoki

    2011-06-01

    Much research has been devoted recently to developing technologies for renewable energy and improving the efficiency of the processes and devices used in industry and everyday life. Efficient solutions have been found using novel materials such as platinum and palladium-based catalysts for car exhaust systems, samarium-cobalt and neodymium-iron-boron permanent magnets for electrical motors, and so on. However, their realization has resulted in an increasing demand for rare elements and in their deficit, the development of new materials based on more abundant elements and new functionalities of traditional materials. Moreover, increasing environmental and health concerns demand substitution of toxic or hazardous substances with nature-friendly alternatives. In this context, this focus issue on advanced ceramics aims to review current trends in ceramics science and technology. It is related to the International Conference on Science and Technology of Advanced Ceramics (STAC) held annually to discuss the emerging issues in the field of ceramics. An important direction of ceramic science is the collaboration between experimental and theoretical sciences. Recent developments in density functional theory and computer technology have enabled the prediction of physical and chemical properties of ceramics, thereby assisting the design of new materials. Therefore, this focus issue includes articles devoted to theory and advanced characterization techniques. As mentioned above, the potential shortage of rare elements is becoming critical to the industry and has resulted in a Japanese government initiative called the 'Ubiquitous Element Strategy'. This focus issue also includes articles related to this strategy and to the associated topics of energy conversion, such as phosphors for high-efficiency lighting and photocatalysts for solar-energy harvesting. We hope that this focus issue will provide a timely overview of current trends and problems in ceramics science and

  12. Method of forming a relatively stable slip of silicon metal particles and yttrium containing particles

    DOEpatents

    Dickie, Ray A.; Mangels, John A.

    1984-01-01

    The method concerns forming a relatively stable slip of silicon metal particles and yttrium containing particles. In one embodiment, a casting slip of silicon metal particles is formed in water. Particles of a yttrium containing sintering aid are added to the casting slip. The yttrium containing sintering aid is a compound which has at least some solubility in water to form Y.sup.+3 ions which have a high potential for totally flocculating the silicon metal particles into a semiporous solid. A small amount of a fluoride salt is added to the casting slip which contains the yttrium containing sintering aid. The fluoride salt is one which will produce fluoride anions when dissolved in water. The small amount of the fluoride anions produced are effective to suppress the flocculation of the silicon metal particles by the Y.sup.+3 ions so that all particles remain in suspension in the casting slip and the casting slip has both an increased shelf life and can be used to cast articles having a relatively thick cross-section. The pH of the casting slip is maintained in a range from 7.5 to 9. Preferably, the fluoride salt used is one which is based on a monovalent cation such as sodium or ammonia. The steps of adding the yttrium containing sintering aid and the fluoride salt may be interchanged if desired, and the salt may be added to a solution containing the sintering aid prior to addition of the silicon metal particles.

  13. The behaviour of selected yttrium containing bioactive glass microspheres in simulated body environments.

    PubMed

    Cacaina, D; Ylänen, H; Simon, S; Hupa, M

    2008-03-01

    The study aims at the manufacture and investigation of biodegradable glass microspheres incorporated with yttrium potentially useful for radionuclide therapy of cancer. The glass microspheres in the SiO2-Na2O-P2O5-CaO-K2O-MgO system containing yttrium were prepared by conventional melting and flame spheroidization. The behaviour of the yttrium silicate glass microspheres was investigated under in vitro conditions using simulated body fluid (SBF) and Tris buffer solution (TBS), for different periods of time, according to half-life time of the Y-90. The local structure of the glasses and the effect of yttrium on the biodegradability process were evaluated by Fourier Transform Infrared (FT-IR) spectroscopy and Back Scattered Electron Imaging of Scanning Electron Microscopy (BEI-SEM) equipped with Energy Dispersive X-ray (EDX) analysis. UV-VIS spectrometry and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) was used for analyzing the release behaviour of silica and yttrium in the two used solutions. The results indicate that the addition of yttrium to a bioactive glass increases its structural stability which therefore, induced a different behaviour of the glasses in simulated body environments.

  14. Process for producing advanced ceramics

    DOEpatents

    Kwong, Kyei-Sing

    1996-01-01

    A process for the synthesis of homogeneous advanced ceramics such as SiC+AlN, SiAlON, SiC+Al.sub.2 O.sub.3, and Si.sub.3 N.sub.4 +AlN from natural clays such as kaolin, halloysite and montmorillonite by an intercalation and heat treatment method. Included are the steps of refining clays, intercalating organic compounds into the layered structure of clays, drying the intercalated mixture, firing the treated atmospheres and grinding the loosely agglomerated structure. Advanced ceramics produced by this procedure have the advantages of homogeneity, cost effectiveness, simplicity of manufacture, ease of grind and a short process time. Advanced ceramics produced by this process can be used for refractory, wear part and structure ceramics.

  15. Advanced Ceramics for Use as Fuel Element Materials in Nuclear Thermal Propulsion Systems

    NASA Technical Reports Server (NTRS)

    Valentine, Peter G.; Allen, Lee R.; Shapiro, Alan P.

    2012-01-01

    With the recent start (October 2011) of the joint National Aeronautics and Space Administration (NASA) and Department of Energy (DOE) Advanced Exploration Systems (AES) Nuclear Cryogenic Propulsion Stage (NCPS) Program, there is renewed interest in developing advanced ceramics for use as fuel element materials in nuclear thermal propulsion (NTP) systems. Three classes of fuel element materials are being considered under the NCPS Program: (a) graphite composites - consisting of coated graphite elements containing uranium carbide (or mixed carbide), (b) cermets (ceramic/metallic composites) - consisting of refractory metal elements containing uranium oxide, and (c) advanced carbides consisting of ceramic elements fabricated from uranium carbide and one or more refractory metal carbides [1]. The current development effort aims to advance the technology originally developed and demonstrated under Project Rover (1955-1973) for the NERVA (Nuclear Engine for Rocket Vehicle Application) [2].

  16. Advanced ceramic materials for next-generation nuclear applications

    NASA Astrophysics Data System (ADS)

    Marra, John

    2011-10-01

    The nuclear industry is at the eye of a 'perfect storm' with fuel oil and natural gas prices near record highs, worldwide energy demands increasing at an alarming rate, and increased concerns about greenhouse gas (GHG) emissions that have caused many to look negatively at long-term use of fossil fuels. This convergence of factors has led to a growing interest in revitalization of the nuclear power industry within the United States and across the globe. Many are surprised to learn that nuclear power provides approximately 20% of the electrical power in the US and approximately 16% of the world-wide electric power. With the above factors in mind, world-wide over 130 new reactor projects are being considered with approximately 25 new permit applications in the US. Materials have long played a very important role in the nuclear industry with applications throughout the entire fuel cycle; from fuel fabrication to waste stabilization. As the international community begins to look at advanced reactor systems and fuel cycles that minimize waste and increase proliferation resistance, materials will play an even larger role. Many of the advanced reactor concepts being evaluated operate at high-temperature requiring the use of durable, heat-resistant materials. Advanced metallic and ceramic fuels are being investigated for a variety of Generation IV reactor concepts. These include the traditional TRISO-coated particles, advanced alloy fuels for 'deep-burn' applications, as well as advanced inert-matrix fuels. In order to minimize wastes and legacy materials, a number of fuel reprocessing operations are being investigated. Advanced materials continue to provide a vital contribution in 'closing the fuel cycle' by stabilization of associated low-level and high-level wastes in highly durable cements, ceramics, and glasses. Beyond this fission energy application, fusion energy will demand advanced materials capable of withstanding the extreme environments of high

  17. Demonstrating the potential of yttrium-doped barium zirconate electrolyte for high-performance fuel cells.

    PubMed

    Bae, Kiho; Jang, Dong Young; Choi, Hyung Jong; Kim, Donghwan; Hong, Jongsup; Kim, Byung-Kook; Lee, Jong-Ho; Son, Ji-Won; Shim, Joon Hyung

    2017-02-23

    In reducing the high operating temperatures (≥800 °C) of solid-oxide fuel cells, use of protonic ceramics as an alternative electrolyte material is attractive due to their high conductivity and low activation energy in a low-temperature regime (≤600 °C). Among many protonic ceramics, yttrium-doped barium zirconate has attracted attention due to its excellent chemical stability, which is the main issue in protonic-ceramic fuel cells. However, poor sinterability of yttrium-doped barium zirconate discourages its fabrication as a thin-film electrolyte and integration on porous anode supports, both of which are essential to achieve high performance. Here we fabricate a protonic-ceramic fuel cell using a thin-film-deposited yttrium-doped barium zirconate electrolyte with no impeding grain boundaries owing to the columnar structure tightly integrated with nanogranular cathode and nanoporous anode supports, which to the best of our knowledge exhibits a record high-power output of up to an order of magnitude higher than those of other reported barium zirconate-based fuel cells.

  18. Biochemical investigation of yttrium(III) complex containing 1,10-phenanthroline: DNA binding and antibacterial activity.

    PubMed

    Khorasani-Motlagh, Mozhgan; Noroozifar, Meissam; Moodi, Asieh; Niroomand, Sona

    2013-03-05

    Characterization of the interaction between yttrium(III) complex containing 1,10-phenanthroline as ligand, [Y(phen)2Cl(OH2)3]Cl2⋅H2O, and DNA has been carried out by UV absorption, fluorescence spectra and viscosity measurements in order to investigate binding mode. The experimental results indicate that the yttrium(III) complex binds to DNA and absorption is decreasing in charge transfer band with the increase in amount of DNA. The binding constant (Kb) at different temperatures as well as thermodynamic parameters, enthalpy change (ΔH°) and entropy change (ΔS°), were calculated according to relevant fluorescent data and Vant' Hoff equation. The results of interaction mechanism studies, suggested that groove binding plays a major role in the binding of the complex and DNA. The activity of yttrium(III) complex against some bacteria was tested and antimicrobial screening tests shown growth inhibitory activity in the presence of yttrium(III) complex. Copyright © 2013 Elsevier B.V. All rights reserved.

  19. Ceramic Technology for Advanced Heat Engines Project

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

    Not Available

    1989-08-01

    The Ceramic Technology for Advanced Heat Engines Project was developed by the Department of Energy's Office of Transportation Systems (OTS) in Conservation and Renewable Energy. This project, part of the OTS's Advanced 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 Department of Energy (DOE), National Aeronautics and Space Administration (NASA), and Department of Defense (DoD) advanced heat engine programs have provided evidence that the operation of ceramic parts in high-temperature engine environments is feasible. However, these programs have also demonstrated that additional researchmore » 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.« less

  20. Ceramic electrolyte coating methods

    DOEpatents

    Seabaugh, Matthew M.; Swartz, Scott L.; Dawson, William J.; McCormick, Buddy E.

    2004-10-12

    Processes for preparing aqueous suspensions of a nanoscale ceramic electrolyte material such as yttrium-stabilized zirconia. The invention also includes a process for preparing an aqueous coating slurry of a nanoscale ceramic electrolyte material. The invention further includes a process for depositing an aqueous spray coating slurry including a ceramic electrolyte material on pre-sintered, partially sintered, and unsintered ceramic substrates and products made by this process.

  1. Ceramic Technology For Advanced Heat Engines Project

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

    Not Available

    1990-12-01

    Significant accomplishments in fabricating ceramic components for the Department of Energy (DOE), National Aeronautics and Space Administration (NASA), and Department of Defense (DoD) advanced heat engine programs have provided evidence that the operation of ceramic parts in high-temperature engine environments is feasible. However, these programs have also demonstrated that additional research is needed in materials and processing development, design methodology, and data base and life prediction before industry will have a sufficient technology base from which to produce reliable cost-effective ceramic engine components commercially. The objective of the project is to develop the industrial technology base required for reliable ceramicsmore » for application in advanced automotive heat engines. The project approach includes determining the mechanisms controlling reliability, improving processes for fabricating existing ceramics, developing new materials with increased reliability, and testing these materials in simulated engine environments to confirm reliability. Although this is a generic materials project, the focus is on the structural ceramics for advanced gas turbine and diesel engines, ceramic bearings and attachments, and ceramic coatings for thermal barrier and wear applications in these engines. This advanced materials technology is being developed in parallel and close coordination with the ongoing DOE and industry proof of concept engine development programs. To facilitate the rapid transfer of this technology to U.S. industry, the major portion of the work is being done in the ceramic industry, with technological support from government laboratories, other industrial laboratories, and universities. Abstracts prepared for appropriate papers.« less

  2. Advanced ceramic matrix composites for TPS

    NASA Technical Reports Server (NTRS)

    Rasky, Daniel J.

    1992-01-01

    Recent advances in ceramic matrix composite (CMC) technology provide considerable opportunity for application to future aircraft thermal protection system (TPS), providing materials with higher temperature capability, lower weight, and higher strength and stiffness than traditional materials. The Thermal Protection Material Branch at NASA Ames Research Center has been making significant progress in the development, characterization, and entry simulation (arc-jet) testing of new CMC's. This protection gives a general overview of the Ames Thermal Protection Materials Branch research activities, followed by more detailed descriptions of recent advances in very-high temperature Zr and Hf based ceramics, high temperature, high strength SiC matrix composites, and some activities in polymer precursors and ceramic coating processing. The presentation closes with a brief comparison of maximum heat flux capabilities of advanced TPS materials.

  3. Parametric Weight Comparison of Advanced Metallic, Ceramic Tile, and Ceramic Blanket Thermal Protection Systems

    NASA Technical Reports Server (NTRS)

    Myers, David E.; Martin, Carl J.; Blosser, Max L.

    2000-01-01

    A parametric weight assessment of advanced metallic panel, ceramic blanket, and ceramic tile thermal protection systems (TPS) was conducted using an implicit, one-dimensional (I-D) finite element sizing code. This sizing code contained models to account for coatings fasteners, adhesives, and strain isolation pads. Atmospheric entry heating profiles for two vehicles, the Access to Space (ATS) vehicle and a proposed Reusable Launch Vehicle (RLV), were used to ensure that the trends were not unique to a certain trajectory. Ten TPS concepts were compared for a range of applied heat loads and substructural heat capacities to identify general trends. This study found the blanket TPS concepts have the lightest weights over the majority of their applicable ranges, and current technology ceramic tiles and metallic TPS concepts have similar weights. A proposed, state-of-the-art metallic system which uses a higher temperature alloy and efficient multilayer insulation was predicted to be significantly lighter than the ceramic tile stems and approaches blanket TPS weights for higher integrated heat loads.

  4. Advanced Ceramics Property Measurements

    NASA Technical Reports Server (NTRS)

    Salem, Jonathan; Helfinstine, John; Quinn, George; Gonczy, Stephen

    2013-01-01

    Mechanical and physical properties of ceramic bodies can be difficult to measure correctly unless the proper techniques are used. The Advanced Ceramics Committee of ASTM, C-28, has developed dozens of consensus test standards and practices to measure various properties of a ceramic monolith, composite, or coating. The standards give the "what, how, how not, and why" for measurement of many mechanical, physical, thermal, and performance properties. Using these standards will provide accurate, reliable, and complete data for rigorous comparisons with other test results from your test lab, or another. The C-28 Committee has involved academics, producers, and users of ceramics to write and continually update more than 45 standards since the committee's inception in 1986. Included in this poster is a pictogram of the C-28 standards and information on how to obtain individual copies with full details or the complete collection of standards in one volume.

  5. Ceramic applications in the advanced Stirling automotive engine

    NASA Technical Reports Server (NTRS)

    Tomazic, W. A.; Cairelli, J. E.

    1977-01-01

    The ideal cycle, its application to a practical machine, and the specific advantages of high efficiency, low emissions, multi-fuel capability, and low noise of the stirling engine are discussed. Certain portions of the Stirling engine must operate continuously at high temperature. Ceramics offer the potential of cost reduction and efficiency improvement for advanced engine applications. Potential applications for ceramics in Stirling engines, and some of the special problems pertinent to using ceramics in the Stirling engine are described. The research and technology program in ceramics which is planned to support the development of advanced Stirling engines is outlined.

  6. Influence of temporary organic bond nature on the properties of compacts and ceramics

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

    Ditts, A., E-mail: ditts@tpu.ru; Revva, I., E-mail: revva@tpu.ru; Pogrebenkov, V.

    2016-01-15

    This work contains results of investigation of obtaining high thermally conductive ceramics from commercial powders of aluminum nitride and yttrium oxide by the method of monoaxial compaction of granulate. The principal scheme of preparation is proposed and technological properties of granulate are defined. Compaction conditions for simple items to use as heat removal in microelectronics and power electrical engineering have been established. Investigations of thermophysical properties of obtained ceramics and its structure by the XRD and SEM methods have been carried out. Ceramics with thermal conductivity from 172 to 174 W/m·K has been obtained as result of this work.

  7. Ceramic electrolyte coating and methods

    DOEpatents

    Seabaugh, Matthew M [Columbus, OH; Swartz, Scott L [Columbus, OH; Dawson, William J [Dublin, OH; McCormick, Buddy E [Dublin, OH

    2007-08-28

    Aqueous coating slurries useful in depositing a dense coating of a ceramic electrolyte material (e.g., yttrium-stabilized zirconia) onto a porous substrate of a ceramic electrode material (e.g., lanthanum strontium manganite or nickel/zirconia) and processes for preparing an aqueous suspension of a ceramic electrolyte material and an aqueous spray coating slurry including a ceramic electrolyte material. The invention also includes processes for depositing an aqueous spray coating slurry including a ceramic electrolyte material onto pre-sintered, partially sintered, and unsintered ceramic substrates and products made by this process.

  8. Ceramic Laser Materials

    PubMed Central

    Sanghera, Jasbinder; Kim, Woohong; Villalobos, Guillermo; Shaw, Brandon; Baker, Colin; Frantz, Jesse; Sadowski, Bryan; Aggarwal, Ishwar

    2012-01-01

    Ceramic laser materials have come a long way since the first demonstration of lasing in 1964. Improvements in powder synthesis and ceramic sintering as well as novel ideas have led to notable achievements. These include the first Nd:yttrium aluminum garnet (YAG) ceramic laser in 1995, breaking the 1 KW mark in 2002 and then the remarkable demonstration of more than 100 KW output power from a YAG ceramic laser system in 2009. Additional developments have included highly doped microchip lasers, ultrashort pulse lasers, novel materials such as sesquioxides, fluoride ceramic lasers, selenide ceramic lasers in the 2 to 3 μm region, composite ceramic lasers for better thermal management, and single crystal lasers derived from polycrystalline ceramics. This paper highlights some of these notable achievements. PMID:28817044

  9. Bioactivity of Y2O3 and CeO2 doped SiO2-SrO-Na2O glass-ceramics.

    PubMed

    Placek, L M; Keenan, T J; Wren, A W

    2016-08-01

    The bioactivity of yttrium and cerium are investigated when substituted for Sodium (Na) in a 0.52SiO2-0.24SrO-0.24-xNa2O-xMO glass-ceramics (where x = 0.08 and MO = Y2O3 or CeO2). Bioactivity is monitored through pH and inductively coupled plasma-optical emission spectrometry where pH of simulated body fluid ranged from 7.5 to 7.6 and increased between 8.2 and 10.0 after 14-day incubation with the glass-ceramic disks. Calcium (Ca) and phosphorus (P) levels in simulated body fluid after incubation with yttrium and cerium containing disks show a continual decline over the 14-day period. In contrast, Con disks (not containing yttrium or cerium) caused the elimination of Ca in solution after 1 day and throughout the incubation period, and initially showed a decline in P levels followed by an increase at 14 days. Scanning electron microscopy and energy dispersive spectroscopy confirmed the presence of Ca and P on the surface of the simulated body fluid-incubated disks and showed precipitates on Con and HCe (8 mol% cerium) samples. Cell viability of MC3T3 osteoblasts was not significantly affected at a 9% extract concentration. Optical microscopy after 24 h cell incubation with disks showed that Con samples do not support osteoblast or Schwann cell growth, while all yttrium and cerium containing disks have direct contact with osteoblasts spread across the wells. Schwann cells attached in all wells, but only showed spreading with the HY-S (8 mol% yttrium, heated to sintering temperature) and YCe (4 mol% yttrium and cerium) disks. Scanning electron microscopy of the compatible disks shows osteoblast and sNF96.2 Schwann cells attachment and spreading directly on the disk surfaces. © The Author(s) 2016.

  10. Environment Conscious Ceramics (Ecoceramics): An Eco-Friendly Route to Advanced Ceramic Materials

    NASA Technical Reports Server (NTRS)

    Singh, M.

    2001-01-01

    Environment conscious ceramics (Ecoceramics) are a new class of materials, which can be produced with renewable natural resources (wood) or wood wastes (wood sawdust). This technology provides an eco-friendly route to advanced ceramic materials. Ecoceramics have tailorable properties and behave like ceramic materials manufactured by conventional approaches. Silicon carbide-based ecoceramics have been fabricated by reactive infiltration of carbonaceous preforms by molten silicon or silicon-refractory metal alloys. The fabrication approach, microstructure, and mechanical properties of SiC-based ecoceramics are presented.

  11. Electric field tuning of magnetism in heterostructure of yttrium iron garnet film/lead magnesium niobate-lead zirconate titanate ceramic

    NASA Astrophysics Data System (ADS)

    Lian, Jianyun; Ponchel, Freddy; Tiercelin, Nicolas; Chen, Ying; Rémiens, Denis; Lasri, Tuami; Wang, Genshui; Pernod, Philippe; Zhang, Wenbin; Dong, Xianlin

    2018-04-01

    In this paper, the converse magnetoelectric (CME) effect by electric field tuning of magnetization in an original heterostructure composed of a polycrystalline yttrium iron garnet (YIG) film and a lead magnesium niobate-lead zirconate titanate (PMN-PZT) ceramic is presented. The magnetic performances of the YIG films with different thicknesses under a DC electric field applied to the PMN-PZT ceramics and a bias magnetic field are investigated. All the magnetization-electric field curves are found to be in good agreement with the butterfly like strain curve of the PMN-PZT ceramic. Both the sharp deformation of about 2.5‰ of PMN-PZT and the easy magnetization switching of YIG are proposed to be the reasons for the strongest CME interaction in the composite at the small electric coercive field of PMN-PZT (4.1 kV/cm) and the small magnetic coercive field of YIG (20 Oe) where the magnetic susceptibility reaches its maximum value. A remarkable CME coefficient of 3.1 × 10-7 s/m is obtained in the system with a 600 nm-thick YIG film. This heterostructure combining multiferroics and partially magnetized ferrite concepts is able to operate under a small or even in the absence of an external bias magnetic field and is more compact and power efficient than the traditional magnetoelectric devices.

  12. Ceramics containing dispersants for improved fracture toughness

    DOEpatents

    Nevitt, Michael V.; Aldred, Anthony T.; Chan, Sai-Kit

    1987-07-07

    The invention is a ceramic composition containing a new class of dispersant for hindering crack propagation by means of one or more energy-dissipative mechanisms. The composition is composed of a ceramic matrix with dispersed particles of a transformation-prone rare-earth niobate, tantalate or mixtures of these with each other and/or with a rare-earth vanadate. The dispersants, having a generic composition tRMO.sub.4, where R is a rare-earth element, B is Nb or Ta and O is oxygen, are mixed in powder form with a powder of the matrix ceramic and sintered to produce a ceramic form or body. The crack-hindering mechanisms operates to provide improved performance over a wide range of temperature and operating conditions.

  13. Ceramics containing dispersants for improved fracture toughness

    DOEpatents

    Nevitt, Michael V.; Aldred, Anthony T.; Chan, Sai-Kit

    1987-01-01

    The invention is a ceramic composition containing a new class of dispersant for hindering crack propagation by means of one or more energy-dissipative mechanisms. The composition is composed of a ceramic matrix with dispersed particles of a transformation-prone rare-earth niobate, tantalate or mixtures of these with each other and/or with a rare-earth vanadate. The dispersants, having a generic composition tRMO.sub.4, where R is a rare-earth element, B is Nb or Ta and O is oxygen, are mixed in powder form with a powder of the matrix ceramic and sintered to produce a ceramic form or body. The crack-hindering mechanisms operates to provide improved performance over a wide range of temperature and operating conditions.

  14. Recent Advances on Carbon Nanotubes and Graphene Reinforced Ceramics Nanocomposites

    PubMed Central

    Ahmad, Iftikhar; Yazdani, Bahareh; Zhu, Yanqiu

    2015-01-01

    Ceramics suffer the curse of extreme brittleness and demand new design philosophies and novel concepts of manufacturing to overcome such intrinsic drawbacks, in order to take advantage of most of their excellent properties. This has been one of the foremost challenges for ceramic material experts. Tailoring the ceramics structures at nanometre level has been a leading research frontier; whilst upgrading via reinforcing ceramic matrices with nanomaterials including the latest carbon nanotubes (CNTs) and graphene has now become an eminent practice for advanced applications. Most recently, several new strategies have indeed improved the properties of the ceramics/CNT nanocomposites, such as by tuning with dopants, new dispersions routes and modified sintering methods. The utilisation of graphene in ceramic nanocomposites, either as a solo reinforcement or as a hybrid with CNTs, is the newest development. This article will summarise the recent advances, key difficulties and potential applications of the ceramics nanocomposites reinforced with CNTs and graphene. PMID:28347001

  15. Development in laser peening of advanced ceramics

    NASA Astrophysics Data System (ADS)

    Shukla, Pratik; Smith, Graham C.; Waugh, David G.; Lawrence, Jonathan

    2015-07-01

    Laser peening is a well-known process applicable to surface treat metals and alloys in various industrial sectors. Research in the area of laser peening of ceramics is still scarce and a complete laser-ceramic interaction is still unreported. This paper focuses on laser peening of SiC ceramics employed for cutting tools, armor plating, dental and biomedical implants, with a view to elucidate the unreported work. A detailed investigation was conducted with 1064nm Nd:YAG ns pulse laser to first understand the surface effects, namely: the topography, hardness, KIc and the microstructure of SiC advanced ceramics. The results showed changes in surface roughness and microstructural modification after laser peening. An increase in surface hardness was found by almost 2 folds, as the diamond footprints and its flaws sizes were considerably reduced, thus, enhancing the resistance of SiC to better withstand mechanical impact. This inherently led to an enhancement in the KIc by about 42%. This is attributed to an induction of compressive residual stress and phase transformation. This work is a first-step towards the development of a 3-dimensional laser peening technique to surface treat many advanced ceramic components. This work has shown that upon tailoring the laser peening parameters may directly control ceramic topography, microstructure, hardness and the KIc. This is useful for increasing the performance of ceramics used for demanding applications particularly where it matters such as in military. Upon successful peening of bullet proof vests could result to higher ballistic strength and resistance against higher sonic velocity, which would not only prevent serious injuries, but could also help to save lives of soldiers on the battle fields.

  16. Application of scanning acoustic microscopy to advanced structural ceramics

    NASA Technical Reports Server (NTRS)

    Vary, Alex; Klima, Stanley J.

    1987-01-01

    A review is presentod of research investigations of several acoustic microscopy techniques for application to structural ceramics for advanced heat engines. Results obtained with scanning acoustic microscopy (SAM), scanning laser acoustic microscopy (SLAM), scanning electron acoustic microscopy (SEAM), and photoacoustic microscopy (PAM) are compared. The techniques were evaluated on research samples of green and sintered monolithic silicon nitrides and silicon carbides in the form of modulus-of-rupture bars containing deliberately introduced flaws. Strengths and limitations of the techniques are described with emphasis on statistics of detectability of flaws that constitute potential fracture origins.

  17. Advanced Ceramics Property and Performance Measurements

    NASA Technical Reports Server (NTRS)

    Jenkins, Michael; Salem, Jonathan; Helfinstine, John; Quinn, George; Gonczy, Stephen

    2015-01-01

    Mechanical and physical properties of ceramic bodies can be difficult to measure correctly unless the proper techniques are used. The Advanced Ceramics Committee of ASTM, C-28, has developed dozens of consensus test standards and practices to measure various properties of a ceramic monolith, composite, or coating. The standards give the what, how, how not, and why for measurement of many mechanical, physical, thermal, and performance properties. Using these standards will provide accurate, reliable, and complete data for rigorous comparisons with other test results from your test lab, or another. The C-28 Committee has involved academics, producers, and users of ceramics to write and continually update more than 45 standards since the committees inception in 1986. Included in this poster is a pictogram of the C-28 standards and information on how to obtain individual copies with full details or the complete collection of all of the standards in one volume.

  18. Advanced Ceramic Materials for Future Aerospace Applications

    NASA Technical Reports Server (NTRS)

    Misra, Ajay

    2015-01-01

    With growing trend toward higher temperature capabilities, lightweight, and multifunctionality, significant advances in ceramic matrix composites (CMCs) will be required for future aerospace applications. The presentation will provide an overview of material requirements for future aerospace missions, and the role of ceramics and CMCs in meeting those requirements. Aerospace applications will include gas turbine engines, aircraft structure, hypersonic and access to space vehicles, space power and propulsion, and space communication.

  19. Thermal expansion of ceramic samples containing natural zeolite

    NASA Astrophysics Data System (ADS)

    Sunitrová, Ivana; Trník, Anton

    2017-07-01

    In this study the thermal expansion of ceramic samples made from natural zeolite is investigated. Samples are prepared from the two most commonly used materials in ceramic industry (kaolin and illite). The first material is Sedlec kaolin from Czech Republic, which contains more than 90 mass% of mineral kaolinite. The second one is an illitic clay from Tokaj area in Hungary, which contains about 80 mass% of mineral illite. Varying amount of the clay (0 % - 50 %) by a natural zeolite from Nižný Hrabovec (Slovak Republic), containing clinoptilolite as major mineral phase is replaced. The measurements are performed on cylindrical samples with a diameter 14 mm and a length about 35 mm by a horizontal push - rod dilatometer. Samples made from pure kaolin, illite and zeolite are also subjected to this analysis. The temperature regime consists from linear heating rate of 5 °C/min from 30 °C to 1100 °C. The results show that the relative shrinkage of ceramic samples increases with amount of zeolite in samples.

  20. Robust Joining and Integration of Advanced Ceramics and Composites: Challenges, Opportunities, and Realities

    NASA Technical Reports Server (NTRS)

    Singh, Mrityunjay

    2006-01-01

    Advanced ceramics and fiber reinforced composites are under active consideration for use in a wide variety of high temperature applications within the aeronautics, space transportation, energy, and nuclear industries. The engineering designs of ceramic and composite components require fabrication and manufacturing of large and complex shaped parts of various thicknesses. In many instances, it is more economical to build up complex shapes by joining simple geometrical shapes. In addition, these components have to be joined or assembled with metallic sub-components. Thus, joining and attachment have been recognized as enabling technologies for successful utilization of ceramic components in various demanding applications. In this presentation, various challenges and opportunities in design, fabrication, and testing of high temperature joints in advanced ceramics and ceramic matrix composites will be presented. Silicon carbide based advanced ceramics and fiber reinforced composites in different shapes and sizes, have been joined using an affordable, robust ceramic joining technology. In addition, some examples of metal-ceramic brazing will also be presented. Microstructure and high temperature mechanical properties of joints in silicon carbide ceramics and composites will be reported. Various joint design philosophies and design issues in joining of ceramics and composites will be discussed.

  1. Boron-containing organosilane polymers and ceramic materials thereof

    NASA Technical Reports Server (NTRS)

    Riccitiello, Salvatore R. (Inventor); Hsu, Ming-Ta S. (Inventor); Chen, Timothy S. (Inventor)

    1988-01-01

    The present invention relates to organic silicon-boron polymers which upon pyrolysis produce high-temperature ceramic materials. More particularly, it relates to the polyorganoborosilanes containing -Si-B- bonds which generate high-temperature ceramic materials (e.g., SiC, SiB4, B4C) upon thermal degradation. The process for preparing these organic silicon-boron polymer precursors are also part of the invention.

  2. New ceramics containing dispersants for improved fracture toughness

    DOEpatents

    Nevitt, M.V.; Aldred, A.T.; Chan, Sai-Kit

    1985-07-01

    The invention is a ceramic composition containing a new class of dispersant for hindering crack propagation by means of one or more energy-dissipative mechanisms. The composition is composed of a ceramic matrix with dispersed particles of a transformation-prone rare-earth niobate, tantalate or mixtures of these with each other and/or with a rare-earth vanadate. The dispersants, having a generic composition tRBO/sub 4/, where R is a rare-earth element, B if Nb or Ta and O is oxygen, are mixed in powder form with a powder of the matrix ceramic and sintered to produce a ceramic form or body. The crack-hindering mechanisms operates to provide improved performance over a wide range of temperature and operating conditions.

  3. Polishing of silicon based advanced ceramics

    NASA Astrophysics Data System (ADS)

    Klocke, Fritz; Dambon, Olaf; Zunke, Richard; Waechter, D.

    2009-05-01

    Silicon based advanced ceramics show advantages in comparison to other materials due to their extreme hardness, wear and creep resistance, low density and low coefficient of thermal expansion. As a matter of course, machining requires high efforts. In order to reach demanded low roughness for optical or tribological applications a defect free surface is indispensable. In this paper, polishing of silicon nitride and silicon carbide is investigated. The objective is to elaborate scientific understanding of the process interactions. Based on this knowledge, the optimization of removal rate, surface quality and form accuracy can be realized. For this purpose, fundamental investigations of polishing silicon based ceramics are undertaken and evaluated. Former scientific publications discuss removal mechanisms and wear behavior, but the scientific insight is mainly based on investigations in grinding and lapping. The removal mechanisms in polishing are not fully understood due to complexity of interactions. The role of, e.g., process parameters, slurry and abrasives, and their influence on the output parameters is still uncertain. Extensive technological investigations demonstrate the influence of the polishing system and the machining parameters on the stability and the reproducibility. It is shown that the interactions between the advanced ceramics and the polishing systems is of great relevance. Depending on the kind of slurry and polishing agent the material removal mechanisms differ. The observed effects can be explained by dominating mechanical or chemo-mechanical removal mechanisms. Therefore, hypotheses to state adequate explanations are presented and validated by advanced metrology devices, such as SEM, AFM and TEM.

  4. EPR of radiation defects in lithium-oxyfluoride glass ceramics

    NASA Astrophysics Data System (ADS)

    Fedotovs, A.; Rogulis, U.; Sarakovskis, A.; Dimitrocenko, L.

    2010-11-01

    We studied oxyfluoride composites based on lithium silicate glasses with yttrium fluorides and rare-earth dopants. The electron paramagnetic resonance (EPR) has been used to obtain information about radiation induced defects in these materials. Spectra have been measured before and after X-ray irradiation at room temperature and at liquid nitrogen temperature. Fluoride crystallites within samples were created by means of thermal treatment at specific temperatures. EPR spectra of radiation induced defects in oxyfluoride glass ceramics, in which crystallites have not been yet created, show no explicit hfs interaction of fluorine nuclei. However, in glass ceramics, which already contains fluoride crystallites, the hfs characteristic to fluorine nuclei appears in the EPR spectra. EPR hyperfine structure could be explained within a model of an F-type centre in YF3 crystalline phase.

  5. ASTM Committee C28: International Standards for Properties and Performance of Advanced Ceramics-Three Decades of High-Quality, Technically-Rigorous Normalization

    NASA Technical Reports Server (NTRS)

    Jenkins, Michael G.; Salem, Jonathan A.

    2016-01-01

    Physical and mechanical properties and performance of advanced ceramics and glasses are difficult to measure correctly without the proper techniques. For over three decades, ASTM Committee C28 on Advanced Ceramics, has developed high-quality, technically-rigorous, full-consensus standards (e.g., test methods, practices, guides, terminology) to measure properties and performance of monolithic and composite ceramics that may be applied to glasses in some cases. These standards contain testing particulars for many mechanical, physical, thermal, properties and performance of these materials. As a result these standards are used to generate accurate, reliable, repeatable and complete data. Within Committee C28, users, producers, researchers, designers, academicians, etc. have written, continually updated, and validated through round-robin test programs, 50 standards since the Committee's founding in 1986. This paper provides a detailed retrospective of the 30 years of ASTM Committee C28 including a graphical pictogram listing of C28 standards along with examples of the tangible benefits of standards for advanced ceramics to demonstrate their practical applications.

  6. Ceramic components for MHD electrode

    DOEpatents

    Marchant, D.D.

    A ceramic component which exhibits electrical conductivity down to near room temperatures has the formula: Hf/sub x/In/sub y/A/sub z/O/sub 2/ where x = 0.1 to 0.4, y = 0.3 to 0.6, z = 0.1 to 0.4 and A is a lanthanide rare earth or yttrium. The component is suitable for use in the fabrication of MHD electrodes or as the current leadout portion of a composite electrode with other ceramic components.

  7. Ceramic Integration Technologies for Advanced Energy Systems: Critical Needs, Technical Challenges, and Opportunities

    NASA Technical Reports Server (NTRS)

    Singh, Mrityunjay

    2010-01-01

    Advanced ceramic integration technologies dramatically impact the energy landscape due to wide scale application of ceramics in all aspects of alternative energy production, storage, distribution, conservation, and efficiency. Examples include fuel cells, thermoelectrics, photovoltaics, gas turbine propulsion systems, distribution and transmission systems based on superconductors, nuclear power generation and waste disposal. Ceramic integration technologies play a key role in fabrication and manufacturing of large and complex shaped parts with multifunctional properties. However, the development of robust and reliable integrated systems with optimum performance requires the understanding of many thermochemical and thermomechanical factors, particularly for high temperature applications. In this presentation, various needs, challenges, and opportunities in design, fabrication, and testing of integrated similar (ceramic ceramic) and dissimilar (ceramic metal) material www.nasa.gov 45 ceramic-ceramic-systems have been discussed. Experimental results for bonding and integration of SiC based Micro-Electro-Mechanical-Systems (MEMS) LDI fuel injector and advanced ceramics and composites for gas turbine applications are presented.

  8. Evidence of yttrium silicate inclusions in YSZ-porcelain veneers.

    PubMed

    Stoner, Brian R; Griggs, Jason A; Neidigh, John; Piascik, Jeffrey R

    2014-04-01

    This report introduces the discovery of crystalline defects that can form in the porcelain veneering layer when in contact with yttria-stabilized zirconia (YSZ). The focus was on dental prostheses and understanding the defects that form in the YSZ/porcelain system; however the data reported herein may have broader implications toward the use and stability of YSZ-based ceramics in general. Specimens were cut from fully sintered YSZ plates and veneering porcelain was applied (<1 mm thick) to one surface and fired under manufacturer's recommended protocol. Scanning electron microscopy (SEM) with integrated electron dispersive X-ray (EDAX) was used for microstructural and elemental analysis. EDAX, for chemical analysis and transmission electron diffraction (TED) for structural analysis were both performed in the transmission electron microscope (TEM). Additionally, in order to spatially resolve Y-rich precipitates, micro-CT scans were conducted at varying depths within the porcelain veneer. Local EDAX (SEM) was performed in the regions of visible inclusions and showed significant increases in yttrium concentration. TEM specimens also showed apparent inclusions in the porcelain and selected area electron diffraction was performed on these regions and found the inclusions to be crystalline and identified as either yttrium-silicate (Y2 SiO5 ) or yttrium-disilicate (Y2 Si2 O7 ). Micro-CT data showed that yttrium-silicate precipitates were distributed throughout the thickness of the porcelain veneer. Future studies are needed to determine whether many of the premature failures associated with this materials system may be the result of crystalline flaws that form as a result of high temperature yttrium diffusion near the surfaces of YSZ. © 2013 Wiley Periodicals, Inc.

  9. Innovative grinding wheel design for cost-effective machining of advanced ceramics

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

    Licht, R.H.; Kuo, P.; Liu, S.

    2000-05-01

    This Final Report covers the Phase II Innovative Grinding Wheel (IGW) program in which Norton Company successfully developed a novel grinding wheel for cost-effective cylindrical grinding of advanced ceramics. In 1995, Norton Company successfully completed the 16-month Phase I technical effort to define requirements, design, develop, and evaluate a next-generation grinding wheel for cost-effective cylindrical grinding of advanced ceramics using small prototype wheels. The Phase II program was initiated to scale-up the new superabrasive wheel specification to larger diameters, 305-mm to 406-mm, required for most production grinding of cylindrical ceramic parts, and to perform in-house and independent validation grinding tests.

  10. Standardization Efforts for Mechanical Testing and Design of Advanced Ceramic Materials and Components

    NASA Technical Reports Server (NTRS)

    Salem, Jonathan A.; Jenkins, Michael G.

    2003-01-01

    Advanced aerospace systems occasionally require the use of very brittle materials such as sapphire and ultra-high temperature ceramics. Although great progress has been made in the development of methods and standards for machining, testing and design of component from these materials, additional development and dissemination of standard practices is needed. ASTM Committee C28 on Advanced Ceramics and ISO TC 206 have taken a lead role in the standardization of testing for ceramics, and recent efforts and needs in standards development by Committee C28 on Advanced Ceramics will be summarized. In some cases, the engineers, etc. involved are unaware of the latest developments, and traditional approaches applicable to other material systems are applied. Two examples of flight hardware failures that might have been prevented via education and standardization will be presented.

  11. PREFACE: Symposium 1: Advanced Structure Analysis and Characterization of Ceramic Materials

    NASA Astrophysics Data System (ADS)

    Yashima, Masatomo

    2011-05-01

    Preface to Symposium 1 (Advanced Structure Analysis and Characterization of Ceramic Materials) of the International Congress of Ceramics III, held 14-18 November 2010 in Osaka, Japan Remarkable developments have been made recently in the structural analysis and characterization of inorganic crystalline and amorphous materials, such as x-ray, neutron, synchrotron and electron diffraction, x-ray/neutron scattering, IR/Raman scattering, NMR, XAFS, first-principle calculations, computer simulations, Rietveld analysis, the maximum-entropy method, in situ measurements at high temperatures/pressures and electron/nuclear density analysis. These techniques enable scientists to study not only static and long-range periodic structures but also dynamic and short-/intermediate-range structures. Multi-scale characterization from the electron to micrometer levels is becoming increasingly important as a means of understanding phenomena at the interfaces, grain boundaries and surfaces of ceramic materials. This symposium has discussed the structures and structure/property relationships of various ceramic materials (electro, magnetic and optical ceramics; energy and environment related ceramics; bio-ceramics; ceramics for reliability secure society; traditional ceramics) through 38 oral presentations including 8 invited lectures and 49 posters. Best poster awards were given to six excellent poster presentations (Y-C Chen, Tokyo Institute of Technology; C-Y Chung, Tohoku University; T Stawski, University of Twente; Y Hirano, Nagoya Institute of Technology; B Bittova, Charles University Prague; Y Onodera, Kyoto University). I have enjoyed working with my friends in the ICC3 conference. I would like to express special thanks to other organizers: Professor Scott T Misture, Alfred University, USA, Professor Xiaolong Chen, Institute of Physics, CAS, China, Professor Takashi Ida, Nagoya Institute of Technology, Japan, Professor Isao Tanaka, Kyoto University, Japan. I also acknowledge the

  12. Challenges and Opportunities in Reactive Processing and Applications of Advanced Ceramic Materials

    NASA Technical Reports Server (NTRS)

    Singh, Mrityunjay

    2003-01-01

    Recently, there has been a great deal of interest in the research, development, and commercialization of innovative synthesis and processing technologies for advanced ceramics and composite materials. Reactive processing approaches have been actively considered due to their robustness, flexibility, and affordability. A wide variety of silicon carbide-based advanced ceramics and composites are currently being fabricated using the processing approaches involving reactive infiltration of liquid and gaseous species into engineered fibrous or microporous carbon performs. The microporous carbon performs have been fabricated using the temperature induced phase separation and pyrolysis of two phase organic (resin-pore former) mixtures and fiber reinforcement of carbon and ceramic particulate bodies. In addition, pyrolyzed native plant cellulose tissues also provide unique carbon templates for manufacturing of non-oxide and oxide ceramics. In spite of great interest in this technology due to their affordability and robustness, there is a lack of scientific basis for process understanding and many technical challenges still remain. The influence of perform properties and other parameters on the resulting microstructure and properties of final material is not well understood. In this presentation, mechanism of silicon-carbon reaction in various systems and the effect of perform microstructure on the mechanical properties of advanced silicon carbide based materials will be discussed. Various examples of applications of reactively processed advanced silicon carbide ceramics and composite materials will be presented.

  13. Ceramic Technology for Advanced Heat Engines Project. Semiannual progress report, October 1984-March 1985

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

    Not Available

    1985-09-01

    A five-year project plan was developed with extensive input from private industry. The objective of the project is to develop the industrial technology base required for reliable ceramics for application in advanced automotive heat engines. The project approach includes determining the mechanisms controlling reliability, improving processes for fabricating existing ceramics, developing new materials with increased reliability, and testing these materials in simulated engine environments to confirm reliability. Although this is a generic materials project, the focus is on structural ceramics for advanced gas turbine and diesel engines, ceramic bearings and attachments, and ceramic coatings for thermal barrier and wear applicationsmore » in these engines.« less

  14. Ceramic technology for advanced heat engines project. Semiannual progress report, April-September 1985

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

    Not Available

    1986-05-01

    An assessment of needs was completed, and a five-year project plan was developed with input from private industry. Objective is to develop the industrial technology base required for reliable ceramics for application in advanced automotive heat engines. Focus is on 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. The work described in this report is organized according to the following WBS project elements: management and coordination; materials and processing (monolithics, ceramic composites, thermal and wear coatings, joining); materials design methodology (contact interfaces, newmore » concepts); data base and life prediction (time-dependent behavior, environmental effects, fracture mechanics, NDE development); and technology transfer. This report includes contributions from all currently active project participants.« less

  15. Ceramic technology for advanced heat engines project. Semiannual progress report, October 1985-March 1986

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

    Not Available

    1986-08-01

    Significant accomplishments in fabricating cermaic components for the Department of Energy (DOE), National Aeronautics and Space Administration (NASA), and Department of Defense (DOD) advanced heat engine programs have provided evidence that the operation of ceramic parts in high-temperature engine environments is feasible. However, additional research is needed in materials and processing development, design methodology, and data base and life prediction. An assessment of needs was completed, and a five-year project plan was developed with extensive input from private industry. The objective of the project is to develop the industrial technology base required for reliable ceramics for application in advanced automotivemore » 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 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.« less

  16. A review on the advances in 3D printing and additive manufacturing of ceramics and ceramic matrix composites for optical applications

    NASA Astrophysics Data System (ADS)

    Goodman, William A.

    2017-09-01

    This paper provides a review of advances in 3D printing and additive manufacturing of ceramic and ceramic matrix composites for optical applications. Dr. Goodman has been pioneering additive manufacturing of ceramic matrix composites since 2008. He is the inventor of HoneySiC material, a zero-CTE additively manufactured carbon fiber reinforced silicon carbide ceramic matrix composite, briefly mentioned here. More recently Dr. Goodman has turned his attention to the direct printing of ceramics for optical applications via various techniques including slurry and laser sintering of silicon carbide and other ceramic materials.

  17. International Standards for Properties and Performance of Advanced Ceramics - 30 years of Excellence

    NASA Technical Reports Server (NTRS)

    Jenkins, Michael G.; Salem, Jonathan A.; Helfinstine, John; Quinn, George D.; Gonczy, Stephen T.

    2016-01-01

    Mechanical and physical properties/performance of brittle bodies (e.g., advanced ceramics and glasses) can be difficult to measure correctly unless the proper techniques are used. For three decades, ASTM Committee C28 on Advanced Ceramics, has developed numerous full-consensus standards (e.g., test methods, practices, guides, terminology) to measure various properties and performance of a monolithic and composite ceramics and coatings that, in some cases, may be applicable to glasses. These standards give the "what, how, how not, why, why not, etc." for many mechanical, physical, thermal, properties and performance of advanced ceramics. Use of these standards provides accurate, reliable, repeatable and complete data. Involvement in ASTM Committee C28 has included users, producers, researchers, designers, academicians, etc. who write, continually update, and validate through round robin test programmes, more than 45 standards in the 30 years since the Committee's inception in 1986. Included in this poster is a pictogram of the ASTM Committee C28 standards and how to obtain them either as i) individual copies with full details or ii) a complete collection in one volume. A listing of other ASTM committees of interest is included. In addition, some examples of the tangible benefits of standards for advanced ceramics are employed to demonstrate their practical application.

  18. Tungsten - Yttrium Based Nuclear Structural Materials

    NASA Astrophysics Data System (ADS)

    Ramana, Chintalapalle; Chessa, Jack; Martinenz, Gustavo

    2013-04-01

    The challenging problem currently facing the nuclear science community in this 21st century is design and development of novel structural materials, which will have an impact on the next-generation nuclear reactors. The materials available at present include reduced activation ferritic/martensitic steels, dispersion strengthened reduced activation ferritic steels, and vanadium- or tungsten-based alloys. These materials exhibit one or more specific problems, which are either intrinsic or caused by reactors. This work is focussed towards tungsten-yttrium (W-Y) based alloys and oxide ceramics, which can be utilized in nuclear applications. The goal is to derive a fundamental scientific understanding of W-Y-based materials. In collaboration with University of Califonia -- Davis, the project is designated to demonstrate the W-Y based alloys, ceramics and composites with enhanced physical, mechanical, thermo-chemical properties and higher radiation resistance. Efforts are focussed on understanding the microstructure, manipulating materials behavior under charged-particle and neutron irradiation, and create a knowledge database of defects, elemental diffusion/segregation, and defect trapping along grain boundaries and interfaces. Preliminary results will be discussed.

  19. Evaluation of biocompatibility of various ceramic powders with human fibroblasts in vitro.

    PubMed

    Li, J; Liu, Y; Hermansson, L; Söremark, R

    1993-01-01

    Cell reaction to powders of ceramics was studied in vitro. Cultured human fibroblasts were exposed to different types of ceramic powders: zirconia (ZP), alumina (A), tricalcium phosphate (TCP) and hydroxyapatite (HA), at various concentrations. The cell viability at the different exposure times was measured by the colony formation (expressed as colony forming efficiency, CFE), neutral red uptake (NR) and colorimetric tetrazolium (MTT) reduction. Alumina and hydroxyapatite showed no cytotoxic effects at studied doses (1-500 mug/ml) while zirconia and tricalcium phosphate inhibited cell viability, with 50% of CFE reduction at the concentration of about 50 mug/ml. In order to study the cytotoxic mechanism of zirconia powder, two further experiments were included, viz. the cellular response to the sintered zirconia ceramic powders (CZP) which were obtained by crushing the sintered ceramic material; and the measurement of the degradation of zirconia ceramic plate in the different solutions, i.e., either in saline or in 0.02 M lactic acid (pH 2.72). Similar cell reactions were obtained for the CZP and ZP by using MTT and NR assays. Slow releases of ions from zirconia ceramic plate, yttrium in both solutions and zirconium and yttrium in lactic acid, were detected.

  20. All-alkoxide synthesis of strontium-containing metal oxides

    DOEpatents

    Boyle, Timothy J.

    2001-01-01

    A method for making strontium-containing metal-oxide ceramic thin films from a precursor liquid by mixing a strontium neo-pentoxide dissolved in an amine solvent and at least one metal alkoxide dissolved in a solvent, said at least one metal alkoxide selected from the group consisting of alkoxides of calcium, barium, bismuth, cadmium, lead, titanium, tantalum, hafnium, tungsten, niobium, zirconium, yttrium, lanthanum, antimony, chromium and thallium, depositing a thin film of the precursor liquid on a substrate, and heating the thin film in the presence of oxygen at between 550 and 700.degree. C.

  1. Advanced Ceramics for NASA's Current and Future Needs

    NASA Technical Reports Server (NTRS)

    Jaskowiak, Martha H.

    2006-01-01

    Ceramic composites and monolithics are widely recognized by NASA as enabling materials for a variety of aerospace applications. Compared to traditional materials, ceramic materials offer higher specific strength which can enable lighter weight vehicle and engine concepts, increased payloads, and increased operational margins. Additionally, the higher temperature capabilities of these materials allows for increased operating temperatures within the engine and on the vehicle surfaces which can lead to improved engine efficiency and vehicle performance. To meet the requirements of the next generation of both rocket and air-breathing engines, NASA is actively pursuing the development and maturation of a variety of ceramic materials. Anticipated applications for carbide, nitride and oxide-based ceramics will be presented. The current status of these materials and needs for future goals will be outlined. NASA also understands the importance of teaming with other government agencies and industry to optimize these materials and advance them to the level of maturation needed for eventual vehicle and engine demonstrations. A number of successful partnering efforts with NASA and industry will be highlighted.

  2. Strength and flexibility properties of advanced ceramic fabrics

    NASA Technical Reports Server (NTRS)

    Sawko, P. M.; Tran, H. K.

    1985-01-01

    The mechanical properties of four advanced ceramic fabrics were measured at a temperature range of 23C to 1200C. The fabrics evaluated were silica, high and low-boria content aluminoborosilicate, and silicon carbide. Properties studied included fabric break strengths from room temperature to 1200C, and bending durability after temperature conditioning at 1200C and 1400C. The interaction of the fabric and ceramic insulation was also studied for shrinkage, appearance, bend resistance, and fabric-to-insulation bonding. Based on these tests, the low-boria content aluminoborosilicate fabric retained more strength and fabric durability than the other fabrics studied at high temperature.

  3. Strength and flexibility properties of advanced ceramic fabrics

    NASA Technical Reports Server (NTRS)

    Sawko, P. M.; Tran, H. K.

    1985-01-01

    The mechanical properties of four advanced ceramic fabrics are measured at a temperature range of 23 C to 1200 C. The fabrics evaluated are silica, high-and low-boria content aluminoborosilicate, and silicon carbide. Properties studied include fabric break strengths from room temperature to 1200 C, and bending durability after temperature conditioning at 1200 C and 1400 C. The interaction of the fabric and ceramic insulation is also studied for shrinkage, appearance, bend resistance, and fabric-to-insulation bonding. Based on these tests, the low-boria content aluminoborosilicate fabric retains more strength and fabric durability than the other fabrics studied at high temperature.

  4. Wetting of single crystal mullite by borosilicate and yttrium-aluminosilicate glasses and wetting phenomena of steels containing aluminum and titanium

    NASA Astrophysics Data System (ADS)

    Eldred, Benjamin Todd

    This dissertation consists of two major sections. The first section concerns the wetting of single crystal mullite by borosilicate and yttrium-aluminosilicate glasses. The borosilicate glass showed poor wetting and interacted only moderately with the substrate. The yttrium-aluminosilicate glass interacted strongly with mullite and showed very good wetting. Balanced chemical equations between each glass and mullite were derived from EDS data. Wetting was found to be dependent on the crystallographic orientation of the substrate, in agreement with previous studies of the surface energy of mullite. The second section concerns the wetting phenomena of steels containing aluminum and titanium. A modified sessile drop technique was used to investigate the wetting of steels containing aluminum and/or titanium as a function of furnace atmosphere. It was found that the steel chemistry and furnace atmosphere had little effect on wetting except in the case of a particular ultra-low carbon steel containing both aluminum and titanium. This steel was found to show significantly lower contact angles than any other steel tested when it was in an atmosphere of pure hydrogen. As nitrogen was added to the atmosphere, the contact angle increased monotonically and irreversibly. The interaction between aluminum, titanium, and nitrogen is explained in terms of first-order interaction coefficients available in thermodynamic literature.

  5. Ceramic technology for advanced heat engines project: Semiannual progress report for April through September 1986

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

    Not Available

    1987-03-01

    An assessment of needs was completed, and a five-year project plan was developed with extensive input from private industry. 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 structural ceramics for advanced gas turbine and diesel engines, ceramic bearings and attachments, and ceramic coatings for thermal barriermore » and wear applications in these engines.« less

  6. Research on chemical vapor deposition processes for advanced ceramic coatings

    NASA Technical Reports Server (NTRS)

    Rosner, Daniel E.

    1993-01-01

    Our interdisciplinary background and fundamentally-oriented studies of the laws governing multi-component chemical vapor deposition (VD), particle deposition (PD), and their interactions, put the Yale University HTCRE Laboratory in a unique position to significantly advance the 'state-of-the-art' of chemical vapor deposition (CVD) R&D. With NASA-Lewis RC financial support, we initiated a program in March of 1988 that has led to the advances described in this report (Section 2) in predicting chemical vapor transport in high temperature systems relevant to the fabrication of refractory ceramic coatings for turbine engine components. This Final Report covers our principal results and activities for the total NASA grant of $190,000. over the 4.67 year period: 1 March 1988-1 November 1992. Since our methods and the technical details are contained in the publications listed (9 Abstracts are given as Appendices) our emphasis here is on broad conclusions/implications and administrative data, including personnel, talks, interactions with industry, and some known applications of our work.

  7. Development of 2024 AA-Yttrium composites by Spark Plasma Sintering

    NASA Astrophysics Data System (ADS)

    Vidyasagar, CH S.; Karunakar, D. B.

    2018-04-01

    The method of fabrication of MMNCs is quite a challenge, which includes advanced processing techniques like Spark Plasma Sintering (SPS), etc. The objective of the present work is to fabricate aluminium based MMNCs with the addition of small amounts of yttrium using Spark Plasma Sintering and to evaluate their mechanical and microstructure properties. Samples of 2024 AA with yttrium ranging from 0.1% to 0.5 wt% are fabricated by Spark Plasma Sintering (SPS). Hardness of the samples is determined using Vickers hardness testing machine. The metallurgical characterization of the samples is evaluated by Optical Microscopy (OM), Field Emission Scanning Electron Microscopy (FE-SEM). Unreinforced 2024 AA sample is also fabricated as a benchmark to compare its properties with those of the composite developed. It is found that the yttrium addition increases the above mentioned properties by altering the precipitation kinetics and intermetallic formation to some extent and then decreases gradually when yttrium wt% increases beyond 0.3 wt%. High density (˂ 99.75) is achieved in the samples and highest hardness achieved is 114 Hv, fabricated by spark plasma sintering and uniform distribution of yttrium is observed.

  8. Elevated Temperature Testing and Modeling of Advanced Toughened Ceramic Materials

    NASA Technical Reports Server (NTRS)

    Keith, Theo G.

    2005-01-01

    The purpose of this report is to provide a final report for the period of 12/1/03 through 11/30/04 for NASA Cooperative Agreement NCC3-776, entitled "Elevated Temperature Testing and Modeling of Advanced Toughened Ceramic Materials." During this final period, major efforts were focused on both the determination of mechanical properties of advanced ceramic materials and the development of mechanical test methodologies under several different programs of the NASA-Glenn. The important research activities made during this period are: 1. Mechanical properties evaluation of two gas-turbine grade silicon nitrides. 2) Mechanical testing for fuel-cell seal materials. 3) Mechanical properties evaluation of thermal barrier coatings and CFCCs and 4) Foreign object damage (FOD) testing.

  9. Advanced Gas Turbine (AGT) Technology Development Project, ceramic component developments

    NASA Technical Reports Server (NTRS)

    Teneyck, M. O.; Macbeth, J. W.; Sweeting, T. B.

    1987-01-01

    The ceramic component technology development activity conducted by Standard Oil Engineered Materials Company while performing as a principal subcontractor to the Garrett Auxiliary Power Division for the Advanced Gas Turbine (AGT) Technology Development Project (NASA Contract DEN3-167) is summarized. The report covers the period October 1979 through July 1987, and includes information concerning ceramic technology work categorized as common and unique. The former pertains to ceramic development applicable to two parallel AGT projects established by NASA contracts DEN3-168 (AGT100) and DEN3-167 (AGT101), whereas the unique work solely pertains to Garrett directed activity under the latter contract. The AGT101 Technology Development Project is sponsored by DOE and administered by NASA-Lewis. Standard Oil directed its efforts toward the development of ceramic materials in the silicon-carbide family. Various shape forming and fabrication methods, and nondestructive evaluation techniques were explored to produce the static structural components for the ceramic engine. This permitted engine testing to proceed without program slippage.

  10. Development of sensors for ceramic components in advanced propulsion systems: Survey and evaluation of measurement techniques for temperature, strain and heat flux for ceramic components in advanced propulsion systems

    NASA Technical Reports Server (NTRS)

    Atkinson, W. H.; Cyr, M. A.; Strange, R. R.

    1988-01-01

    The report presents the final results of Tasks 1 and 2, Development of Sensors for Ceramic Components in Advanced Propulsion Systems (NASA program NAS3-25141). During Task 1, an extensive survey was conducted of sensor concepts which have the potential for measuring surface temperature, strain and heat flux on ceramic components for advanced propulsion systems. Each sensor concept was analyzed and evaluated under Task 2; sensor concepts were then recommended for further development. For temperature measurement, both pyrometry and thermographic phosphors are recommended for measurements up to and beyond the melting point of ceramic materials. For lower temperature test programs, the thin-film techniques offer advantages in the installation of temperature sensors. Optical strain measurement techniques are recommended because they offer the possibility of being useful at very high temperature levels. Techniques for the measurement of heat flux are recommended for development based on both a surface mounted sensor and the measurement of the temperature differential across a portion of a ceramic component or metallic substrate.

  11. Dispersed metal-toughened ceramics and ceramic brazing

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

    Moorhead, A.J.; Tiegs, T.N.; Lauf, R.J.

    1983-01-01

    An alumina (Al/sub 2/O/sub 3/) based material that contains approximately 1 vol % finely dispersed platinum or chromium was developed for use in high temperature thermal-shock resistant electrical insulators. The work at ORNL is divided into two areas: (1) development of DMT ceramics; and (2) development of brazing filler metals suitable for making ceramic-to-ceramic and ceramic-to-metal brazements. The DMT ceramics and brazements are intended for service at elevated temperatures and at high stress levels in the dirty environments of advanced heat engines. The development and characterization of DMT ceramics includes processing (powder preparation, densification and heat treatment) and detailed measurementmore » of mechanical and physical properties (strength, fracture toughness, and thermal conductivity). The brazing work includes: (1) the formulation and melting of small quantities of experimental brazing filler metals; (2) evaluation of the wetting and bonding behavior of these filler metals on Al/sub 2/O/sub 3/, partially stabilized zirconia and ..cap alpha..-SiC in a sessile drop apparatus; and (3) determine the short-term strength and fracture toughness of brazements.« less

  12. 76 FR 23837 - Certain Ceramic Capacitors and Products Containing Same; Notice of the Commission's Final...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-04-28

    ... INTERNATIONAL TRADE COMMISSION [Investigation No. 337-TA-692] Certain Ceramic Capacitors and Products Containing Same; Notice of the Commission's Final Determination of No Violation of Section 337... ceramic capacitors and products containing the same by reason of infringement of various claims of United...

  13. Re{sup 3+} : YAG laser ceramics: synthesis, optical properties and laser characteristics

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

    Bagayev, S N; Vatnik, S M; Vedin, I A

    2015-05-31

    Highly transparent yttrium aluminium garnet ceramics doped with holmium or ytterbium or neodymium are synthesised. The ceramics were made of a mixture of nanopowders synthesised by laser ablation. The structural and spectral characteristics of ceramics are studied. In the samples with holmium Ho{sup 3+} and neodymium Nd{sup 3+} ions, lasing was achieved with a slope efficiency of 40% and 35.3%, respectively; the maximum laser power exceeded 4 W. The internal absorption and scattering losses for 1% Nd : YAG ceramics are estimated to be 1.6 × 10{sup -2} cm{sup -1}. (extreme light fields and their applications)

  14. Liquid-assisted laser ablation of advanced ceramics and glass-ceramic materials

    NASA Astrophysics Data System (ADS)

    Garcia-Giron, A.; Sola, D.; Peña, J. I.

    2016-02-01

    In this work, results obtained by laser ablation of advanced ceramics and glass-ceramic materials assisted by liquids are reported. A Q-switched Nd:YAG laser at its fundamental wavelength of 1064 nm with pulse-width in the nanosecond range was used to machine the materials, which were immersed in water and ethylene glycol. Variation in geometrical parameters, morphology, and ablation yields were studied by using the same laser working conditions. It was observed that machined depth and removed volume depended on the thermal, optical, and mechanical features of the processed materials as well as on the properties of the surrounding medium in which the laser processing was carried out. Variation in ablation yields was studied in function of the liquid used to assist the laser process and related to refractive index and viscosity. Material features and working conditions were also related to the obtained results in order to correlate ablation parameters with respect to the hardness of the processed materials.

  15. Ceramic Processing

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

    EWSUK,KEVIN G.

    1999-11-24

    Ceramics represent a unique class of materials that are distinguished from common metals and plastics by their: (1) high hardness, stiffness, and good wear properties (i.e., abrasion resistance); (2) ability to withstand high temperatures (i.e., refractoriness); (3) chemical durability; and (4) electrical properties that allow them to be electrical insulators, semiconductors, or ionic conductors. Ceramics can be broken down into two general categories, traditional and advanced ceramics. Traditional ceramics include common household products such as clay pots, tiles, pipe, and bricks, porcelain china, sinks, and electrical insulators, and thermally insulating refractory bricks for ovens and fireplaces. Advanced ceramics, also referredmore » to as ''high-tech'' ceramics, include products such as spark plug bodies, piston rings, catalyst supports, and water pump seals for automobiles, thermally insulating tiles for the space shuttle, sodium vapor lamp tubes in streetlights, and the capacitors, resistors, transducers, and varistors in the solid-state electronics we use daily. The major differences between traditional and advanced ceramics are in the processing tolerances and cost. Traditional ceramics are manufactured with inexpensive raw materials, are relatively tolerant of minor process deviations, and are relatively inexpensive. Advanced ceramics are typically made with more refined raw materials and processing to optimize a given property or combination of properties (e.g., mechanical, electrical, dielectric, optical, thermal, physical, and/or magnetic) for a given application. Advanced ceramics generally have improved performance and reliability over traditional ceramics, but are typically more expensive. Additionally, advanced ceramics are typically more sensitive to the chemical and physical defects present in the starting raw materials, or those that are introduced during manufacturing.« less

  16. Advanced Metals and Ceramics for Armor and Anti-Armor Applications. High-Fidelity Design and Processing of Advanced Armor Ceramics

    DTIC Science & Technology

    2007-06-01

    microstructures through advanced powder processing , (7) nondestructive evaluation of ceramic armor, (8) investigation of the relation between quasi-static...of a green microstructure of a compact prepared by this process using Superior Graphite 490 powder that had been twice beneficiated by settling and...create a dense, uniform microstructure of highly oriented grains • Determined the relationship between processing parameters, such as shear and solids

  17. Polymer, metal and ceramic matrix composites for advanced aircraft engine applications

    NASA Technical Reports Server (NTRS)

    Mcdanels, D. L.; Serafini, T. T.; Dicarlo, J. A.

    1985-01-01

    Advanced aircraft engine research within NASA Lewis is being focused on propulsion systems for subsonic, supersonic, and hypersonic aircraft. Each of these flight regimes requires different types of engines, but all require advanced materials to meet their goals of performance, thrust-to-weight ratio, and fuel efficiency. The high strength/weight and stiffness/weight properties of resin, metal, and ceramic matrix composites will play an increasingly key role in meeting these performance requirements. At NASA Lewis, research is ongoing to apply graphite/polyimide composites to engine components and to develop polymer matrices with higher operating temperature capabilities. Metal matrix composites, using magnesium, aluminum, titanium, and superalloy matrices, are being developed for application to static and rotating engine components, as well as for space applications, over a broad temperature range. Ceramic matrix composites are also being examined to increase the toughness and reliability of ceramics for application to high-temperature engine structures and components.

  18. Test Standard Developed for Determining the Slow Crack Growth of Advanced Ceramics at Ambient Temperature

    NASA Technical Reports Server (NTRS)

    Choi, Sung R.; Salem, Jonathan A.

    1998-01-01

    The service life of structural ceramic components is often limited by the process of slow crack growth. Therefore, it is important to develop an appropriate testing methodology for accurately determining the slow crack growth design parameters necessary for component life prediction. In addition, an appropriate test methodology can be used to determine the influences of component processing variables and composition on the slow crack growth and strength behavior of newly developed materials, thus allowing the component process to be tailored and optimized to specific needs. At the NASA Lewis Research Center, work to develop a standard test method to determine the slow crack growth parameters of advanced ceramics was initiated by the authors in early 1994 in the C 28 (Advanced Ceramics) committee of the American Society for Testing and Materials (ASTM). After about 2 years of required balloting, the draft written by the authors was approved and established as a new ASTM test standard: ASTM C 1368-97, Standard Test Method for Determination of Slow Crack Growth Parameters of Advanced Ceramics by Constant Stress-Rate Flexural Testing at Ambient Temperature. Briefly, the test method uses constant stress-rate testing to determine strengths as a function of stress rate at ambient temperature. Strengths are measured in a routine manner at four or more stress rates by applying constant displacement or loading rates. The slow crack growth parameters required for design are then estimated from a relationship between strength and stress rate. This new standard will be published in the Annual Book of ASTM Standards, Vol. 15.01, in 1998. Currently, a companion draft ASTM standard for determination of the slow crack growth parameters of advanced ceramics at elevated temperatures is being prepared by the authors and will be presented to the committee by the middle of 1998. Consequently, Lewis will maintain an active leadership role in advanced ceramics standardization within ASTM

  19. Simulation of Impact Phenomena on the Composite Structures Containing Ceramic Plates and High Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Geantă, V.; Cherecheș, T.; Lixandru, P.; Voiculescu, I.; Ștefănoiu, R.; Dragnea, D.; Zecheru, T.; Matache, L.

    2017-06-01

    Due to excellent mechanical properties, high entropy alloys from the system AlxCrFeCoNi can be used successfully to create composite structures containing both metallic and ceramic plates, which resists at dynamic load during high speeds impact (like projectiles, explosion). The paper presents four different composite structures made from a combination of metallic materials and ceramics plates: duralumin-ceramics, duralumin-ceramics-HEA, HEA-ceramics-HEA, HEA-ceramics-duralumin. Numerical simulation of impact behavior of the composite structures was performed by virtual methods, taking into account the mechanical properties of both materials. The best results were obtained using composite structures HEA-ceramics-HEA, HEA-ceramics-duralumin.

  20. Fracture Toughness of Advanced Ceramics at Room Temperature

    PubMed Central

    Quinn, George D.; Salem, Jonathan; Bar-on, Isa; Cho, Kyu; Foley, Michael; Fang, Ho

    1992-01-01

    This report presents the results obtained by the five U.S. participating laboratories in the Versailles Advanced Materials and Standards (VAMAS) round-robin for fracture toughness of advanced ceramics. Three test methods were used: indentation fracture, indentation strength, and single-edge pre-cracked beam. Two materials were tested: a gas-pressure sintered silicon nitride and a zirconia toughened alumina. Consistent results were obtained with the latter two test methods. Interpretation of fracture toughness in the zirconia alumina composite was complicated by R-curve and environmentally-assisted crack growth phenomena. PMID:28053447

  1. Investigations of Li-containing SiCN(O) ceramics via 7Li MAS NMR.

    PubMed

    Gumann, Sina; Nestle, Nikolaus; Liebau-Kunzmann, Verena; Riedel, Ralf

    2007-04-01

    Lithium-containing silicon (oxy)carbonitride ceramics (SiCN(O):Li) were synthesized via precursor-to-ceramic-transformation of Li-containing (poly)silazanes. The precursors were obtained by lithiation of 2,4,6-trimethyl-2,4,6-trivinylcyclotrisilazane with n-butyllithium and by reaction of a commercial poly(organosilazane) VL20 with metallic lithium. The annealing treatment was carried out at temperatures between 200 and 1400 degrees C in argon (DeltaT=200 degrees C) and yielded Li-containing silicon (oxy)carbonitride. X-ray powder diffraction revealed that the resulting SiCN(O):Li ceramics were basically amorphous up to temperatures of 1000 degrees C and formed LiSi(2)N(3), graphite and silicon carbide as crystalline phases at higher temperatures. (7)Li MAS NMR spectroscopy was carried out to investigate the structure of the Li-containing phases and to study the reaction path of metallic Li with polysilazane. Based on the NMR spectra, there is almost no difference found in the chemical shift of the SiCN(O):Li ceramics obtained at different temperatures. Accordingly, Li is assigned to be mainly coordinated to N and O present as contaminant element. Relaxation time measurements showed that the most mobile Li(+) species seems to be present in the product obtained in the pyrolysis temperature range between 600 and 1000 degrees C.

  2. Joining and Assembly of Silicon Carbide-based Advanced Ceramics and Composites for High Temperature Applications

    NASA Technical Reports Server (NTRS)

    Singh, M.

    2004-01-01

    Silicon carbide based advanced ceramics and fiber reinforced composites are under active consideration for use in wide variety of high temperature applications within the aeronautics, space transportation, energy, and nuclear industries. The engineering designs of ceramic and composite component require fabrication and manufacturing of large and complex shaped parts of various thicknesses. In many instances, it is more economical to build up complex shapes by joining simple geometrical shapes. In addition these components have to be joined or assembled with metallic sub-components. Thus, joining and attachment have been recognized as enabling technologies for successful utilization of ceramic components in various demanding applications. In this presentation, various challenges and opportunities in design, fabrication, and testing o high temperature joints in ceramic matrix composites will be presented. Silicon carbide based advanced ceramics (CVD and hot pressed), and C/SiC and SiC/SiC composites, in different shapes and sizes, have been joined using an affordable, robust ceramic joining technology (ARCJoinT). Microstructure and high temperature mechanical properties of joints in silicon carbide ceramics and CVI and melt infiltrated SiC matrix composites will,be reported. Various joint design philosophies and design issues in joining of ceramics and composites well be discussed.

  3. Advancements in all-ceramics for dental restorations and their effect on the wear of opposing dentition

    PubMed Central

    Rashid, Haroon; Sheikh, Zeeshan; Misbahuddin, Syed; Kazmi, Murtaza Raza; Qureshi, Sameer; Uddin, Muhammad Zuhaib

    2016-01-01

    Tooth wear is a process that is usually a result of tooth to tooth and/or tooth and restoration contact. The process of wear essentially becomes accelerated by the introduction of restorations inside the oral cavity, especially in case of opposing ceramic restorations. The newest materials have vastly contributed toward the interest in esthetic dental restorations and have been extensively studied in laboratories. However, despite the recent technological advancements, there has not been a valid in vivo method of evaluation involving clinical wear caused due to ceramics upon restored teeth and natural dentition. The aim of this paper is to review the latest advancements in all-ceramic materials, and their effect on the wear of opposing dentition. The descriptive review has been written after a thorough MEDLINE/PubMed search by the authors. It is imperative that clinicians are aware of recent advancements and that they should always consider the type of ceramic restorative materials used to maintain a stable occlusal relation. The ceramic restorations should be adequately finished and polished after the chair-side adjustment process of occlusal surfaces. PMID:28042280

  4. Advanced Ceramics from Preceramic Polymers Modified at the Nano-Scale: A Review.

    PubMed

    Bernardo, Enrico; Fiocco, Laura; Parcianello, Giulio; Storti, Enrico; Colombo, Paolo

    2014-03-06

    Preceramic polymers, i.e. , polymers that are converted into ceramics upon heat treatment, have been successfully used for almost 40 years to give advanced ceramics, especially belonging to the ternary SiCO and SiCN systems or to the quaternary SiBCN system. One of their main advantages is the possibility of combining the shaping and synthesis of ceramics: components can be shaped at the precursor stage by conventional plastic-forming techniques, such as spinning, blowing, injection molding, warm pressing and resin transfer molding, and then converted into ceramics by treatments typically above 800 °C. The extension of the approach to a wider range of ceramic compositions and applications, both structural and thermo-structural (refractory components, thermal barrier coatings) or functional (bioactive ceramics, luminescent materials), mainly relies on modifications of the polymers at the nano-scale, i.e. , on the introduction of nano-sized fillers and/or chemical additives, leading to nano-structured ceramic components upon thermal conversion. Fillers and additives may react with the main ceramic residue of the polymer, leading to ceramics of significant engineering interest (such as silicates and SiAlONs), or cause the formation of secondary phases, significantly affecting the functionalities of the polymer-derived matrix.

  5. Advanced Ceramics from Preceramic Polymers Modified at the Nano-Scale: A Review

    PubMed Central

    Bernardo, Enrico; Fiocco, Laura; Parcianello, Giulio; Storti, Enrico; Colombo, Paolo

    2014-01-01

    Preceramic polymers, i.e., polymers that are converted into ceramics upon heat treatment, have been successfully used for almost 40 years to give advanced ceramics, especially belonging to the ternary SiCO and SiCN systems or to the quaternary SiBCN system. One of their main advantages is the possibility of combining the shaping and synthesis of ceramics: components can be shaped at the precursor stage by conventional plastic-forming techniques, such as spinning, blowing, injection molding, warm pressing and resin transfer molding, and then converted into ceramics by treatments typically above 800 °C. The extension of the approach to a wider range of ceramic compositions and applications, both structural and thermo-structural (refractory components, thermal barrier coatings) or functional (bioactive ceramics, luminescent materials), mainly relies on modifications of the polymers at the nano-scale, i.e., on the introduction of nano-sized fillers and/or chemical additives, leading to nano-structured ceramic components upon thermal conversion. Fillers and additives may react with the main ceramic residue of the polymer, leading to ceramics of significant engineering interest (such as silicates and SiAlONs), or cause the formation of secondary phases, significantly affecting the functionalities of the polymer-derived matrix. PMID:28788548

  6. Survival of anterior cantilevered all-ceramic resin-bonded fixed dental prostheses made from zirconia ceramic.

    PubMed

    Sasse, Martin; Kern, Matthias

    2014-06-01

    This study evaluated the clinical outcome of all-ceramic resin-bonded fixed dental prostheses (RBFDPs) with a cantilevered single-retainer design made from zirconia ceramic. Forty-two anterior RBFDPs with a cantilevered single-retainer design were made from yttrium oxide-stabilized zirconium oxide ceramic. RBFDPs were inserted using Panavia 21 TC as luting agent after air-abrasion of the ceramic bonding surface. During a mean observation time of 61.8 months two debondings occurred. Both RBFDPs were rebonded using Panavia 21 TC and are still in function. A caries lesion was detected at one abutment tooth during recall and was treated with a composite filling. Therefore, the overall six-year failure-free rate according to Kaplan-Meier was 91.1%. If only debonding was defined as failure the survival rate increased to 95.2%. Since all RBFDPs are still in function the overall survival rate was 100% after six years. Cantilevered zirconia ceramic RBFDPs showed promising results within the observation period. Single-retainer resin-bonded fixed dental prostheses made from zirconia ceramic show very good mid-term clinical survival rates. They should therefore be considered as a viable treatment alternative for the replacement of single missing anterior teeth especially as compared to an implant therapy. Copyright © 2014 Elsevier Ltd. All rights reserved.

  7. Tests of NASA ceramic thermal barrier coating for gas-turbine engines

    NASA Technical Reports Server (NTRS)

    Liebert, C. H.

    1979-01-01

    A two-layer thermal barrier coating system with a bond coating of nickel-chromium-aluminum-yttrium and a ceramic coating of yttria-stabilized zirconia was tested for corrosion protection, thermal protection and durability. Full-scale gas-turbine engine tests demonstrated that this coating eliminated burning, melting, and warping of uncoated parts. During cyclic corrosion resistance tests made in marine diesel fuel products of combustion in a burner rig, the ceramic cracked on some specimens. Metallographic examination showed no base metal deterioration.

  8. Production and characterization of europium doped sol-gel yttrium oxide

    NASA Astrophysics Data System (ADS)

    Krebs, J. K.; Hobson, Christopher; Silversmith, Ann

    2004-03-01

    Sol-gel produced materials have recently gained attention for their use in producing nanoscale dielectric materials for confinement studies. Lanthanide impurities in the dielectric enable experimenters to optically probe the structure and dynamic properties of the nanoparticle hosts. We report on an alkoxide sol-gel production method used to produce trivalent europium doped yttrium oxide. Our process follows the standard hydrolysis of an alkoxide precursor with water containing the lanthanide ions. The sol is then aged and calcined at 800 ^oC to produce the powder samples. X-ray diffraction confirms the structure of the powder is that of Y_2O_3. The emission and excitation of the europium impurities is consistent with that of europium doped single crystal yttrium oxide, where it is known that the europium ions substitute for yttrium in the lattice. We therefore conclude that the sol-gel process enables the incorporation of europium ions into the yttrium oxide structure at temperatures far below the melting temperature. The results of preliminary dynamics measurements will also be discussed.

  9. Fracture toughness of advanced ceramics at room temperature

    NASA Technical Reports Server (NTRS)

    Quinn, George D.; Salem, Jonathan; Bar-On, Isa; Cho, Kyu; Foley, Michael; Fang, HO

    1992-01-01

    Results of round-robin fracture toughness tests on advanced ceramics are reported. A gas-pressure silicon nitride and a zirconia-toughened alumina were tested using three test methods: indentation fracture, indentation strength, and single-edge precracked beam. The latter two methods have produced consistent results. The interpretation of fracture toughness test results for the zirconia alumina composite is shown to be complicated by R-curve and environmentally assisted crack growth phenomena.

  10. 76 FR 11275 - In the Matter of Certain Ceramic Capacitors and Products Containing Same; Notice of Commission...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-01

    ... INTERNATIONAL TRADE COMMISSION [Investigation No. 337-TA-692] In the Matter of Certain Ceramic Capacitors and Products Containing Same; Notice of Commission Determination To Review in Part A Final Initial... importation of certain ceramic capacitors and products containing the same by reason of infringement of...

  11. Integration Science and Technology of Advanced Ceramics for Energy and Environmental Applications

    NASA Technical Reports Server (NTRS)

    Singh, M.

    2012-01-01

    The discovery of new and innovative materials has been known to culminate in major turning points in human history. The transformative impact and functional manifestation of new materials have been demonstrated in every historical era by their integration into new products, systems, assemblies, and devices. In modern times, the integration of new materials into usable products has a special relevance for the technological development and economic competitiveness of industrial societies. Advanced ceramic technologies dramatically impact the energy and environmental landscape due to potential wide scale applications in all aspects of energy production, storage, distribution, conservation, and efficiency. Examples include gas turbine propulsion systems, fuel cells, thermoelectrics, photovoltaics, distribution and transmission systems based on superconductors, nuclear power generation, and waste disposal. Robust ceramic integration technologies enable hierarchical design and manufacturing of intricate ceramic components starting with geometrically simpler units that are subsequently joined to themselves and/or to metals to create components with progressively higher levels of complexity and functionality. However, for the development of robust and reliable integrated systems with optimum performance under different operating conditions, the detailed understanding of various thermochemical and thermomechanical factors is critical. Different approaches are required for the integration of ceramic-metal and ceramic-ceramic systems across length scales (macro to nano). In this presentation, a few examples of integration of ceramic to metals and ceramic to ceramic systems will be presented. Various challenges and opportunities in design, fabrication, and testing of integrated similar (ceramic-ceramic) and dissimilar (ceramic-metal) material systems will be discussed. Potential opportunities and need for the development of innovative design philosophies, approaches, and

  12. Development of sensors for ceramic components in advanced propulsion systems

    NASA Technical Reports Server (NTRS)

    Atkinson, William H.; Cyr, M. A.; Strange, R. R.

    1994-01-01

    The 'Development of Sensors for Ceramics Components in Advanced Propulsion Systems' program was divided into two phases. The objectives of Phase 1 were to analyze, evaluate and recommend sensor concepts for the measurement of surface temperature, strain and heat flux on ceramic components for advanced propulsion systems. The results of this effort were previously published in NASA CR-182111. As a result of Phase 1, three approaches were recommended for further development: pyrometry, thin-film sensors, and thermographic phosphors. The objectives of Phase 2 were to fabricate and conduct laboratory demonstration tests of these systems. A summary report of the Phase 2 effort, together with conclusions and recommendations for each of the categories evaluated, has been submitted to NASA. Emittance tests were performed on six materials furnished by NASA Lewis Research Center. Measurements were made of various surfaces at high temperature using a Thermogage emissometer. This report describes the emittance test program and presents a summary of the results.

  13. Advanced Containment System

    DOEpatents

    Kostelnik, Kevin M.; Kawamura, Hideki; Richardson, John G.; Noda, Masaru

    2005-02-08

    An advanced containment system for containing buried waste and associated leachate. The advanced containment system comprises a plurality of casing sections with each casing section interlocked to an adjacent casing section. Each casing section includes a complementary interlocking structure that interlocks with the complementary interlocking structure on an adjacent casing section. A barrier filler substantially fills the casing sections and may substantially fill the spaces of the complementary interlocking structure to form a substantially impermeable barrier. Some of the casing sections may include sensors so that the casing sections and the zone of interest may be remotely monitored after the casing sections are emplaced in the ground.

  14. PREFACE: 3rd International Congress on Ceramics (ICC3)

    NASA Astrophysics Data System (ADS)

    Niihara, Koichi; Ohji, Tatsuki; Sakka, Yoshio

    2011-10-01

    Early in 2005, the American Ceramic Society, the European Ceramic Society and the Ceramic Society of Japan announced a collaborative effort to provide leadership for the global ceramics community that would facilitate the use of ceramic and glass materials. That effort resulted in an agreement to organize a new biennial series of the International Congress on Ceramics, convened by the International Ceramic Federation (ICF). In order to share ideas and visions of the future for ceramic and glass materials, the 1st International Congress on Ceramics (ICC1) was held in Canada, 2006, under the organization of the American Ceramic Society, and the 2nd Congress (ICC2) was held in Italy, 2008, hosted by the European Ceramic Society. Organized by the Ceramic Society of Japan, the 3rd Congress (ICC3) was held in Osaka, Japan, 14-18 November 2010. Incorporating the 23rd Fall Meeting of the Ceramic Society of Japan and the 20th Iketani Conference, ICC3 was also co-organized by the Iketani Science and Technology Foundation, and was endorsed and supported by ICF, Asia-Oceania Ceramic Federation (AOCF) as well as many other organizations. Following the style of the previous two successful Congresses, the program was designed to advance ceramic and glass technologies to the next generation through discussion of the most recent advances and future perspectives, and to engage the worldwide ceramics community in a collective effort to expand the use of these materials in both conventional as well as new and exciting applications. ICC3 consisted of 22 voluntarily organized symposia in the most topical and essential themes of ceramic and glass materials, including Characterization, design and processing technologies Electro, magnetic and optical ceramics and devices Energy and environment related ceramics and systems Bio-ceramics and bio-technologies Ceramics for advanced industry and safety society Innovation in traditional ceramics It also contained the Plenary Session and the

  15. Crack Branching and Fracture Mirror Data of Glasses and Advanced Ceramics

    NASA Technical Reports Server (NTRS)

    Choi, Sung R.; Gyekenyesi, John P.

    1998-01-01

    The fracture mirror and crack branching constants were determined from three glasses and nine advanced ceramics tested under various loading and specimen configurations in an attempt to use the constants as a data base for fractography. The ratios of fracture mirror or crack branching constant to fracture toughness were found to be approximately two for most ceramic materials tested. A demonstration of how to use the two constants as a tool for verifying stress measurements was presented for silicon nitride disk specimens subjected to high-temperature, constant stress-rate biaxial flexure testing.

  16. Ceramics for Molten Materials Containment, Transfer and Handling on the Lunar Surface

    NASA Technical Reports Server (NTRS)

    Standish, Evan; Stefanescu, Doru M.; Curreri, Peter A.

    2009-01-01

    As part of a project on Molten Materials Transfer and Handling on the Lunar Surface, molten materials containment samples of various ceramics were tested to determine their performance in contact with a melt of lunar regolith simulant. The test temperature was 1600 C with contact times ranging from 0 to 12 hours. Regolith simulant was pressed into cylinders with the approximate dimensions of 1.25 dia x 1.25cm height and then melted on ceramic substrates. The regolith-ceramic interface was examined after processing to determine the melt/ceramic interaction. It was found that the molten regolith wetted all oxide ceramics tested extremely well which resulted in chemical reaction between the materials in each case. Alumina substrates were identified which withstood contact at the operating temperature of a molten regolith electrolysis cell (1600 C) for eight hours with little interaction or deformation. This represents an improvement over alumina grades currently in use and will provide a lifetime adequate for electrolysis experiments lasting 24 hours or more. Two types of non-oxide ceramics were also tested. It was found that they interacted to a limited degree with the melt resulting in little corrosion. These ceramics, Sic and BN, were not wetted as well as the oxides by the melt, and so remain possible materials for molten regolith handling. Tests wing longer holding periods and larger volumes of regolith are necessary to determine the ultimate performance of the tested ceramics.

  17. [The application of inductively coupled plasma atomic emission spectrometry/mass spectrometry to the analysis of advanced ceramic materials].

    PubMed

    Wang, Zheng; Wang, Shi-Wei; Qiu, De-Ren; Yang, Peng-Yuan

    2009-10-01

    Advanced ceramics have been applied to various important fields such as information science, aeronautics and astronautics, and life sciences. However, the optics and electric properties of ceramics are significantly affected by the micro and trace impurities existing in the material even at very low concentration level. Thus, the accurate determination of impurities is important for materials preparation and performance. Methodology of the analysis of advanced ceramic materials using ICP-AES/MS was reviewed in the present paper for the past decade. Various techniques of sample introduction, especially advances in the authors' recent work, are described in detail. The developing trend is also presented. Sixty references are cited.

  18. Structural Ceramics Database

    National Institute of Standards and Technology Data Gateway

    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.

  19. Development and evaluation of magnesium oxide-based ceramics for chamber parts in mass-production plasma etching equipment

    NASA Astrophysics Data System (ADS)

    Kasashima, Yuji; Tsutsumi, Kota; Mitomi, Shinzo; Uesugi, Fumihiko

    2017-06-01

    In mass-production plasma etching equipment, the corrosion of ceramic chamber parts reduces the production yield of LSI and overall equipment effectiveness (OEE) owing to contamination, short useful life, and particle generation. Novel ceramics that can improve the production yield and OEE are highly required. We develop magnesium oxide (MgO)-based ceramics and evaluate them under mass-production plasma etching conditions. The results of this study indicate that the developed MgO-based ceramics with high mechanical properties and low electric resistivity have a higher resistance to corrosion in plasma etching using CF4 gas than Si and conventional ceramic materials such as aluminum oxide and yttrium oxide.

  20. Zirconia ceramics for excess weapons plutonium waste

    NASA Astrophysics Data System (ADS)

    Gong, W. L.; Lutze, W.; Ewing, R. C.

    2000-01-01

    We synthesized a zirconia (ZrO 2)-based single-phase ceramic containing simulated excess weapons plutonium waste. ZrO 2 has large solubility for other metallic oxides. More than 20 binary systems A xO y-ZrO 2 have been reported in the literature, including PuO 2, rare-earth oxides, and oxides of metals contained in weapons plutonium wastes. We show that significant amounts of gadolinium (neutron absorber) and yttrium (additional stabilizer of the cubic modification) can be dissolved in ZrO 2, together with plutonium (simulated by Ce 4+, U 4+ or Th 4+) and impurities (e.g., Ca, Mg, Fe, Si). Sol-gel and powder methods were applied to make homogeneous, single-phase zirconia solid solutions. Pu waste impurities were completely dissolved in the solid solutions. In contrast to other phases, e.g., zirconolite and pyrochlore, zirconia is extremely radiation resistant and does not undergo amorphization. Baddeleyite (ZrO 2) is suggested as the natural analogue to study long-term radiation resistance and chemical durability of zirconia-based waste forms.

  1. [Spectroscopic Research on Slag Nanocrystal Glass Ceramics Containing Rare Earth Elements].

    PubMed

    Ouyang, Shun-li; Li, Bao-wei; Zhang, Xue-feng; Jia, Xiao-lin; Zhao, Ming; Deng, Lei-bo

    2015-08-01

    The research group prepared the high-performance slag nanocrystal glass ceramics by utilizing the valuable elements of the wastes in the Chinese Bayan Obo which are characterized by their symbiotic or associated existence. In this paper, inductively coupled plasma emission spectroscopy (ICP), X-ray diffraction (XRD), Raman spectroscopy (Raman) and scanning electron microscopy (SEM) are all used in the depth analysis for the composition and structure of the samples. The experiment results of ICP, XRD and SEM showed that the principal crystalline phase of the slag nanocrystal glass ceramics containing rare earth elements is diopside, its grain size ranges from 45 to 100 nm, the elements showed in the SEM scan are basically in consistent with the component analysis of ICP. Raman analysis indicated that its amorphous phase is a three-dimensional network structure composed by the structural unit of silicon-oxy tetrahedron with different non-bridging oxygen bonds. According to the further analysis, we found that the rare earth microelement has significant effect on the network structure. Compared the nanocrystal slag glass ceramic with the glass ceramics of similar ingredients, we found that generally, the Raman band wavenumber for the former is lower than the later. The composition difference between the glass ceramics and the slag nanocrystal with the similar ingredients mainly lies on the rare earth elements and other trace elements. Therefore, we think that the rare earth elements and other trace elements remains in the slag nanocrystal glass ceramics have a significant effect on the network structure of amorphous phase. The research method of this study provides an approach for the relationship among the composition, structure and performance of the glass ceramics.

  2. The effect of yttrium and thorium on the oxidation behavior of Ni-Cr-Al alloys

    NASA Technical Reports Server (NTRS)

    Kumar, A.; Nasrallah, M.; Douglass, D. L.

    1974-01-01

    The effect of quaternary additions of 0.5% Y, 0.5 and 1.0% Th to a base alloy of Ni-10CR-5Al on the oxidation behavior and mechanism was studied during oxidation in air over the range of 1000 to 1200 C. The presence of yttrium decreased the oxidation kinetics slightly, whereas, the addition of thorium caused a slight increase. Oxide scale adherence was markedly improved by the addition of the quaternary elements. Although a number of oxides formed on yttrium containing alloys, quantitative X-ray diffraction clearly showed that the rate-controlling step was the diffusion of aluminum through short circuit paths in a thin layer of alumina that formed parabolically with time. Although the scale adherence of the yttrium containing alloy was considerably better than the base alloys, spalling did occur that was attributed to the formation of the voluminous YAG particles which grew in a mushroom-like manner, lifting the protective scale off the subrate locally. The YAG particles formed primarily at grain boundaries in the substrate in which the yttrium originally existed as YNi9.

  3. Characterization and in vitro bioactivity of zinc-containing bioactive glass and glass-ceramics.

    PubMed

    Du, Rui Lin; Chang, Jiang; Ni, Si Yu; Zhai, Wan Yin; Wang, Jun Ying

    2006-04-01

    Zinc-containing glass is prepared by the substitution of CaO in 58S bioactive glass with 0.5 and 4 wt% ZnO, and glass-ceramics are obtained by heat-treating the glass at 1,200 C. The bending strength and in vitro bioactivity of the glass and glass-ceramics are evaluated. The results indicate that Zn promotes the crystallization of SiO(2) and wollastonite in glass-ceramics, and proper crystallization can enhance the bending strength of the glass-ceramic. The in vitro results show that ZnO in glass retards the hydroxyapatite (HA) nucleation at the initial stage of simulated body fluid (SBF) soaking, but does not affect the growth of HA after long periods of soaking, and the ionic products of 58S4Z glass can stimulate the proliferation of osteoblast at certain concentrations. Osteoblasts attach well on both glass samples and glass-ceramic samples, but the high Si ion concentration released from glass samples restrains the proliferation of osteoblasts after 3 days of culture. In contrast, osteoblasts show good proliferation on glass-ceramic samples, and ZnO in glass-ceramics promotes the proliferation rate. The results in this study suggest that the glass and glass-ceramics with different ZnO content might be used as bioactive bone implant materials in different applications.

  4. Issues in nanocomposite ceramic engineering: focus on processing and properties of alumina-based composites.

    PubMed

    Palmero, Paola; Kern, Frank; Sommer, Frank; Lombardi, Mariangela; Gadow, Rainer; Montanaro, Laura

    2014-12-30

    Ceramic nanocomposites, containing at least one phase in the nanometric dimension, have received special interest in recent years. They have, in fact, demonstrated increased performance, reliability and lifetime with respect to monolithic ceramics. However, a successful approach to the production of tailored composite nanostructures requires the development of innovative concepts at each step of manufacturing, from the synthesis of composite nanopowders, to their processing and sintering.This review aims to deepen understanding of some of the critical issues associated with the manufacturing of nanocomposite ceramics, focusing on alumina-based composite systems. Two case studies are presented and briefly discussed. The former illustrates the benefits, in terms of sintered microstructure and related mechanical properties, resulting from the application of an engineering approach to a laboratory-scale protocol for the elaboration of nanocomposites in the system alumina-ZrO2-YAG (yttrium aluminium garnet). The latter illustrates the manufacturing of alumina-based composites for large-scale applications such as cutting tools, carried out by an injection molding process. The need for an engineering approach to be applied in all processing steps is demonstrated also in this second case study, where a tailored manufacturing process is required to obtain the desired results.

  5. High Temperature Tolerant Ceramic Composites Having Porous Interphases

    DOEpatents

    Kriven, Waltraud M.; Lee, Sang-Jin

    2005-05-03

    In general, this invention relates to a ceramic composite exhibiting enhanced toughness and decreased brittleness, and to a process of preparing the ceramic composite. The ceramic composite comprises a first matrix that includes a first ceramic material, preferably selected from the group including alumina (Al2O3), mullite (3Al2O3.2SiO2), yttrium aluminate garnet (YAG), yttria stabilized zirconia (YSZ), celsian (BaAl2Si2O8) and nickel aluminate (NiAl2O4). The ceramic composite also includes a porous interphase region that includes a substantially non-sinterable material. The non-sinterable material can be selected to include, for example, alumina platelets. The platelets lie in random 3-D orientation and provide a debonding mechanism, which is independent of temperature in chemically compatible matrices. The non-sinterable material induces constrained sintering of a ceramic powder resulting in permanent porosity in the interphase region. For high temperature properties, addition of a sinterable ceramic powder to the non-sinterable material provides sufficiently weak debonding interphases. The ceramic composite can be provided in a variety of forms including a laminate, a fibrous monolith, and a fiber-reinforced ceramic matrix. In the laminated systems, intimate mixing of strong versus tough microstructures were tailored by alternating various matrix-to-interphase thickness ratios to provide the bimodal laminate.

  6. Production of Zr-89 using sputtered yttrium coin targets 89Zr using sputtered yttrium coin targets.

    PubMed

    Queern, Stacy Lee; Aweda, Tolulope Aramide; Massicano, Adriana Vidal Fernandes; Clanton, Nicholas Ashby; El Sayed, Retta; Sader, Jayden Andrew; Zyuzin, Alexander; Lapi, Suzanne Elizabeth

    2017-07-01

    An increasing interest in zirconium-89 ( 89 Zr) can be attributed to the isotope's half-life which is compatible with antibody imaging using positron emission tomography (PET). The goal of this work was to develop an efficient means of production for 89 Zr that provides this isotope with high radionuclidic purity and specific activity. We investigated the irradiation of yttrium sputtered niobium coins and compared the yields and separation efficiency to solid yttrium coins. The sputtered coins were irradiated with an incident beam energy of 17.5MeV or 17.8MeV providing a degraded transmitted energy through an aluminum degrader of 12.5MeV or 12.8MeV, respectively, with various currents to determine optimal cyclotron conditions for 89 Zr production. Dissolution of the solid yttrium coin took 2h with 50mL of 2M HCl and dissolution of the sputtered coin took 15-30min with 4mL of 2M HCl. During the separation of 89 Zr from the solid yttrium coins, 77.9 ± 11.2% of the activity was eluted off in an average of 7.3mL of 1M oxalic acid whereas for the sputtered coins, 91 ± 6% was eluted off in an average of 1.2mL of 1M oxalic acid with 100% radionuclidic purity. The effective specific activity determined via DFO-SCN titration from the sputtered coins was 108±7mCi/μmol as compared to 20.3mCi/μmol for the solid yttrium coin production. ICP-MS analysis of the yttrium coin and the sputtered coins showed 99.99% yttrium removed with 178μg of yttrium in the final solution and 99.93-100% of yttrium removed with remaining range of 0-42μg of yttrium in the final solution, respectively. The specific activity calculated for the solid coin and 3 different sputtered coins using the concentration of Zr found via ICP-MS was 140±2mCi/μmol, 300±30mCi/μmol, 410±60mCi/μmol and 1719±5mCi/μmol, respectively. Labeling yields of the 89 Zr produced via sputtered targets for 89 Zr- DFO-trastuzumab were >98%. Overall, these results show the irradiation of yttrium sputtered niobium coins

  7. Transmission of Er:YAG laser through different dental ceramics.

    PubMed

    Sari, Tugrul; Tuncel, Ilkin; Usumez, Aslihan; Gutknecht, Norbert

    2014-01-01

    The aim of this study was to determine the erbium-doped yttrium aluminum garnet (Er:YAG) laser transmission ratio through different dental ceramics with different thicknesses. Laser debonding procedure of adhesively luted all-ceramic restorations is based on the transmission of laser energy through the ceramic and the ablation of resin cement, because of the transmitted laser energy. Five different dental ceramics were evaluated in this study: sintered zirconium-oxide core ceramic, monolithic zirconium-oxide ceramic, feldspathic ceramic, leucite-reinforced glass ceramic, and lithium disilicate-reinforced glass ceramic. Two ceramic discs with different thicknesses (0.5 and 1 mm) were fabricated for each group. Ceramic discs were placed between the sensor membrane of the laser power meter and the tip of the contact handpiece of an Er:YAG laser device with the aid of a custom- made acrylic holder. The transmission ratio of Er:YAG laser energy (500 mJ, 2 Hz, 1 W, 1000 μs) through different ceramic discs was measured with the power meter. Ten measurements were made for each group and the results were analyzed with two way analysis of variance (ANOVA) and Tukey honestly significant difference (HSD) tests. The highest transmission ratio was determined for lithium disilicate-reinforced ceramic with 0.5 mm thickness (88%) and the lowest was determined for feldspathic ceramic with 1 mm thickness (44%). The differences among the different ceramics and between the different thicknesses were significant (p<0.05). Ceramic type and thickness should be taken into consideration to adjust the laser irradiation parameters during laser debonding of adhesively luted all-ceramic restorations.

  8. Synthesis and characterization of cerium containing iron phosphate based glass-ceramics

    NASA Astrophysics Data System (ADS)

    Deng, Yi; Liao, Qilong; Wang, Fu; Zhu, Hanzhen

    2018-02-01

    The structure and properties of xCeO2-(100-x)(40Fe2O3-60P2O5), where x = 0, 2, 4, 6 and 8 mol%, glass-ceramics prepared by melting and slow cooling method have been investigated by using X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), differential thermal analysis (DTA) and the Product Consistency Test (PCT). The results show that the 40Fe2O3-60P2O5 sample is homogeneously amorphous and the sample containing 2 mol% CeO2 has a small amount of FePO4 phase embedded. For the sample containing up to 4 mol% CeO2, monazite CePO4 and a small amount of FePO4 appear. Spectra analysis show that the structure networks of the glass-ceramics mainly consist of orthophosphate, along with pyrophosphate and a small amount of metaphosphate units. Moreover, the leaching rates of Fe and Ce are about 3.5 × 10-5 g m-2 d-1 and 5.0 × 10-5 g m-2 d-1 respectively after immersion in deionized water at 90 °C for 56 days, indicating their good chemical durability. The conclusions imply that the prepared method may be a promising process to immobilize nuclear waste into glass-ceramic matrix.

  9. [Synthesis of strontium-containing porous hydroxyaptite ceramics and study of its biological properties].

    PubMed

    Zou, Wen; Ran, Xu; Liang, Jie; Chen, Hezhong; Luo, Jiaoming

    2012-12-01

    Strontium added into porous hydroxyaptite ceramics has the functions of improving its osseointegration, decreasing its dissolution rate and improving the bone density. Strontium-containing hydroxyaptite (Sr-HA) ceramics has been used as bone replacement and scaffold to treat the osteoporosis and bone default in clinic, but the mechanism of interfacial tissue response caused by the trace element Sr in Sr-HA ceramics still remains to be further studied. Four types of Sr-HA ceramic samples with different contents of Sr were prepared by microwave plasma sintering for testing the response of the soft tissue implanted in dog muscles in our laboratory. The contents of Sr element in the samples are 0 mol%, 1 mol%, 5 mol%, and 7 mol%, respectively. The samples were implanted in the muscle of the dogs for 4 weeks, 8 weeks and 12 weeks, respectively. The histological observations at the end of each period showed that the irritant ranking increased with the content of Sr in Sr-HA ceramics at the end of 12 weeks, and there were rich bone tissue in Sr-HA ceramic samples with 5 mol% Sr element. The overdose of element Sr is harmful to soft tissues. When the content of Sr in Sr-HA ceramic was below 5 mol%, the soft tissue response was very slight and the new bones were induced to grow well.

  10. In vivo biofilm formation on different dental ceramics.

    PubMed

    Bremer, Felicia; Grade, Sebastian; Kohorst, Philipp; Stiesch, Meike

    2011-01-01

    To investigate the formation of oral biofilm on various dental ceramics in vivo. Five different ceramic materials were included: a veneering glass- ceramic, a lithium disilicate glass-ceramic, a yttrium-stabilized zirconia (Y-TZP), a hot isostatically pressed (HIP) Y-TZP ceramic, and an HIP Y-TZP ceramic with 25% alumina. Test specimens were attached to individually designed acrylic appliances; five volunteers wore these appliances for 24 hours in the maxillary arch. After intraoral exposure, the samples were removed from the appliances and the adhering biofilms vitally stained. Then, the two-dimensional surface coating and thickness of the adhering biofilm were determined by confocal laser scanning microscopy. Statistical analysis was performed using one-way ANOVA with the level of significance set at .05. Significant differences (P < .001) in the bacterial surface coating and in the thickness of the biofilm were found between the various ceramic materials. The lowest surface coating (19.0%) and biofilm thickness (1.9 Μm) were determined on the HIP Y-TZP ceramic; the highest mean values were identified with the lithium disilicate glass-ceramic (46.8%, 12.6 Μm). Biofilm formation on various types of dental ceramics differed significantly; in particular, zirconia exhibited low plaque accumulation. In addition to its high strength, low plaque accumulation makes zirconia a promising material for various indications (including implant abutments and telescopic crowns) that previously were met only with metal-based materials.

  11. A new sol-gel process for producing Na(2)O-containing bioactive glass ceramics.

    PubMed

    Chen, Qi-Zhi; Li, Yuan; Jin, Li-Yu; Quinn, Julian M W; Komesaroff, Paul A

    2010-10-01

    The sol-gel process of producing SiO(2)-CaO bioactive glasses is well established, but problems remain with the poor mechanical properties of the amorphous form and the bioinertness of its crystalline counterpart. These properties may be improved by incorporating Na(2)O into bioactive glasses, which can result in the formation of a hard yet biodegradable crystalline phase from bioactive glasses when sintered. However, production of Na(2)O-containing bioactive glasses by sol-gel methods has proved to be difficult. This work reports a new sol-gel process for the production of Na(2)O-containing bioactive glass ceramics, potentially enabling their use as medical implantation materials. Fine powders of 45S5 (a Na(2)O-containing composition) glass ceramic have for the first time been successfully synthesized using the sol-gel technique in aqueous solution under ambient conditions, with the mean particle size being approximately 5 microm. A comparative study of sol-gel derived S70C30 (a Na(2)O-free composition) and 45S5 glass ceramic materials revealed that the latter possesses a number of features desirable in biomaterials used for bone tissue engineering, including (i) the crystalline phase Na(2)Ca(2)Si(3)O(9) that couples good mechanical strength with satisfactory biodegradability, (ii) formation of hydroxyapatite, which may promote good bone bonding and (iii) cytocompatibility. In contrast, the sol-gel derived S70C30 glass ceramic consisted of a virtually inert crystalline phase CaSiO(3). Moreover, amorphous S70C30 largely transited to CaCO(3) with minor hydroxyapatite when immersed in simulated body fluid under standard tissue culture conditions. In conclusion, sol-gel derived Na(2)O-containing glass ceramics have significant advantages over related Na(2)O-free materials, having a greatly improved combination of mechanical capability and biological absorbability. 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  12. Ceramic Coatings for Clad (The C 3 Project): Advanced Accident-Tolerant Ceramic Coatings for Zr-Alloy Cladding

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

    Sickafus, Kurt E.; Wirth, Brian; Miller, Larry

    The goal of this NEUP-IRP project is to develop a fuel concept based on an advanced ceramic coating for Zr-alloy cladding. The coated cladding must exhibit demonstrably improved performance compared to conventional Zr-alloy clad in the following respects: During normal service, the ceramic coating should decrease cladding oxidation and hydrogen pickup (the latter leads to hydriding and embrittlement). During a reactor transient (e.g., a loss of coolant accident), the ceramic coating must minimize or at least significantly delay oxidation of the Zr-alloy cladding, thus reducing the amount of hydrogen generated and the oxygen ingress into the cladding. The specific objectivesmore » of this project are as follows: To produce durable ceramic coatings on Zr-alloy clad using two possible routes: (i) MAX phase ceramic coatings or similar nitride or carbide coatings; and (ii) graded interface architecture (multilayer) ceramic coatings, using, for instance, an oxide such as yttria-stabilized zirconia (YSZ) as the outer protective layer. To characterize the structural and physical properties of the coated clad samples produced in 1. above, especially the corrosion properties under simulated normal and transient reactor operating conditions. To perform computational analyses to assess the effects of such coatings on fuel performance and reactor neutronics, and to perform fuel cycle analyses to assess the economic viability of modifying conventional Zr-alloy cladding with ceramic coatings. This project meets a number of the goals outlined in the NEUP-IRP call for proposals, including: Improve the fuel/cladding system through innovative designs (e.g. coatings/liners for zirconium-based cladding) Reduce or eliminate hydrogen generation Increase resistance to bulk steam oxidation Achievement of our goals and objectives, as defined above, will lead to safer light-water reactor (LWR) nuclear fuel assemblies, due to improved cladding properties and built-in accident resistance, as

  13. Biological Activation of Inert Ceramics: Recent Advances Using Tailored Self-Assembled Monolayers on Implant Ceramic Surfaces

    PubMed Central

    Böke, Frederik; Schickle, Karolina; Fischer, Horst

    2014-01-01

    High-strength ceramics as materials for medical implants have a long, research-intensive history. Yet, especially on applications where the ceramic components are in direct contact with the surrounding tissue, an unresolved issue is its inherent property of biological inertness. To combat this, several strategies have been investigated over the last couple of years. One promising approach investigates the technique of Self-Assembled Monolayers (SAM) and subsequent chemical functionalization to create a biologically active tissue-facing surface layer. Implementation of this would have a beneficial impact on several fields in modern implant medicine such as hip and knee arthroplasty, dental applications and related fields. This review aims to give a summarizing overview of the latest advances in this recently emerging field, along with thorough introductions of the underlying mechanism of SAMs and surface cell attachment mechanics on the cell side. PMID:28788687

  14. Advances in Ceramic Matrix Composite Blade Damping Characteristics for Aerospace Turbomachinery Applications

    NASA Technical Reports Server (NTRS)

    Min, James B.; Harris, Donald L.; Ting, J. M.

    2011-01-01

    For advanced aerospace propulsion systems, development of ceramic matrix composite integrally-bladed turbine disk technology is attractive for a number of reasons. The high strength-to-weight ratio of ceramic composites helps to reduce engine weight and the one-piece construction of a blisk will result in fewer parts count, which should translate into reduced operational costs. One shortcoming with blisk construction, however, is that blisks may be prone to high cycle fatigue due to their structural response to high vibration environments. Use of ceramic composites is expected to provide some internal damping to reduce the vibratory stresses encountered due to unsteady flow loads through the bladed turbine regions. A goal of our research was to characterize the vibration viscous damping behavior of C/SiC composites. The vibration damping properties were measured and calculated. Damping appeared to decrease with an increase in the natural frequency. While the critical damping amount of approximately 2% is required for typical aerospace turbomachinery engines, the C/SiC damping at high frequencies was less than 0.2% from our study. The advanced high-performance aerospace propulsion systems almost certainly will require even more damping than what current vehicles require. A purpose of this paper is to review some work on C/SiC vibration damping by the authors for the NASA CMC turbine blisk development program and address an importance of the further investigation of the blade vibration damping characteristics on candidate CMC materials for the NASA s advanced aerospace turbomachinery engine systems.

  15. Thermodynamic analysis of chemical stability of ceramic materials in hydrogen-containing atmospheres at high temperatures

    NASA Technical Reports Server (NTRS)

    Misra, Ajay K.

    1990-01-01

    The chemical stability of several ceramic materials in hydrogen-containing environments was analyzed with thermodynamic considerations in mind. Equilibrium calculations were made as a function of temperature, moisture content, and total system pressure. The following ceramic materials were considered in this study: SiC, Si3N4, SiO2, Al2O3, mullite, ZrO2, Y2O3, CaO, MgO, BeO, TiB2, TiC, HfC, and ZrC. On the basis of purely thermodynamic arguments, upper temperature limits are suggested for each material for long-term use in H2-containing atmospheres.

  16. Tribology of ceramics: Report of the Committee on Tribology of Ceramics

    NASA Technical Reports Server (NTRS)

    1988-01-01

    The current state of knowledge of ceramic surface structures, composition, and reactivity is reviewed. The tribological requirements of advanced mechanical systems now being deployed (in particular, heat engines) exceed the capabilities of traditional metallic-based materials because of the high temperatures encountered. Advanced ceramic materials for such applications are receiving intense scrutiny, but there is a lack of understanding of the properties and behavior of ceramic surfaces and the influence of processing on the properties of ceramics is described. The adequacy of models, ranging form atomic to macro, to describe and to predict ceramic friction and wear are discussed, as well as what is known about lubrication at elevated temperatures. From this analysis, recommendations are made for coordination, research, and development that will lead to better performance of ceramic materials in tribological systems.

  17. Advanced ceramic coating development for industrial/utility gas turbines

    NASA Technical Reports Server (NTRS)

    Vogan, J. W.; Stetson, A. R.

    1982-01-01

    A program was conducted with the objective of developing advanced thermal barrier coating (TBC) systems. Coating application was by plasma spray. Duplex, triplex and graded coatings were tested. Coating systems incorporated both NiCrAly and CoCrAly bond coats. Four ceramic overlays were tested: ZrO2.82O3; CaO.TiO2; 2CaO.SiO2; and MgO.Al2O3. The best overall results were obtained with a CaO.TiO2 coating applied to a NiCrAly bond coat. This coating was less sensitive than the ZrO2.8Y2O3 coating to process variables and part geometry. Testing with fuels contaminated with compounds containing sulfur, phosphorus and alkali metals showed the zirconia coatings were destabilized. The calcium titanate coatings were not affected by these contaminants. However, when fuels were used containing 50 ppm of vanadium and 150 ppm of magnesium, heavy deposits were formed on the test specimens and combustor components that required frequent cleaning of the test rig. During the program Mars engine first-stage turbine blades were coated and installed for an engine cyclic endurance run with the zirconia, calcium titanate, and calcium silicate coatings. Heavy spalling developed with the calcium silicate system. The zirconia and calcium titanate systems survived the full test duration. It was concluded that these two TBC's showed potential for application in gas turbines.

  18. Award-Winning CARES/Life Ceramics Durability Evaluation Software Is Making Advanced Technology Accessible

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Products made from advanced ceramics show great promise for revolutionizing aerospace and terrestrial propulsion and power generation. However, ceramic components are difficult to design because brittle materials in general have widely varying strength values. The CARES/Life software developed at the NASA Lewis Research Center eases this by providing a tool that uses probabilistic reliability analysis techniques to optimize the design and manufacture of brittle material components. CARES/Life is an integrated package that predicts the probability of a monolithic ceramic component's failure as a function of its time in service. It couples commercial finite element programs--which resolve a component's temperature and stress distribution - with reliability evaluation and fracture mechanics routines for modeling strength - limiting defects. These routines are based on calculations of the probabilistic nature of the brittle material's strength.

  19. Life prediction methodology for ceramic components of advanced heat engines. Phase 1: Volume 2, Appendices

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

    NONE

    1995-03-01

    This volume presents the following appendices: ceramic test specimen drawings and schematics, mixed-mode and biaxial stress fracture of structural ceramics for advanced vehicular heat engines (U. Utah), mode I/mode II fracture toughness and tension/torsion fracture strength of NT154 Si nitride (Brown U.), summary of strength test results and fractography, fractography photographs, derivations of statistical models, Weibull strength plots for fast fracture test specimens, and size functions.

  20. Ceramic heat exchanger

    DOEpatents

    LaHaye, Paul G.; Rahman, Faress H.; Lebeau, Thomas P. E.; Severin, Barbara K.

    1998-01-01

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

  1. Ceramic heat exchanger

    DOEpatents

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

    1998-06-16

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

  2. Recovery of yttrium from cathode ray tubes and lamps’ fluorescent powders: experimental results and economic simulation

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

    Innocenzi, V., E-mail: valentina.innocenzi1@univaq.it; De Michelis, I.; Ferella, F.

    2013-11-15

    Highlights: • Fluorescent powder of lamps. • Fluorescent powder of cathode ray rubes. • Recovery of yttrium from fluorescent powders. • Economic simulation for the processes to recover yttrium from WEEE. - Abstract: In this paper, yttrium recovery from fluorescent powder of lamps and cathode ray tubes (CRTs) is described. The process for treating these materials includes the following: (a) acid leaching, (b) purification of the leach liquors using sodium hydroxide and sodium sulfide, (c) precipitation of yttrium using oxalic acid, and (d) calcinations of oxalates for production of yttrium oxides. Experimental results have shown that process conditions necessary tomore » purify the solutions and recover yttrium strongly depend on composition of the leach liquor, in other words, whether the powder comes from treatment of CRTs or lamp. In the optimal experimental conditions, the recoveries of yttrium oxide are about 95%, 55%, and 65% for CRT, lamps, and CRT/lamp mixture (called MIX) powders, respectively. The lower yields obtained during treatments of MIX and lamp powders are probably due to the co-precipitation of yttrium together with other metals contained in the lamps powder only. Yttrium loss can be reduced to minimum changing the experimental conditions with respect to the case of the CRT process. In any case, the purity of final products from CRT, lamps, and MIX is greater than 95%. Moreover, the possibility to treat simultaneously both CRT and lamp powders is very important and interesting from an industrial point of view since it could be possible to run a single plant treating fluorescent powder coming from two different electronic wastes.« less

  3. Robust Joining and Integration Technologies for Advanced Metallic, Ceramic, and Composite Systems

    NASA Technical Reports Server (NTRS)

    Singh, M.; Shpargel, Tarah; Morscher, Gregory N.; Halbig, Michael H.; Asthana, Rajiv

    2006-01-01

    Robust integration and assembly technologies are critical for the successful implementation of advanced metallic, ceramic, carbon-carbon, and ceramic matrix composite components in a wide variety of aerospace, space exploration, and ground based systems. Typically, the operating temperature of these components varies from few hundred to few thousand Kelvin with different working times (few minutes to years). The wide ranging system performance requirements necessitate the use of different integration technologies which includes adhesive bonding, low temperature soldering, active metal brazing, diffusion bonding, ARCJoinT, and ultra high temperature joining technologies. In this presentation, a number of joining examples and test results will be provided related to the adhesive bonding and active metal brazing of titanium to C/C composites, diffusion bonding of silicon carbide to silicon carbide using titanium interlayer, titanium and hastelloy brazing to silicon carbide matrix composites, and ARCJoinT joining of SiC ceramics and SiC matrix composites. Various issues in the joining of metal-ceramic systems including thermal expansion mismatch and resulting residual stresses generated during joining will be discussed. In addition, joint design and testing issues for a wide variety of joints will be presented.

  4. Mechanical properties of concrete containing recycled concrete aggregate (RCA) and ceramic waste as coarse aggregate replacement

    NASA Astrophysics Data System (ADS)

    Khalid, Faisal Sheikh; Azmi, Nurul Bazilah; Sumandi, Khairul Azwa Syafiq Mohd; Mazenan, Puteri Natasya

    2017-10-01

    Many construction and development activities today consume large amounts of concrete. The amount of construction waste is also increasing because of the demolition process. Much of this waste can be recycled to produce new products and increase the sustainability of construction projects. As recyclable construction wastes, concrete and ceramic can replace the natural aggregate in concrete because of their hard and strong physical properties. This research used 25%, 35%, and 45% recycled concrete aggregate (RCA) and ceramic waste as coarse aggregate in producing concrete. Several tests, such as concrete cube compression and splitting tensile tests, were also performed to determine and compare the mechanical properties of the recycled concrete with those of the normal concrete that contains 100% natural aggregate. The concrete containing 35% RCA and 35% ceramic waste showed the best properties compared with the normal concrete.

  5. Ceramic automotive Stirling engine program

    NASA Technical Reports Server (NTRS)

    1986-01-01

    The Ceramic Automotive Stirling Engine Program evaluated the application of advanced ceramic materials to an automotive Stirling engine. The objective of the program was to evaluate the technical feasibility of utilizing advanced ceramics to increase peak engine operating temperature, and to evaluate the performance benefits of such an increase. Manufacturing cost estimates were also developed for various ceramic engine components and compared with conventional metallic engine component costs.

  6. Selective liquid chromatographic separation of yttrium from heavier rare earth elements using acetic acid as a novel eluent.

    PubMed

    Kifle, Dejene; Wibetoe, Grethe

    2013-09-13

    One of the major difficulties in the rare earth elements separation is purification of yttrium from heavy rare earth elements. Thus, an HPLC method using acetic acid as novel eluent was explored for selective separation of yttrium form the heavy rare earth elements. When acetic acid is used as a mobile phase yttrium eluted with the lighter lanthanides. This is contrary to its relative position amongst heavier lanthanides when eluents commonly used for separation of rare earth elements were employed. The shift in elution position of yttrium with acetic acid as eluent may reflect a relatively lower stability constant of the yttrium-AcOH complex (in the same order as for the lighter lanthanides) compared to the corresponding AcOH complexes with heavy lanthanides, enabling selective separation of yttrium from the latter. The method was successfully used for selective separation of yttrium in mixed rare earth sample containing about 80% of yttrium and about 20% of heavy rare earth oxides. Thus, the use of AcOH as eluent is an effective approach for separating and determining the trace amounts of heavy rare earth elements in large amounts of yttrium matrix. Separation was performed on C18 column by running appropriate elution programs. The effluent from the column was monitored with diode array detector at absorbance wavelength of 658nm after post column derivatization with Arsenazo III. Copyright © 2013 Elsevier B.V. All rights reserved.

  7. Absolute measurements of fast neutrons using yttrium.

    PubMed

    Roshan, M V; Springham, S V; Rawat, R S; Lee, P; Krishnan, M

    2010-08-01

    Yttrium is presented as an absolute neutron detector for pulsed neutron sources. It has high sensitivity for detecting fast neutrons. Yttrium has the property of generating a monoenergetic secondary radiation in the form of a 909 keV gamma-ray caused by inelastic neutron interaction. It was calibrated numerically using MCNPX and does not need periodic recalibration. The total yttrium efficiency for detecting 2.45 MeV neutrons was determined to be f(n) approximately 4.1x10(-4) with an uncertainty of about 0.27%. The yttrium detector was employed in the NX2 plasma focus experiments and showed the neutron yield of the order of 10(8) neutrons per discharge.

  8. Yttrium-90 microspheres for the treatment of hepatocellular carcinoma: A review

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

    Salem, Riad; Hunter, Russell D.

    2006-10-01

    To present a critical review of yttrium-90 (TheraSphere) for the treatment of hepatocellular carcinoma (HCC). Medical literature databases (Medline, Cochrane Library, and CANCERLIT) were searched for available literature concerning the treatment of HCC with TheraSphere. These publications were reviewed for scientific and clinical validity. Studies pertaining to the use of yttrium-90 for HCC date back to the 1960s. The results from the early animal safety studies established a radiation exposure range of 50-100 Gy to be used in human studies. Phase I dose escalation studies followed, which were instrumental in delineating radiation dosimetry and safety parameters in humans. These earlymore » studies emphasized the importance of differential arteriolar density between hypervascular HCC and surrounding liver parenchyma. Current trends in research have focused on advancing techniques to safely implement this technology as an alternative to traditional methods of treating unresectable HCC, such as external beam radiotherapy, conformal beam radiotherapy, ethanol ablation, trans-arterial chemoembolization, and radiofrequency ablation. Yttrium-90 (TheraSphere) is an outpatient treatment option for HCC. Current and future research should focus on implementing multicenter phase II and III trials comparing TheraSphere with other therapies for HCC.« less

  9. Using Yttra-Stabilized Zirconium Oxide Ceramics to Sense pH and Oxygen in Hydrothermal and Geothermal Applications

    NASA Astrophysics Data System (ADS)

    Manna, M. F.; Grandstaff, D. E.; Ulmer, G. C.

    2002-05-01

    Zirconium-Oxide ceramics stabilized with ~8-wt% Yttrium-Oxide can be employed to sense pH in high temperature (>90oC) aqueous environments with an accuracy of 0.05 pH log units (Lvov et al., in press), and to sense the fugacity of oxygen (fO2) in low temperature (>230oC) gaseous environments with an accuracy of 0.2 (fO2) log units. The major components, in two commercially available yttria-stabilized ceramics are yttria ( ~8-wt%) and zirconia ( ~91-wt%) with minor amounts of Ti, Fe and U. The textural differences in the two ceramics produces significantly different emf vs. 10,000/T responses. Response error can be introduced by: the ionic contribution of the softening glass, the catalytic action of the Pt sensor components, and the presence of Ti and Fe in the ceramic, which has been shown to alter the oxygen diffusivity of the ceramic. (Merino et al., 1996) The first type of ceramic contains a 3-dimensionally-continuous Ca-Al-Si feldspathic glass that acts as a sintering aid during manufacturing. The glass, which has a higher ionic conductivity than the zirconia ceramic, reduces the bulk resistivity and induces an error over the temperature ranges representing the softening point of the glass. The glass also reduces durability of the ceramic. When the glass hydrates it produces zeolites, which grow primarily in the triple-grain-junctions of the ceramic. Thus mechanically weakening the ceramic generating electronic, ionic and mechanical stability problems. The second type of ceramic contains no grain boundary glass, but does contain discrete silicate phases (such as diopside, wollastonite, periclase, silica, etc.) in the triple-grain-junctions. Because there is no inter-granular glass, the type two ceramic does have a greater bulk resistivity compared with the type one ceramic. In a gas-sensing configuration, resistivity has been shown to affect the minimum temperature of sensor operation. A sensor with a higher bulk resistivity must reach a higher minimum

  10. Thermal Conductivity of Advanced Ceramic Thermal Barrier Coatings Determined by a Steady-state Laser Heat-flux Approach

    NASA Technical Reports Server (NTRS)

    Zhu, Dong-Ming; Miller, Robert A.

    2004-01-01

    The development of low conductivity and high temperature capable thermal barrier coatings requires advanced testing techniques that can accurately and effectively evaluate coating thermal conductivity under future high-performance and low-emission engine heat-flux conditions. In this paper, a unique steady-state CO2 laser (wavelength 10.6 microns) heat-flux approach is described for determining the thermal conductivity and conductivity deduced cyclic durability of ceramic thermal and environmental barrier coating systems at very high temperatures (up to 1700 C) under large thermal gradients. The thermal conductivity behavior of advanced thermal and environmental barrier coatings for metallic and Si-based ceramic matrix composite (CMC) component applications has also been investigated using the laser conductivity approach. The relationships between the lattice and radiation conductivities as a function of heat flux and thermal gradient at high temperatures have been examined for the ceramic coating systems. The steady-state laser heat-flux conductivity approach has been demonstrated as a viable means for the development and life prediction of advanced thermal barrier coatings for future turbine engine applications.

  11. Development of Thin Film Thermocouples on Ceramic Materials for Advanced Propulsion System Applications

    NASA Technical Reports Server (NTRS)

    Holanda, R.

    1992-01-01

    Thin film thermocouples have been developed for use on metal parts in jet engines to 1000 c. However, advanced propulsion systems are being developed that will use ceramic materials and reach higher temperatures. The purpose of this work is to develop thin film thermocouples for use on ceramic materials. The new thin film thermocouples are Pt13Rh/Pt fabricated by the sputtering process. Lead wires are attached using the parallel-gap welding process. The ceramic materials tested are silicon nitride, silicon carbide, aluminum oxide, and mullite. Both steady state and thermal cycling furnace tests were performed in the temperature range to 1500 C. High-heating-rate tests were performed in an arc lamp heat-flux-calibration facility. The fabrication of the thin film thermocouples is described. The thin film thermocouple output was compared to a reference wire thermocouple. Drift of the thin film thermocouples was determined, and causes of drift are discussed. The results of high heating rate tests up to 2500 C/sec are presented. The stability of the ceramic materials is examined. It is concluded that Pt13Rh/Pt thin film thermocouples are capable of meeting lifetime goals of 50 hours or more up to temperature of 1500 C depending on the stability of the particular ceramic substrate.

  12. Development of thin film thermocouples on ceramic materials for advanced propulsion system applications

    NASA Technical Reports Server (NTRS)

    Holanda, Raymond

    1993-01-01

    Thin film thermocouples were developed for use on metal parts in jet engines to 1000 C. However, advanced propulsion systems are being developed that will use ceramic materials and reach higher temperatures. The purpose is to develop thin film thermocouples for use on ceramic materials. The new thin film thermocouples are Pt13Rh/Pt fabricated by the sputtering process. Lead wires are attached using the parallel-gap welding process. The ceramic materials tested are silicon nitride, silicon carbide, aluminum oxide, and mullite. Both steady state and thermal cycling furnace tests were performed in the temperature range to 1500 C. High-heating-rate tests were performed in an arc lamp heat-flux-calibration facility. The fabrication of the thin film thermocouples is described. The thin film thermocouple output was compared to a reference wire thermocouple. Drift of the thin film thermocouples was determined, and causes of drift are discussed. The results of high heating rate tests up to 2500 C/sec are presented. The stability of the ceramic materials is examined. It is concluded that Pt13Rh/Pt thin film thermocouples are capable of meeting lifetime goals of 50 hr or more up to temperatures of 1500 C depending on the stability of the particular ceramic substrate.

  13. Advanced Constituents and Processes for Ceramic Composite Engine Components

    NASA Technical Reports Server (NTRS)

    Yun, H. M.; DiCarlo, J. A.; Bhatt, R. T.

    2004-01-01

    The successful replacement of metal alloys by ceramic matrix composites (CMC) in hot-section engine components will depend strongly on optimizing the processes and properties of the CMC microstructural constituents so that they can synergistically provide the total CMC system with improved temperature capability and with the key properties required by the components for long-term structural service. This presentation provides the results of recent activities at NASA aimed at developing advanced silicon carbide (Sic) fiber-reinforced hybrid Sic matrix composite systems that can operate under mechanical loading and oxidizing conditions for hundreds of hours at 2400 and 2600 F, temperatures well above current metal capability. These SiC/SiC composite systems are lightweight (-30% metal density) and, in comparison to monolithic ceramics and carbon fiber-reinforced ceramic composites, are able to reliably retain their structural properties for long times under aggressive engine environments. It is shown that the improved temperature capability of the SiC/SiC systems is related first to the NASA development of the Sylramic-iBN Sic fiber, which displays high thermal stability, creep resistance, rupture resistance, and thermal conductivity, and possesses an in-situ grown BN surface layer for added environmental durability. This fiber is simply derived from Sylramic Sic fiber type that is currently produced at ATK COI Ceramics. Further capability is then derived by using chemical vapor infiltration (CVI) to form the initial portion of the hybrid Sic matrix. Because of its high creep resistance and thermal conductivity, the CVI Sic matrix is a required base constituent for all the high temperature SiC/SiC systems. By subsequently thermo- mechanical-treating the CMC preform, which consists of the S ylramic-iBN fibers and CVI Sic matrix, process-related defects in the matrix are removed, further improving matrix and CMC creep resistance and conductivity.

  14. Organosilicon Polymers as Precursors for Silicon-Containing Ceramics.

    DTIC Science & Technology

    1987-02-23

    preceramic polymer , shrinkage on pyrolysis could be considerable. Ceramic fibers of diverse chemical compositions are sought for...In the design of preceramic polymers , achievement of the desired elemental composition in the ceramic obtained from them ( SiC and Si3N4 in the...approximately one, pyrolysis of the product polymer gave a black ceramic solid in 84% yield which analysis showed to have a composition (1 SiC + 0.22

  15. Advanced Environmental Barrier Coatings Development for Si-Based Ceramics

    NASA Technical Reports Server (NTRS)

    Zhu, Dong-Ming; Choi, R. Sung; Robinson, Raymond C.; Lee, Kang N.; Bhatt, Ramakrishna T.; Miller, Robert A.

    2005-01-01

    Advanced environmental barrier coating concepts based on multi-component HfO2 (ZrO2) and modified mullite systems are developed for monolithic Si3N4 and SiC/SiC ceramic matrix composite (CMC) applications. Comprehensive testing approaches were established using the water vapor cyclic furnace, high pressure burner rig and laser heat flux steam rig to evaluate the coating water vapor stability, cyclic durability, radiation and erosion resistance under simulated engine environments. Test results demonstrated the feasibility and durability of the environmental barrier coating systems for 2700 to 3000 F monolithic Si3N4 and SiC/SiC CMC component applications. The high-temperature-capable environmental barrier coating systems are being further developed and optimized in collaboration with engine companies for advanced turbine engine applications.

  16. Yttrium recovery from primary and secondary sources: A review of main hydrometallurgical processes

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

    Innocenzi, Valentina, E-mail: valentina.innocenzi1@univaq.it; De Michelis, Ida; Kopacek, Bernd

    2014-07-15

    Highlights: • Review of the main hydrometallurgical processes to recover yttrium. • Recovery of yttrium from primary sources. • Recovery of yttrium from e-waste and other types of waste. - Abstract: Yttrium is important rare earths (REs) used in numerous fields, mainly in the phosphor powders for low-energy lighting. The uses of these elements, especially for high-tech products are increased in recent years and combined with the scarcity of the resources and the environmental impact of the technologies to extract them from ores make the recycling waste, that contain Y and other RE, a priority. The present review summarized themore » main hydrometallurgical technologies to extract Y from ores, contaminated solutions, WEEE and generic wastes. Before to discuss the works about the treatment of wastes, the processes to retrieval Y from ores are discussed, since the processes are similar and derived from those already developed for the extraction from primary sources. Particular attention was given to the recovery of Y from WEEE because the recycle of them is important not only for economical point of view, considering its value, but also for environmental impact that this could be generated if not properly disposal.« less

  17. Microhardness evaluations of CAD/CAM ceramics irradiated with CO2 or Nd:YAP laser

    PubMed Central

    Rocca, Jean Paul; Fornaini, Carlo; Medioni, Etienne; Brulat-Bouchard, Nathalie

    2017-01-01

    Background and aims The aim of this study was to measure the microhardness values of irradiated computer-aided design/computer-aided manufacturing (CAD/CAM) ceramics surfaces before and after thermal treatment. Materials and Methods Sixty CAD/CAM ceramic discs were prepared and grouped by material, i.e. lithium disilicate ceramic (Emax CAD) and zirconia ceramic (Emax ZirCAD). Laser irradiation at the material surface was performed with a carbon dioxide laser at 5 Watt (W) or 10 W power in continuous mode (CW mode), or with a neodymium:yttrium aluminum perovskite (Nd:YAP) laser at 10 W on graphite and non-graphite surfaces. Vickers hardness was tested at 0.3 kgf for lithium disilicate and 1 kgf for zirconia. Results Emax CAD irradiated with CO2 at 5 W increased microhardness by 6.32 GPa whereas Emax ZirCAD irradiated with Nd:YAP decreased microhardness by 17.46 GPa. Conclusion CO2 laser effectively increases the microhardness of lithium disilicate ceramics (Emax CAD). PMID:28740324

  18. Ceramics for engines

    NASA Technical Reports Server (NTRS)

    Kiser, James D.; Levine, Stanley R.; Dicarlo, James A.

    1987-01-01

    Structural ceramics were under nearly continuous development for various heat engine applications since the early 1970s. These efforts were sustained by the properties that ceramics offer in the areas of high-temperature strength, environmental resistance, and low density and the large benefits in system efficiency and performance that can result. The promise of ceramics was not realized because their brittle nature results in high sensitivity to microscopic flaws and catastrophic fracture behavior. This translated into low reliability for ceramic components and thus limited their application in engines. For structural ceramics to successfully make inroads into the terrestrial heat engine market requires further advances in low cost, net shape fabrication of high reliability components, and improvements in properties such as toughness, and strength. These advances will lead to very limited use of ceramics in noncritical applications in aerospace engines. For critical aerospace applications, an additional requirement is that the components display markedly improved toughness and noncatastrophic or graceful fracture. Thus the major emphasis is on fiber-reinforced ceramics.

  19. ASTM Committee C28: International Standards for Properties and Performance of Advanced Ceramics, Three Decades of High-quality, Technically-rigorous Normalization

    NASA Technical Reports Server (NTRS)

    Jenkins, Michael G.; Salem, Jonathan A.

    2016-01-01

    Physical and mechanical properties and performance of advanced ceramics and glasses are difficult to measure correctly without the proper techniques. For over three decades, ASTM Committee C28 on Advanced Ceramics, has developed high quality, rigorous, full-consensus standards (e.g., test methods, practices, guides, terminology) to measure properties and performance of monolithic and composite ceramics that may be applied to glasses in some cases. These standards testing particulars for many mechanical, physical, thermal, properties and performance of these materials. As a result these standards provide accurate, reliable, repeatable and complete data. Within Committee C28 users, producers, researchers, designers, academicians, etc. have written, continually updated, and validated through round-robin test programs, nearly 50 standards since the Committees founding in 1986. This paper provides a retrospective review of the 30 years of ASTM Committee C28 including a graphical pictogram listing of C28 standards along with examples of the tangible benefits of advanced ceramics standards to demonstrate their practical applications.

  20. Test model designs for advanced refractory ceramic materials

    NASA Technical Reports Server (NTRS)

    Tran, Huy Kim

    1993-01-01

    The next generation of space vehicles will be subjected to severe aerothermal loads and will require an improved thermal protection system (TPS) and other advanced vehicle components. In order to ensure the satisfactory performance system (TPS) and other advanced vehicle materials and components, testing is to be performed in environments similar to space flight. The design and fabrication of the test models should be fairly simple but still accomplish test objectives. In the Advanced Refractory Ceramic Materials test series, the models and model holders will need to withstand the required heat fluxes of 340 to 817 W/sq cm or surface temperatures in the range of 2700 K to 3000 K. The model holders should provide one dimensional (1-D) heat transfer to the samples and the appropriate flow field without compromising the primary test objectives. The optical properties such as the effective emissivity, catalytic efficiency coefficients, thermal properties, and mass loss measurements are also taken into consideration in the design process. Therefore, it is the intent of this paper to demonstrate the design schemes for different models and model holders that would accommodate these test requirements and ensure the safe operation in a typical arc jet facility.

  1. Hydrothermal synthesis, crystal structures and photoluminescence properties of mixed europium-yttrium organic frameworks

    NASA Astrophysics Data System (ADS)

    Han, Yinfeng; Fu, Lianshe; Mafra, Luís; Shi, Fa-Nian

    2012-02-01

    Three mixed europium-yttrium organic frameworks: Eu2-xYx(Mel)(H2O)6 (Mel=mellitic acid or benzene-1,2,3,4,5,6-hexacarboxylic acid, x=0.38 1, 0.74 2, and 0.86 3) have been synthesized and characterized. All the compounds contain a 3-D net with (4, 8)-flu topology. The study indicates that the photoluminescence properties are effectively affected by the different ratios of europium and yttrium ions, the quantum efficiency is increased and the Eu3+ lifetime becomes longer in these MOFs than those of the Eu analog.

  2. High-Temperature Wettability and Interactions between Y-Containing Ni-Based Alloys and Various Oxide Ceramics.

    PubMed

    Li, Jinpeng; Zhang, Huarui; Gao, Ming; Li, Qingling; Bian, Weidong; Tao, Tongxiang; Zhang, Hu

    2018-05-07

    To obtain appropriate crucible materials for vacuum induction melting of MCrAlY alloys, four different oxide ceramics, including MgO, Y₂O₃, Al₂O₃, and ZrO₂, with various microstructures were designed and characterized. The high-temperature wettability and interactions between Ni-20Co-20Cr-10Al-1.5Y alloys and oxide ceramics were studied by sessile drop experiments under vacuum. The results showed that all the systems exhibited non-wetting behavior. The contact angles were stable during the melting process of alloys and the equilibrium contact angles were 140° (MgO), 148° (Y₂O₃), 154° (Al₂O₃), and 157° (ZrO₂), respectively. The interfacial reaction between the ceramic substrates and alloys occurred at high temperature. Though the ceramics had different microstructures, similar continuous Y₂O₃ reaction layer with thicknesses of about 25 μm at the alloy-ceramic interface in MgO, Al₂O₃, and ZrO₂ systems formed. The average area percentage of oxides in the alloy matrices were 0.59% (MgO), 0.11% (Al₂O₃), 0.09% (ZrO₂), and 0.02% (Y₂O₃), respectively. The alloys, after reacting with MgO ceramic, had the highest inclusion content, while those with the lowest content were in the Y₂O₃ system. Y₂O₃ ceramic was the most beneficial for vacuum induction melting of high-purity Y-containing Ni-based alloys.

  3. Structural ceramics

    NASA Technical Reports Server (NTRS)

    Craig, Douglas F.

    1992-01-01

    This presentation gives a brief history of the field of materials sciences and goes on to expound the advantages of the fastest growing area in that field, namely ceramics. Since ceramics are moving to fill the demand for lighter, stronger, more corrosion resistant materials, advancements will rely more on processing and modeling from the atomic scale up which is made possible by advanced analytical, computer, and processing techniques. All information is presented in viewgraph format.

  4. Ceramics potential in automotive powerplants

    NASA Technical Reports Server (NTRS)

    Mclean, A. F.

    1983-01-01

    The paper addresses the potential that ceramic materials can play an important role in future automotive powerplants - both advanced heat engines and advanced battery systems. A number of related experimental programs are reviewed including ceramics for gasoline and diesel piston engines, gas turbine and Stirling Engines and sodium-sulfur batteries. A strong integrated program to develop ceramics technology is recommended.

  5. Advanced Material-Ordered Nanotubular Ceramic Membranes Covalently Capped with Single-Wall Carbon Nanotubes.

    PubMed

    Al-Gharabli, Samer; Hamad, Eyad; Saket, Munib; Abu El-Rub, Ziad; Arafat, Hassan; Kujawski, Wojciech; Kujawa, Joanna

    2018-05-07

    Advanced ceramic materials with a well-defined nano-architecture of their surfaces were formed by applying a two-step procedure. Firstly, a primary amine was docked on the ordered nanotubular ceramic surface via a silanization process. Subsequently, single-wall carbon nanotubes (SWCNTs) were covalently grafted onto the surface via an amide building block. Physicochemical (e.g., hydrophobicity, and surface free energy (SFE)), mechanical, and tribological properties of the developed membranes were improved significantly. The design, preparation, and extended characterization of the developed membranes are presented. Tools such as high-resolution transmission electron microscopy (HR-TEM), single-area electron diffraction (SAED) analysis, microscopy, tribology, nano-indentation, and Raman spectroscopy, among other techniques, were utilized in the characterization of the developed membranes. As an effect of hydrophobization, the contact angles (CAs) changed from 38° to 110° and from 51° to 95° for the silanization of ceramic membranes 20 (CM20) and CM100, respectively. SWCNT functionalization reduced the CAs to 72° and 66° for ceramic membranes carbon nanotubes 20 (CM-CNT-20) and CM-CNT-100, respectively. The mechanical properties of the developed membranes improved significantly. From the nanotribological study, Young’s modulus increased from 3 to 39 GPa for CM-CNT-20 and from 43 to 48 GPa for pristine CM-CNT-100. Furthermore, the nanohardness increased by about 80% after the attachment of CNTs for both types of ceramics. The proposed protocol within this work for the development of functionalized ceramic membranes is both simple and efficient.

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

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

    Amoroso, J. W.; Marra, J. C.

    2015-08-26

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

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

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

    Amoroso, J. W.; Marra, J. C.

    2015-08-26

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

  8. Easy Debonding of Ceramic Brackets Bonded with a Light-Cured Orthodontic Adhesive Containing Microcapsules with a CO2 Laser.

    PubMed

    Arima, Shiori; Namura, Yasuhiro; Tamura, Takahiko; Shimizu, Noriyoshi

    2018-03-01

    An easy debonding method for ceramic brackets using a light-cured Bis-GMA resin containing heat-expandable microcapsules and CO 2 laser was investigated. Ceramic brackets are used frequently in orthodontic treatment because of their desirable esthetic properties. However, the application of heavy force to ceramic brackets in debonding can fracture the tooth enamel and ceramic brackets, causing tooth pain. In total, 60 freshly extracted bovine permanent mandibular incisors were divided randomly into 10 groups of 6 specimens each, corresponding to the number of variables tested. Ceramic brackets were bonded to bovine permanent mandibular incisors using an orthodontic bonding agent containing heat-expandable microcapsules at different levels (0-30 wt%) and resin composite paste, and cured by a curing device. The bond strengths were measured before and after CO 2 laser irradiation, and the temperature increase in the pulp chamber in fresh human first premolars was also evaluated. With CO 2 laser irradiation for 5 sec to the bracket, the bond strength in the 25% microcapsule group decreased significantly, to ∼0.17-fold, compared with that of the no-laser group (p < 0.05). The maximum temperature increase in the pulp chamber was 5.3°C with laser irradiation, which was less than the level that induces pulp damage. From these results, it seems likely that the combined use of a light-cured orthodontic bonding agent containing microcapsules and a CO 2 laser is a simple debonding system for ceramic brackets, with less debonding time and enamel damage.

  9. Hydrothermal synthesis, crystal structures and photoluminescence properties of mixed europium-yttrium organic frameworks

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

    Han Yinfeng; Department of Chemistry and Environmental Science, Taishan University, Taian 271021; Fu Lianshe

    Three mixed europium-yttrium organic frameworks: Eu{sub 2-x}Y{sub x}(Mel)(H{sub 2}O){sub 6} (Mel=mellitic acid or benzene-1,2,3,4,5,6-hexacarboxylic acid, x=0.38 1, 0.74 2, and 0.86 3) have been synthesized and characterized. All the compounds contain a 3-D net with (4, 8)-flu topology. The study indicates that the photoluminescence properties are effectively affected by the different ratios of europium and yttrium ions, the quantum efficiency is increased and the Eu{sup 3+} lifetime becomes longer in these MOFs than those of the Eu analog. - Graphical abstract: Three mixed europium and yttrium organic frameworks: Eu{sub 2-x}Y{sub x}(Mel)(H{sub 2}O){sub 6} (Mel=mellitic acid) have been synthesized and characterized.more » All the compounds contain a 3-D net with (4, 8)-flu topology. The study indicates that the photoluminescence properties are effectively affected by the different ratios of europium and yttrium ions, the quantum efficiency is increased and the Eu{sup 3+} lifetime becomes longer in these MOFs than those of the Eu analog. Highlights: Black-Right-Pointing-Pointer Three (4, 8)-flu topological mixed Eu and Y MOFs were synthesized under mild conditions. Black-Right-Pointing-Pointer Metal ratios were refined by the single crystal data consistent with the EDS analysis. Black-Right-Pointing-Pointer Mixed Eu and Y MOFs show longer lifetime and higher quantum efficiency than the Eu analog. Black-Right-Pointing-Pointer Adding inert lanthanide into luminescent MOFs enlarges the field of luminescent MOFs.« less

  10. Ceramic membranes for catalytic membrane reactors with high ionic conductivities and low expansion properties

    DOEpatents

    Mackay, Richard; Sammells, Anthony F.

    2000-01-01

    Ceramics of the composition: Ln.sub.x Sr.sub.2-x-y Ca.sub.y B.sub.z M.sub.2-z O.sub.5+.delta. where Ln is an element selected from the fblock lanthanide elements and yttrium or mixtures thereof; B is an element selected from Al, Ga, In or mixtures thereof; M is a d-block transition element of mixtures thereof; 0.01.ltoreq.x.ltoreq.1.0; 0.01.ltoreq.y.ltoreq.0.7; 0.01.ltoreq.z.ltoreq.1.0 and .delta. is a number that varies to maintain charge neutrality are provided. These ceramics are useful in ceramic membranes and exhibit high ionic conductivity, high chemical stability under catalytic membrane reactor conditions and low coefficients of expansion. The materials of the invention are particularly useful in producing synthesis gas.

  11. Study of the Wavelength Dependence in Laser Ablation of Advanced Ceramics and Glass-Ceramic Materials in the Nanosecond Range

    PubMed Central

    Sola, Daniel; Peña, Jose I.

    2013-01-01

    In this work, geometrical dimensions and ablation yields as a function of the machining method and reference position were studied when advanced ceramics and glass-ceramic materials were machined with pulsed lasers in the nanosecond range. Two laser systems, emitting at 1064 and 532 nm, were used. It was shown that the features obtained depend on whether the substrate is processed by means of pulse bursts or by grooves. In particular, when the samples were processed by grooves, machined depth, removed volume and ablation yields reached their maximum, placing the sample out of focus. It was shown that these characteristics do not depend on the processing conditions, the wavelength or the optical configuration, and that this is intrinsic behavior of the processing method. Furthermore, the existence of a close relation between material hardness and ablation yields was demonstrated. PMID:28788391

  12. Method of sintering ceramic materials

    DOEpatents

    Holcombe, Cressie E.; Dykes, Norman L.

    1992-01-01

    A method for sintering ceramic materials is described. A ceramic article is coated with layers of protective coatings such as boron nitride, graphite foil, and niobium. The coated ceramic article is embedded in a container containing refractory metal oxide granules and placed within a microwave oven. The ceramic article is heated by microwave energy to a temperature sufficient to sinter the ceramic article to form a densified ceramic article having a density equal to or greater than 90% of theoretical density.

  13. Method of sintering ceramic materials

    DOEpatents

    Holcombe, C.E.; Dykes, N.L.

    1992-11-17

    A method for sintering ceramic materials is described. A ceramic article is coated with layers of protective coatings such as boron nitride, graphite foil, and niobium. The coated ceramic article is embedded in a container containing refractory metal oxide granules and placed within a microwave oven. The ceramic article is heated by microwave energy to a temperature sufficient to sinter the ceramic article to form a densified ceramic article having a density equal to or greater than 90% of theoretical density. 2 figs.

  14. Sodium nitrate containing mixture for producing ceramic-glass-ceramic seal by microwave heating

    DOEpatents

    Blake, R.D.; Meek, T.T.

    1984-10-10

    A mixture for, and method of using such a mixture, for producing a ceramic-glass-ceramic seal by the use of microwave energy are disclosed, wherein the mixture comprises a glass sealing material, a coupling agent, and an oxidizer. The seal produced exhibits greater strength due to its different microstructure. Sodium nitrate is the most preferred oxidizer.

  15. Efficient lasing in Yb:(YLa){sub 2}O{sub 3} ceramics

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

    Snetkov, I L; Mukhin, I B; Palashov, O V

    2015-02-28

    A high-optical-quality sample of Yb{sub 0.1}Y{sub 1.7}La{sub 0.2}O{sub 3} ceramics is prepared using a recently developed technique of selfpropagating high-temperature synthesis of rare-earth-doped yttrium oxide nanopowder from acetate – nitrates of metals. Its optical and spectral characteristics are studied, and quasi-cw lasing at a wavelength of 1033 nm is achieved with a power of 7 W and a slope efficiency of 25%. (lasers)

  16. High energy resolution with transparent ceramic garnet scintillators

    NASA Astrophysics Data System (ADS)

    Cherepy, N. J.; Seeley, Z. M.; Payne, S. A.; Beck, P. R.; Swanberg, E. L.; Hunter, S.; Ahle, L.; Fisher, S. E.; Melcher, C.; Wei, H.; Stefanik, T.; Chung, Y.-S.; Kindem, J.

    2014-09-01

    Breakthrough energy resolution, R(662keV) < 4%, has been achieved with an oxide scintillator, Cerium-doped Gadolinium Yttrium Gallium Aluminum Garnet, or GYGAG(Ce). Transparent ceramic GYGAG(Ce), has a peak emission wavelength of 550 nm that is better matched to Silicon photodetectors than to standard PMTs. We are therefore developing a spectrometer based on pixelated GYGAG(Ce) on a Silicon photodiode array that can provide R(662 keV) = 3.6%. In comparison, with large 1-2 in3 size GYGAG(Ce) ceramics we obtain R(662 keV) = 4.6% with PMT readout. We find that ceramic GYGAG(Ce) of a given stoichiometric chemical composition can exhibit very different scintillation properties, depending on sintering conditions and post-anneal treatments. Among the characteristics of transparent ceramic garnet scintillators that can be controlled by fabrication conditions are: scintillation decay components and their amplitudes, intensity and duration of afterglow, thermoluminescence glow curve peak positions and amplitudes, integrated light yield, light yield non-proportionality - as measured in the Scintillator Light Yield Non-Proportionality Characterization Instrument (SLYNCI), and energy resolution for gamma spectroscopy. Garnet samples exhibiting a significant fraction of Cerium dopant in the tetravalent valence also exhibit: faster overall scintillation decay, very low afterglow, high light yield, but poor light yield proportionality and degraded energy resolution.

  17. Effects of Laser Treatment on the Bond Strength of Differently Sintered Zirconia Ceramics.

    PubMed

    Dede, Doğu Ömür; Yenisey, Murat; Rona, Nergiz; Öngöz Dede, Figen

    2016-07-01

    The purpose of this study was to investigate the effects of carbon dioxide (CO2) and Erbium-doped yttrium aluminum garnet (Er:YAG) laser irradiations on the shear bond strength (SBS) of differently sintered zirconia ceramics to resin cement. Eighty zirconia specimens were prepared, sintered in two different periods (short = Ss, long = Ls), and divided into four treatment groups (n = 10 each). These groups were (a) untreated (control), (b) Er:YAG laser irradiated with 6 W power for 5 sec, (c) CO2 laser with 2 W power for 10 sec, (d) CO2 laser with 4 W power for 10 sec. Scanning electron microscope (SEM) images were recorded for each of the eight groups. Eighty composite resin discs (3 × 3 mm) were fabricated and cemented with an adhesive resin cement to ceramic specimens. The SBS test was performed after specimens were stored in water for 24 h by an universal testing machine at a crosshead speed of 1 mm/min. Data were statistically analyzed with two way analysis of variance (ANOVA) and Tukey honest significant difference (HSD) test (α = 0.05). According to the ANOVA, the sintering time, surface treatments and their interaction were statistically significant (p < 0.05). Although each of the laser-irradiated groups were significantly higher than the control groups, there was no statistically significant difference among them (p > 0.05). Variation in sintering time from 2.5 to 5.0 h may have influenced the SBS of Yttrium-stabilized tetragonal zirconia polycrystalline (Y-TZP) ceramics. Although CO2 and Er:YAG laser irradiation techniques may increase the SBS values of both tested zirconia ceramics, they are recommended for clinicians as an alternative pretreatment method.

  18. High-Temperature Wettability and Interactions between Y-Containing Ni-Based Alloys and Various Oxide Ceramics

    PubMed Central

    Li, Jinpeng; Gao, Ming; Li, Qingling; Bian, Weidong; Tao, Tongxiang; Zhang, Hu

    2018-01-01

    To obtain appropriate crucible materials for vacuum induction melting of MCrAlY alloys, four different oxide ceramics, including MgO, Y2O3, Al2O3, and ZrO2, with various microstructures were designed and characterized. The high-temperature wettability and interactions between Ni-20Co-20Cr-10Al-1.5Y alloys and oxide ceramics were studied by sessile drop experiments under vacuum. The results showed that all the systems exhibited non-wetting behavior. The contact angles were stable during the melting process of alloys and the equilibrium contact angles were 140° (MgO), 148° (Y2O3), 154° (Al2O3), and 157° (ZrO2), respectively. The interfacial reaction between the ceramic substrates and alloys occurred at high temperature. Though the ceramics had different microstructures, similar continuous Y2O3 reaction layer with thicknesses of about 25 μm at the alloy-ceramic interface in MgO, Al2O3, and ZrO2 systems formed. The average area percentage of oxides in the alloy matrices were 0.59% (MgO), 0.11% (Al2O3), 0.09% (ZrO2), and 0.02% (Y2O3), respectively. The alloys, after reacting with MgO ceramic, had the highest inclusion content, while those with the lowest content were in the Y2O3 system. Y2O3 ceramic was the most beneficial for vacuum induction melting of high-purity Y-containing Ni-based alloys. PMID:29735958

  19. Biokinetics of yttrium and comparison with its geochemical twin holmium

    DOE PAGES

    Leggett, Rich

    2017-06-01

    The transition metal yttrium (Y, atomic number 39) is chemically similar to elements in the lanthanide family (atomic numbers 57-71, lanthanum through lutetium) and is always present with the lanthanides in rare earth ores. Yttrium and the lanthanide holmium are particularly close chemical and physical analogues and are referred to as geochemical twins because they typically show little fractionation in geological material. Extensive measurements on rocks, soils, and meteorites indicate that the Y/Ho mass concentration ratio rarely falls far from the “chondritic” or “solar system” ratio of ~26. Our paper presents a new biokinetic model for yttrium in adult humansmore » and examines whether yttrium and holmium may be biological as well as geochemical twins. Collected data on yttrium and holmium in plants and human tissues do not allow precise derivations of Y/Ho concentration ratios but with occasional exceptions yield ratios that are reasonably consistent with chondritic values. Predictions of the time-dependent behavior of yttrium in adult humans based on the yttrium model presented here closely approximate predictions of the behavior of holmium based on a previously developed model for holmium. We know that yttrium and holmium are close biological analogues, but the available comparative data are too limited and imprecise to reveal whether there are any significant differences in their biological behavior.« less

  20. FY2016 Ceramic Fuels Development Annual Highlights

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

    Mcclellan, Kenneth James

    Key challenges for the Advanced Fuels Campaign are the development of fuel technologies to enable major increases in fuel performance (safety, reliability, power and burnup) beyond current technologies, and development of characterization methods and predictive fuel performance models to enable more efficient development and licensing of advanced fuels. Ceramic fuel development activities for fiscal year 2016 fell within the areas of 1) National and International Technical Integration, 2) Advanced Accident Tolerant Ceramic Fuel Development, 3) Advanced Techniques and Reference Materials Development, and 4) Fabrication of Enriched Ceramic Fuels. High uranium density fuels were the focus of the ceramic fuels efforts.more » Accomplishments for FY16 primarily reflect the prioritization of identification and assessment of new ceramic fuels for light water reactors which have enhanced accident tolerance while also maintaining or improving normal operation performance, and exploration of advanced post irradiation examination techniques which will support more efficient testing and qualification of new fuel systems.« less

  1. Prototype Development of Remote Operated Hot Uniaxial Press (ROHUP) to Fabricate Advanced Tc-99 Bearing Ceramic Waste Forms - 13381

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

    Alaniz, Ariana J.; Delgado, Luc R.; Werbick, Brett M.

    The objective of this senior student project is to design and build a prototype construction of a machine that simultaneously provides the proper pressure and temperature parameters to sinter ceramic powders in-situ to create pellets of rather high densities of above 90% (theoretical). This ROHUP (Remote Operated Hot Uniaxial Press) device is designed specifically to fabricate advanced ceramic Tc-99 bearing waste forms and therefore radiological barriers have been included in the system. The HUP features electronic control and feedback systems to set and monitor pressure, load, and temperature parameters. This device operates wirelessly via portable computer using Bluetooth{sup R} technology.more » The HUP device is designed to fit in a standard atmosphere controlled glove box to further allow sintering under inert conditions (e.g. under Ar, He, N{sub 2}). This will further allow utilizing this HUP for other potential applications, including radioactive samples, novel ceramic waste forms, advanced oxide fuels, air-sensitive samples, metallic systems, advanced powder metallurgy, diffusion experiments and more. (authors)« less

  2. Rare earths, the lanthanides, yttrium and scandium

    USGS Publications Warehouse

    Hedrick, J.B.

    2006-01-01

    In 2005, rare earths were not mined in the United States. The major supplier, Molycorp, continued to maintain a large stockpile of rare-earth concentrates and compounds. Consumption decreased of refined rare-earth products. The United States remained a major importer and exporter of rare earths in 2005. During the same period, yttrium was not mined or refined in the US. Hence, supply of yttrium compounds for refined yttrium products came from China, France and Japan. Scandium was not also mined. World production was primarily in China, Russia and Ukraine. Demand for rare earths in 2006 is expected to be closely tied to economic conditions in the US.

  3. Industry tests of NASA ceramic thermal barrier coating. [for gas turbine engine applications

    NASA Technical Reports Server (NTRS)

    Liebert, C. H.; Stepka, F. S.

    1979-01-01

    Ceramic thermal barrier coating (TBC) system was tested by industrial and governmental organizations for a variety of aeronautical, marine, and ground-based gas turbine engine applications. This TBC is a two-layer system with a bond coating of nickel-chromium-aluminum-yttrium (Ni-16Cr-6Al-0.6Y, in wt. percent) and a ceramic coating of yttria-stabilized zirconia (ZrO2-12Y2O3, in wt. percent). Seven tests evaluated the system's thermal protection and durability. Five other tests determined thermal conductivity, vibratory fatigue characteristics, and corrosion resistance of the system. The information presented includes test results and photographs of the coated parts. Recommendations are made for improving the coating procedures.

  4. Polythermal investigation of viscosity of solution of metal carboxylates in VIK-grade mixed carboxylic acids: Yttrium and gadolinium carboxylates

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

    Mezhov, E.A.; Samatov, A.V.; Troyanovskii, L.V.

    Kinematic viscosities have been measured for solutions of yttrium and gadolinium carboxylates in grade VIK mixed carboxylic acids (MCA). It has been established that the optimal fluidity of these metal carboxylate solutions for application to articles is reached at 333 K. A regression model has been developed to describe the concentration and temperature dependences of the viscosity of yttrium- and gadolinium-containing MCA solutions. 2 refs., 3 tabs.

  5. Surface-Directed Synthesis of Erbium-Doped Yttrium Oxide Nanoparticles within Organosilane Zeptoliter Containers

    PubMed Central

    2015-01-01

    We introduce an approach to synthesize rare earth oxide nanoparticles using high temperature without aggregation of the nanoparticles. The dispersity of the nanoparticles is controlled at the nanoscale by using small organosilane molds as reaction containers. Zeptoliter reaction vessels prepared from organosilane self-assembled monolayers (SAMs) were used for the surface-directed synthesis of rare earth oxide (REO) nanoparticles. Nanopores of octadecyltrichlorosilane were prepared on Si(111) using particle lithography with immersion steps. The nanopores were filled with a precursor solution of erbium and yttrium salts to confine the crystallization step to occur within individual zeptoliter-sized organosilane reaction vessels. Areas between the nanopores were separated by a matrix film of octadecyltrichlorosilane. With heating, the organosilane template was removed by calcination to generate a surface array of erbium-doped yttria nanoparticles. Nanoparticles synthesized by the surface-directed approach retain the periodic arrangement of the nanopores formed from mesoparticle masks. While bulk rare earth oxides can be readily prepared by solid state methods at high temperature (>900 °C), approaches for preparing REO nanoparticles are limited. Conventional wet chemistry methods are limited to low temperatures according to the boiling points of the solvents used for synthesis. To achieve crystallinity of REO nanoparticles requires steps for high-temperature processing of samples, which can cause self-aggregation and dispersity in sample diameters. The facile steps for particle lithography address the problems of aggregation and the requirement for high-temperature synthesis. PMID:25163977

  6. Development of Sensors for Ceramic Components in Advanced Propulsion Systems. Phase 2; Temperature Sensor Systems Evaluation

    NASA Technical Reports Server (NTRS)

    Atkinson, W. H.; Cyr, M. A.; Strange, R. R.

    1994-01-01

    The 'development of sensors for ceramic components in advanced propulsion systems' program is divided into two phases. The objectives of Phase 1 were to analyze, evaluate and recommend sensor concepts for the measurement of surface temperature, strain and heat flux on ceramic components for advanced propulsion systems. The results of this effort were previously published in NASA CR-182111. As a result of Phase 1, three approaches were recommended for further development: pyrometry, thin-film sensors, and thermographic phosphors. The objective of Phase 2 were to fabricate and conduct laboratory demonstration tests of these systems. Six materials, mutually agreed upon by NASA and Pratt & Whitney, were investigated under this program. This report summarizes the Phase 2 effort and provides conclusions and recommendations for each of the categories evaluated.

  7. Making Ceramic Components For Advanced Aircraft Engines

    NASA Technical Reports Server (NTRS)

    Franklin, J. E.; Ezis, A.

    1994-01-01

    Lightweight, oxidation-resistant silicon nitride components containing intricate internal cooling and hydraulic passages and capable of withstanding high operating temperatures made by ceramic-platelet technology. Used to fabricate silicon nitride test articles of two types: components of methane-cooled regenerator for air turbo ramjet engine and components of bipropellant injector for rocket engine. Procedures for development of more complex and intricate components established. Technology has commercial utility in automotive, aircraft, and environmental industries for manufacture of high-temperature components for use in regeneration of fuels, treatment of emissions, high-temperature combustion devices, and application in which other high-temperature and/or lightweight components needed. Potential use in fabrication of combustors and high-temperature acoustic panels for suppression of noise in future high-speed aircraft.

  8. Ceramic Parts for Turbines

    NASA Technical Reports Server (NTRS)

    Jones, R. D.; Carpenter, Harry W.; Tellier, Jim; Rollins, Clark; Stormo, Jerry

    1987-01-01

    Abilities of ceramics to serve as turbine blades, stator vanes, and other elements in hot-gas flow of rocket engines discussed in report. Ceramics prime candidates, because of resistance to heat, low density, and tolerance of hostile environments. Ceramics considered in report are silicon nitride, silicon carbide, and new generation of such ceramic composites as transformation-toughened zirconia and alumina and particulate- or whisker-reinforced matrices. Report predicts properly designed ceramic components viable in advanced high-temperature rocket engines and recommends future work.

  9. An Introduction to the Mechanical Properties of Ceramics

    NASA Astrophysics Data System (ADS)

    Green, David J.

    1998-09-01

    Over the past twenty-five years ceramics have become key materials in the development of many new technologies as scientists have been able to design these materials with new structures and properties. An understanding of the factors that influence their mechanical behavior and reliability is essential. This book will introduce the reader to current concepts in the field. It contains problems and exercises to help readers develop their skills. This is a comprehensive introduction to the mechanical properties of ceramics, and is designed primarily as a textbook for advanced undergraduates in materials science and engineering. It will also be of value as a supplementary text for more general courses and to industrial scientists and engineers involved in the development of ceramic-based products, materials selection and mechanical design.

  10. Structural phase transitions in yttrium under ultrahigh pressures

    NASA Astrophysics Data System (ADS)

    Samudrala, Gopi K.; Tsoi, Georgiy M.; Vohra, Yogesh K.

    2012-09-01

    X-ray diffraction studies were carried out on the rare earth metal yttrium up to 177 GPa in a diamond anvil cell at room temperature. Yttrium was compressed to 37% of its initial volume at the highest pressure. The rare earth crystal structure sequence hcp → Sm type → dhcp → mixed(dhcp + fcc) → distorted fcc (dfcc) is observed in yttrium below 50 GPa. The dfcc (hR24) phase has been observed to persist in the pressure range of 50-95 GPa. A structural transition from dfcc to a low symmetry phase has been observed in yttrium at 99 ± 4 GPa with a volume change of - 2.6%. This low symmetry phase has been identified as a monoclinic C2/m phase, which has also been observed in other rare earth elements under high pressures. The appearance of this low symmetry monoclinic phase in yttrium shows that its electronic structure under extreme conditions resembles that of heavy rare earth metals, with a significant increase in d-band character of the valence electrons and possibly some f-electron states near the Fermi level.

  11. Structural phase transitions in yttrium under ultrahigh pressures.

    PubMed

    Samudrala, Gopi K; Tsoi, Georgiy M; Vohra, Yogesh K

    2012-09-12

    X-ray diffraction studies were carried out on the rare earth metal yttrium up to 177 GPa in a diamond anvil cell at room temperature. Yttrium was compressed to 37% of its initial volume at the highest pressure. The rare earth crystal structure sequence hcp → Sm type → dhcp → mixed(dhcp + fcc) → distorted fcc (dfcc) is observed in yttrium below 50 GPa. The dfcc (hR24) phase has been observed to persist in the pressure range of 50-95 GPa. A structural transition from dfcc to a low symmetry phase has been observed in yttrium at 99 ± 4 GPa with a volume change of - 2.6%. This low symmetry phase has been identified as a monoclinic C2/m phase, which has also been observed in other rare earth elements under high pressures. The appearance of this low symmetry monoclinic phase in yttrium shows that its electronic structure under extreme conditions resembles that of heavy rare earth metals, with a significant increase in d-band character of the valence electrons and possibly some f-electron states near the Fermi level.

  12. Enhanced lithium battery with polyethylene oxide-based electrolyte containing silane-Al2 O3 ceramic filler.

    PubMed

    Zewde, Berhanu W; Admassie, Shimelis; Zimmermann, Jutta; Isfort, Christian Schulze; Scrosati, Bruno; Hassoun, Jusef

    2013-08-01

    A solid polymer electrolyte prepared by using a solvent-free, scalable technique is reported. The membrane is formed by low-energy ball milling followed by hot-pressing of dry powdered polyethylene oxide polymer, LiCF3 SO3 salt, and silane-treated Al2 O3 (Al2 O3 -ST) ceramic filler. The effects of the ceramic fillers on the properties of the ionically conducting solid electrolyte membrane are characterized by using electrochemical impedance spectroscopy, XRD, differential scanning calorimeter, SEM, and galvanostatic cycling in lithium cells with a LiFePO4 cathode. We demonstrate that the membrane containing Al2 O3 -ST ceramic filler performs well in terms of ionic conductivity, thermal properties, and lithium transference number. Furthermore, we show that the lithium cells, which use the new electrolyte together with the LiFePO4 electrode, operate within 65 and 90 °C with high efficiency and long cycle life. Hence, the Al2 O3 -ST ceramic can be efficiently used as a ceramic filler to enhance the performance of solid polymer electrolytes in lithium batteries. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Optical properties of transparent glass–ceramics containing lithium–mica nanocrystals: Crystallization effect

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

    Khani, V.; Alizadeh, P., E-mail: p-alizadeh@modares.ac.ir; Shakeri, M.S.

    2013-09-01

    Graphical abstract: Optical properties of transparent Li{sub 2}O–MgO–Al{sub 2}O{sub 3}–SiO{sub 2}–F glasses containing lithium–mica nanocrystals are studied and crystallization condition has been evaluated and optimized to produce transparent glass–ceramics. Crystallization temperatures were determined by differential thermal analysis and crystalline phases were identified and quantified by X-ray diffraction. Scanning electron microscopy was used for morphological variations and UV–vis absorption spectroscopy for comparative analysis of transparency. In order to investigate the optical properties of transparent glass–ceramics, optical band gap, Fermi energy level and Urbach energy are calculated. The results of the investigation illustrate that band gap is reduced with increases in crystallizationmore » time and temperature. Enhanced orderliness in the arrangement of atoms might be regarded as possible reasons for the above changes. - Highlights: • The optimum temperature and time of crystallization were determined. • Li–mica nanocrystals with size of <30 nm were formed using a two-step heat-treatment. • Optical band gap and Fermi energy of nanocrystalline materials decreased with increasing of crystallization temperature and time. • Urbach band tailing was decreased with increasing of crystallization condition. - Abstract: Optical properties of transparent Li{sub 2}O–MgO–Al{sub 2}O{sub 3}–SiO{sub 2}–F glasses containing lithium–mica nanocrystals were studied. The crystallization condition of these glasses was evaluated and optimized to produce transparent glass–ceramics. Crystallization temperatures were determined by differential thermal analysis and crystalline phases were identified and quantified by X-ray diffraction. Scanning electron microscopy was used to detect morphological changes and UV–vis absorption spectroscopy was used for comparative analysis of transparency. In order to investigate the optical properties

  14. Advanced Containment System

    DOEpatents

    Kostelnik, Kevin M.; Kawamura, Hideki; Richardson, John G.; Noda, Masaru

    2004-10-12

    An advanced containment system for containing buried waste and associated leachate. A trench is dug on either side of the zone of interest containing the buried waste so as to accommodate a micro tunnel boring machine. A series of small diameter tunnels are serially excavated underneath the buried waste. The tunnels are excavated by the micro tunnel boring machine at a consistent depth and are substantially parallel to each other. As tunneling progresses, steel casing sections are connected end to end in the excavated portion of the tunnel so that a steel tube is formed. Each casing section has complementary interlocking structure running its length that interlocks with complementary interlocking structure on the adjacent casing section. Thus, once the first tube is emplaced, placement of subsequent tubes is facilitated by the complementary interlocking structure on the adjacent, previously placed, casing sections.

  15. Advanced Containment System

    DOEpatents

    Kostelnik, Kevin M.; Kawamura, Hideki; Richardson, John G.; Noda, Masaru

    2005-05-24

    An advanced containment system for containing buried waste and associated leachate. A trench is dug on either side of the zone of interest containing the buried waste so as to accommodate a micro tunnel boring machine. A series of small diameter tunnels are serially excavated underneath the buried waste. The tunnels are excavated by the micro tunnel boring machine at a consistent depth and are substantially parallel to each other. As tunneling progresses, steel casing sections are connected end to end in the excavated portion of the tunnel so that a steel tube is formed. Each casing section has complementary interlocking structure running its length that interlocks with complementary interlocking structure on the adjacent casing section. Thus, once the first tube is emplaced, placement of subsequent tubes is facilitated by the complementary interlocking structure on the adjacent, previously placed, casing sections.

  16. Structure and luminescence spectra of lutetium and yttrium borates synthesized from ammonium nitrate melt

    NASA Astrophysics Data System (ADS)

    Klassen, Nikolay V.; Shmurak, Semion Z.; Shmyt'ko, Ivan M.; Strukova, Galina K.; Derenzo, Stephen E.; Weber, Marvin J.

    2005-01-01

    Lutetium and yttrium borates doped with europium, terbium, gadolinium, etc. have been synthesized by dissolving initial oxides and nitrates in ammonium nitrate melt and thermal decomposition of the solvent. Annealings in the range of 500-1100°C modified the dimensions of the grains from 2 to 3 nm to more than 100 nm. Significant dependence of the structure of lutetium borate on slight doping with rare earth ions has been found: terbium makes high-temperature vaterite phase preferential at room temperature, whereas europium stabilizes low-temperature calcite phase. Influence of the structure of the borates on the pattern of the luminescence spectra of europium dopant was observed. Possibilities for manufacturing of scintillating lutetium borate ceramics by means of this method of synthesis are discussed.

  17. New synthesis of nanopowders of proton conducting materials. A route to densified proton ceramics

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

    Khani, Zohreh; Taillades-Jacquin, Melanie; Taillades, Gilles

    2009-04-15

    Low temperature routes have been developed for the preparation of BaCe{sub 0.9}Y{sub 0.1}O{sub 2.95} (BCY10) and BaZr{sub 0.9}Y{sub 0.1}O{sub 2.95} (BZY10) in the form of nanoparticulate powders for use after densification as ceramic membranes for a proton ceramic fuel cell. These methods make use on the one hand of the chelation of metal (II), (III) and (IV) ions by acrylates (hydrogelation route) and on the other of the destabilisation and precipitation of micro-emulsions. Both routes lead to single phase yttrium doped barium cerate or zirconate perovskites, as observed by X-ray diffraction, after thermal treatment at 900 deg. C for 4more » h for BCY10 and 800 deg. C for BZY10. These temperatures, lower than those usually used for preparation of barium cerate or zirconate, lead to oxide nanoparticles of size <40 nm. Dense ceramics (>=95%) are obtained by sintering BCY10 pellets at 1350 deg. C and BZY10 pellets at 1500 deg. C for 10 h. The water uptake of compacted samples at 500 deg. C is 0.14 wt% for BCY10 and 0.26 wt% for BZY10. Total conductivities in the range 300-600 deg. C were determined using impedance spectroscopy in a humidified nitrogen atmosphere. The total conductivity was 1.8x10{sup -2} S/cm for BCY10 and 2x10{sup -3} S/cm for BZY10 at 600 deg. C. The smallest perovskite nanoparticles and highest conductivities were obtained by hydrogelation of precursor barium, zirconium, cerium and yttrium acrylates. - Graphical Abstract: Low temperature hydrogelation and micro-emulsion routes have been developed for the preparation of rare earth doped barium and zirconium cerates in the form of nanoparticulate powders for use after densification as ceramic membranes for a proton ceramic fuel cell.« less

  18. Process for separation of zirconium-88, rubidium-83 and yttrium-88

    DOEpatents

    Heaton, Richard C.; Jamriska, Sr., David J.; Taylor, Wayne A.

    1994-01-01

    A process for selective separation of strontium-82 and strontium-85 from proton irradiated molybdenum targets is provided and includes dissolving the molybdenum target in a hydrogen peroxide solution to form a first ion-containing solution, passing the first ion-containing solution through a first cationic resin whereby ions selected from the group consisting of molybdenum, niobium, technetium, selenium, vanadium, arsenic, germanium, zirconium and rubidium remain in the first ion-containing solution while ions selected from the group consisting of rubidium, zinc, beryllium, cobalt, iron, manganese, chromium, strontium, yttrium and zirconium are selectively adsorbed by the first resin, contacting the first resin with an acid solution capable of stripping adsorbed ions from the first cationic exchange resin whereby the adsorbed ions are removed from the first resin to form a second ion-containing solution, evaporating the second ion-containing solution for time sufficient to remove substantially all of the acid and water from the second ion-containing solution whereby a residue remains, dissolving the residue from the evaporated second-ion containing solution in a dilute acid to form a third ion-containing solution, said third ion-containing solution having an acid molarity adapted to permit said ions to be adsorbed by a cationic exchange resin, passing the third ion-containing solution through a second cationic resin whereby the ions are adsorbed by the second resin, contacting the second resin with a dilute sulfuric acid solution whereby the adsorbed ions selected from the group consisting of rubidium, zinc, beryllium, cobalt, iron, manganese, chromium, and zirconium are selectively removed from the second resin, and contacting the second resin with a dilute acid solution whereby the adsorbed strontium ions are selectively removed. Zirconium, rubidium, and yttrium radioisotopes can also be recovered with additional steps.

  19. Recent Progress in Using Advanced Characterization and Modeling Approaches to Study Radiation Effects in Oxide Ceramics

    DOE PAGES

    Bai, Xian-Ming

    2014-10-23

    I serve as a Guest Editor for the Nuclear Materials Committee of the TMS Structural Materials Division, and coordinated the topic ‘‘Radiation Effects in Oxide Ceramics and Novel LWR Fuels" for JOM in the December 2014 issue. I selected five articles related this topic. These articles talk about some recent progress of using advanced experimental and modeling tools to study radiation effects in oxide ceramics at atomistic scale and mesoscale. In this guest editor commentary article, I summarize the novel aspects of these papers and also provide some suggestions for future research directions.

  20. Integrated nitrogen removal biofilter system with ceramic membrane for advanced post-treatment of municipal wastewater.

    PubMed

    Son, Dong-Jin; Yun, Chan-Young; Kim, Woo-Yeol; Zhang, Xing-Ya; Kim, Dae-Gun; Chang, Duk; Sunwoo, Young; Hong, Ki-Ho

    2016-12-01

    The pre-denitrification biofilm process for nitrogen removal was combined with ceramic membrane with pore sizes of 0.05-0.1 µm as a system for advanced post-treatment of municipal wastewater. The system was operated under an empty bed hydraulic retention time of 7.8 h, recirculation ratio of 3, and transmembrane pressure of 0.47 bar. The system showed average removals of organics, total nitrogen, and solids as high as 93%, 80%, and 100%, respectively. Rapid nitrification could be achieved and denitrification was performed in the anoxic filter without external carbon supplements. The residual particulate organics and nitrogen in effluent from biofilm process could be also removed successfully through membrane filtration and the removal of total coliform was noticeably improved after membrane filtration. Thus, a system composed of the pre-denitrification biofilm process with ceramic membrane would be a compact and flexible option for advanced post-treatment of municipal wastewater.

  1. New advanced surface modification technique: titanium oxide ceramic surface implants: long-term clinical results

    NASA Astrophysics Data System (ADS)

    Szabo, Gyorgy; Kovacs, Lajos; Barabas, Jozsef; Nemeth, Zsolt; Maironna, Carlo

    2001-11-01

    The purpose of this paper is to discuss the background to advanced surface modification technologies and to present a new technique, involving the formation of a titanium oxide ceramic coating, with relatively long-term results of its clinical utilization. Three general techniques are used to modify surfaces: the addition or removal of material and the change of material already present. Surface properties can also be changed without the addition or removal of material, through the laser or electron beam thermal treatment. The new technique outlined in this paper relates to the production of a corrosion-resistant 2000-2500 A thick, ceramic oxide layer with a coherent crystalline structure on the surface of titanium implants. The layer is grown electrochemically from the bulk of the metal and is modified by heat treatment. Such oxide ceramic-coated implants have a number of advantageous properties relative to implants covered with various other coatings: a higher external hardness, a greater force of adherence between the titanium and the oxide ceramic coating, a virtually perfect insulation between the organism and the metal (no possibility of metal allergy), etc. The coated implants were subjected to various physical, chemical, electronmicroscopic, etc. tests for a qualitative characterization. Finally, these implants (plates, screws for maxillofacial osteosynthesis and dental root implants) were applied in surgical practice for a period of 10 years. Tests and the experience acquired demonstrated the good properties of the titanium oxide ceramic-coated implants.

  2. Preparation of thin ceramic films via an aqueous solution route

    DOEpatents

    Pederson, Larry R.; Chick, Lawrence A.; Exarhos, Gregory J.

    1989-01-01

    A new chemical method of forming thin ceramic films has been developed. An aqueous solution of metal nitrates or other soluble metal salts and a low molecular weight amino acid is coated onto a substrate and pyrolyzed. The amino acid serves to prevent precipitation of individual solution components, forming a very viscous, glass-like material as excess water is evaporated. Using metal nitrates and glycine, the method has been demonstrated for zirconia with various levels of yttria stabilization, for lanthanum-strontium chromites, and for yttrium-barium-copper oxide superconductors on various substrates.

  3. Development of the technology of manufacturing a ceramic tip of a resectoscope

    NASA Astrophysics Data System (ADS)

    Akhmetov, I. D.; Kashapov, R. N.; Kashapov, L. N.

    2017-09-01

    The development of medical technology is strongly correlated with the development of new materials and the technology of their processing. At the moment, the most common type of surgery is resection of the prostate gland, for its use a resectoscope is used. In this work, the problem of increasing the mechanical characteristics of ceramic tips of resectoscopes is solved. The material of yttrium stabilized zirconia has been tested and manufacturing technology based on CAD / CAM and heat treatment has been proposed

  4. Electric, Magnetic, and Magnetoelectric Properties of Yttrium-Containing BaY0.025Ti0.9625O3-SrFe12O19 Composite

    NASA Astrophysics Data System (ADS)

    Rather, Mehraj ud Din; Samad, Rubiya; Want, Basharat

    2018-03-01

    The physical properties of BaY0.025Ti0.9625O3, SrFe12O19, and 0.90BaY0.025Ti0.9625O3-0.10 SrFe12O19 composite have been studied. The proposed composite was synthesized by solid-state reaction method from yttrium barium titanate processed by solid-state reaction and strontium hexaferrite obtained by a sol-gel process. Microstructural analysis revealed monophasic grains for yttrium barium titanate phase, while loosely packed biphasic structure was observed for the composite. Powder x-ray analysis showed that the individual phases retained their crystal structure in the composite, without formation of any new additional phase. Measurement of magnetic hysteresis loops at room temperature indicated that the magnetic parameters of the composite were diluted by the presence of the ferroelectric phase. The ferroelectric hysteresis of yttrium barium titanate confirmed the ferroelectric transition at 119°C. Meanwhile, the symmetrical ferroelectric loops observed at different fields established the ferroelectric nature of the composite. Improved dielectric properties and low dielectric losses were observed due to yttrium doping in the composite. The diffuseness of the ferroelectric transitions for the composite was confirmed by the Curie-Weiss law. Activation energy calculations revealed the charge-hopping conduction mechanism in the composite. Magnetodielectric studies confirmed that the overall magnetocapacitance in the composite exhibited combined effects of magnetoresistance and magnetoelectric coupling.

  5. Plasma Synthesis and Sintering of Advanced Ceramics

    DTIC Science & Technology

    1990-09-15

    CONTENTS Page LIST OF TABLES iv OBJECTIVES 1 COLLOIDAL PLASMA PROCESSING: CONCEPTS 1 BACKGROUND 2 Ultrafine Particles 2 Colloidal Plasma 3 Particle...colloidal plasma processing of ceramics. COLLOIDAL PLASMA PROCESSING: CONCEPTS It is well known that ultrafine particles prepared in gas plasmas agglomerate...BACKGROUND Ultrafine Particles . There are well recognized advantages to using small particles in ceramic processing. The instantaneous densification

  6. Preparation of a dense, polycrystalline ceramic structure

    DOEpatents

    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.

  7. Volatile Reaction Products From Silicon-Based Ceramics in Combustion Environments Identified

    NASA Technical Reports Server (NTRS)

    Opila, Elizabeth J.

    1997-01-01

    Silicon-based ceramics and composites are prime candidates for use as components in the hot sections of advanced aircraft engines. These materials must have long-term durability in the combustion environment. Because water vapor is always present as a major product of combustion in the engine environment, its effect on the durability of silicon-based ceramics must be understood. In combustion environments, silicon-based ceramics react with water vapor to form a surface silica (SiO2) scale. This SiO2 scale, in turn, has been found to react with water vapor to form volatile hydroxides. Studies to date have focused on how water vapor reacts with high-purity silicon carbide (SiC) and SiO2 in model combustion environments. Because the combustion environment in advanced aircraft engines is expected to contain about 10-percent water vapor at 10-atm total pressure, the durability of SiC and SiO2 in gas mixtures containing 0.1- to 1-atm water vapor is of interest. The reactions of SiC and SiO2 with water vapor were monitored by measuring weight changes of sample coupons in a 0.5-atm water vapor/0.5-atm oxygen gas mixture with thermogravimetric analysis.

  8. Challenges and Opportunities in Design, Fabrication, and Testing of High Temperature Joints in Ceramics and Ceramic Composites

    NASA Technical Reports Server (NTRS)

    Singh, M.; Levine, S. R. (Technical Monitor)

    2001-01-01

    Ceramic joining has been recognized as an enabling technology for successful utilization of advanced ceramics and composite materials. A number of joint design and testing issues have been discussed for ceramic joints in silicon carbide-based ceramics and fiber-reinforced composites. These joints have been fabricated using an affordable, robust ceramic joining technology (ARCJoinT). The microstructure and good high temperature mechanical capability (compressive and flexural strengths) of ceramic joints in silicon carbide-based ceramics and composite materials are reported.

  9. Advanced Ceramic Technology for Space Applications at NASA MSFC

    NASA Technical Reports Server (NTRS)

    Alim, Mohammad A.

    2003-01-01

    The ceramic processing technology using conventional methods is applied to the making of the state-of-the-art ceramics known as smart ceramics or intelligent ceramics or electroceramics. The sol-gel and wet chemical processing routes are excluded in this investigation considering economic aspect and proportionate benefit of the resulting product. The use of ceramic ingredients in making coatings or devices employing vacuum coating unit is also excluded in this investigation. Based on the present information it is anticipated that the conventional processing methods provide identical performing ceramics when compared to that processed by the chemical routes. This is possible when sintering temperature, heating and cooling ramps, peak temperature (sintering temperature), soak-time (hold-time), etc. are considered as variable parameters. In addition, optional calcination step prior to the sintering operation remains as a vital variable parameter. These variable parameters constitute a sintering profile to obtain a sintered product. Also it is possible to obtain identical products for more than one sintering profile attributing to the calcination step in conjunction with the variables of the sintering profile. Overall, the state-of-the-art ceramic technology is evaluated for potential thermal and electrical insulation coatings, microelectronics and integrated circuits, discrete and integrated devices, etc. applications in the space program.

  10. Composite Laser Ceramics by Advanced Bonding Technology

    PubMed Central

    Kamimura, Tomosumi; Honda, Sawao

    2018-01-01

    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. PMID:29425152

  11. Treatment of wastewater containing phenol using a tubular ceramic membrane bioreactor.

    PubMed

    Ersu, C B; Ong, S K

    2008-02-01

    The performance of a membrane bioreactor (MBR) with a tubular ceramic membrane for phenol removal was evaluated under varying hydraulic retention times (HRT) and a fixed sludge residence time (SRT) of 30 days. The tubular ceramic membrane was operated with a mode of 15 minutes of filtration followed by 15 seconds of permeate backwashing at a flux of 250 l m(-2)hr(-1) along with an extended backwashing of 30 seconds every 3 hours of operation, which maintained the transmembrane pressure (TMP) below 100 kPa. Using a simulated municipal wastewater with varying phenol concentrations, the chemical oxygen demand (COD) and phenol removals observed were greater than 88% with excellent suspended solids (SS) removal of 100% at low phenol concentrations (approx. 100 mg l(-1) of phenol). Step increases in phenol concentration showed that inhibition was observed between 600 to 800 mg l(-1) of phenol with decreased sludge production rate, mixed liquor suspended solids (MLSS) concentration, and removal performance. The sludge volume index (SVI) of the biomass increased to about 450 ml g(-1) for a phenol input concentration of 800 mg l(-1). When the phenol concentration was decreased to 100 mg l(-1), the ceramic tubular MBR was found to recover rapidly indicating that the MBR is a robust system retaining most of the biomass. Experimental runs using wastewater containing phenol indicated that the MBR can be operated safely without upsets for concentrations up to 600 mg l(-1) of phenol at 2-4 hours HRT and 30 days SRT.

  12. Ultrasonic and radiographic evaluation of advanced aerospace materials: Ceramic composites

    NASA Technical Reports Server (NTRS)

    Generazio, Edward R.

    1990-01-01

    Two conventional nondestructive evaluation techniques were used to evaluate advanced ceramic composite materials. It was shown that neither ultrasonic C-scan nor radiographic imaging can individually provide sufficient data for an accurate nondestructive evaluation. Both ultrasonic C-scan and conventional radiographic imaging are required for preliminary evaluation of these complex systems. The material variations that were identified by these two techniques are porosity, delaminations, bond quality between laminae, fiber alignment, fiber registration, fiber parallelism, and processing density flaws. The degree of bonding between fiber and matrix cannot be determined by either of these methods. An alternative ultrasonic technique, angular power spectrum scanning (APSS) is recommended for quantification of this interfacial bond.

  13. Intense blue up-conversion luminescence in Tm 3+/Yb 3+ codoped oxyfluoride glass-ceramics containing β-PbF 2 nanocrystals

    NASA Astrophysics Data System (ADS)

    Zhang, Junjie; Duan, Zhongchao; He, Dongbing; Dai, Shixun; Zhang, Liyan; Hu, Lili

    2005-12-01

    Up-conversion luminescence properties of a Tm 3+/Yb 3+ codoped oxyfluoride glass-ceramics under 980 nm excitation are investigated. Intense blue emission centered at 476 nm, corresponding to 1G 4 → 3H 6 transitions of Tm 3+ was simultaneously observed in the transparent oxyfluoride glass ceramics at room temperature. The intensity of the blue up-conversion luminescence in a 1 mol% YbF 3-containing glass-ceramic was found to be about 40 times stronger than that in the precursor oxyfluoride glass. The reason for the intense Tm 3+ up-conversion luminescence in the oxyfluoride glass-ceramics is discussed. The dependence of up-conversion intensities on excitation power and possible up-conversion mechanism are also evaluated.

  14. Intense blue up-conversion luminescence in Tm3+/Yb3+ codoped oxyfluoride glass-ceramics containing beta-PbF2 nanocrystals.

    PubMed

    Zhang, Junjie; Duan, Zhongchao; He, Dongbing; Dai, Shixun; Zhang, Liyan; Hu, Lili

    2005-12-01

    Up-conversion luminescence properties of a Tm3+/Yb3+ codoped oxyfluoride glass-ceramics under 980 nm excitation are investigated. Intense blue emission centered at 476 nm, corresponding to 1G4-->3H6 transitions of Tm3+ was simultaneously observed in the transparent oxyfluoride glass ceramics at room temperature. The intensity of the blue up-conversion luminescence in a 1 mol% YbF3-containing glass-ceramic was found to be about 40 times stronger than that in the precursor oxyfluoride glass. The reason for the intense Tm3+ up-conversion luminescence in the oxyfluoride glass-ceramics is discussed. The dependence of up-conversion intensities on excitation power and possible up-conversion mechanism are also evaluated.

  15. Process for strengthening silicon based ceramics

    DOEpatents

    Kim, Hyoun-Ee; Moorhead, A. J.

    1993-01-01

    A process for strengthening silicon based ceramic monolithic materials and omposite materials that contain silicon based ceramic reinforcing phases that requires that the ceramic be exposed to a wet hydrogen atmosphere at about 1400.degree. C. The process results in a dense, tightly adherent silicon containing oxide layer that heals, blunts , or otherwise negates the detrimental effect of strength limiting flaws on the surface of the ceramic body.

  16. Process for strengthening silicon based ceramics

    DOEpatents

    Kim, Hyoun-Ee; Moorhead, A. J.

    1993-04-06

    A process for strengthening silicon based ceramic monolithic materials and omposite materials that contain silicon based ceramic reinforcing phases that requires that the ceramic be exposed to a wet hydrogen atmosphere at about 1400.degree. C. The process results in a dense, tightly adherent silicon containing oxide layer that heals, blunts , or otherwise negates the detrimental effect of strength limiting flaws on the surface of the ceramic body.

  17. Tests of NASA ceramic thermal barrier coating for gas-turbine engines

    NASA Technical Reports Server (NTRS)

    Liebert, C. H.

    1979-01-01

    A NASA ceramic thermal barrier coating (TBC) system was tested by industrial and governmental organizations for a variety of aeronautical marine, and ground-based gas-turbine engine applications. This TBC is a two-layer system with a bond coating of nickel-chromium-aluminum-yttrium (Ni-16Cr-6Al-0.6Y, in wt %) and a ceramic coating of yttria stabilized zirconia (ZrO2-12Y2O3, in wt %). Tests (Liebert and Stenka, 1979) have been conducted to determine corrosion resistance, thermal protection, durability, thermal conductivity, and fatigue characteristics. The information presented covers some of the significant test results obtained on the first three items. The information also includes photographs of coated parts after tests, measurements of coating loss, amount of metal wall temperature reduction when the TBC is used, and extent of base metal corrosion.

  18. The synthesis of ZrO2-Y2O3 ceramic fibers by the method of impregnation of viscous threads

    NASA Astrophysics Data System (ADS)

    Titova, S. M.; Obabkov, N. V.; Zakirova, A. F.; Zakirov, I. F.; Dokuchaev, V. S.; Shak, A. V.

    2017-09-01

    The possibility of synthesis of ZrO2-Y2O3 oxide fibers and their applicatiuon for reinforcing porous ceramics of the same composition was investigated. Ceramic fibers were obtained by impregnating viscose strings with solutions of zirconyl and yttrium nitrates. The method allows synthesis of the fibers with a diameter of 400 µm and length of 5 to 20 mm. The strength of the synthesized fibers was determined. The maximum tensile strength (132.45 MPa) was demonstrated by fibers obtained with a working solution concentration of 500 g oxides/L. Repeated impregnation of the viscose yarn led to an increase in the strength of the fibers to 205 MPa. Ceramic fibers can be used as reinforcing elements of oxide ceramics. The bending strength of the reinforced ceramics was 3 MPa. After 10 cycles of thermal cycling (heating to 1100 °C and cooling in water) the bending strength was reduced to 1 MPa.

  19. Clinical application of bio ceramics

    NASA Astrophysics Data System (ADS)

    Anu, Sharma; Gayatri, Sharma

    2016-05-01

    Ceramics are the inorganic crystalline material. These are used in various field such as biomedical, electrical, electronics, aerospace, automotive and optical etc. Bio ceramics are the one of the most active areas of research. Bio ceramics are the ceramics which are biocompatible. The unique properties of bio ceramics make them an attractive option for medical applications and offer some potential advantages over other materials. During the past three decades, a number of major advances have been made in the field of bio ceramics. This review focuses on the use of these materials in variety of clinical scenarios.

  20. Clinical application of bio ceramics

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

    Anu, Sharma, E-mail: issaranu@gmail.com; Gayatri, Sharma, E-mail: sharmagayatri@gmail.com

    Ceramics are the inorganic crystalline material. These are used in various field such as biomedical, electrical, electronics, aerospace, automotive and optical etc. Bio ceramics are the one of the most active areas of research. Bio ceramics are the ceramics which are biocompatible. The unique properties of bio ceramics make them an attractive option for medical applications and offer some potential advantages over other materials. During the past three decades, a number of major advances have been made in the field of bio ceramics. This review focuses on the use of these materials in variety of clinical scenarios.

  1. Effect of in vitro aging on the flexural strength and probability to fracture of Y-TZP zirconia ceramics for all-ceramic restorations.

    PubMed

    Siarampi, Eleni; Kontonasaki, Eleana; Andrikopoulos, Konstantinos S; Kantiranis, Nikolaos; Voyiatzis, George A; Zorba, Triantafillia; Paraskevopoulos, Konstantinos M; Koidis, Petros

    2014-12-01

    Dental zirconia restorations should present long-term clinical survival and be in service within the oral environment for many years. However, low temperature degradation could affect their mechanical properties and survival. The aim of this study was to investigate the effect of in vitro aging on the flexural strength of yttrium-stabilized (Y-TZP) zirconia ceramics for ceramic restorations. One hundred twenty bar-shaped specimens were prepared from two ceramics (ZENO Zr (WI) and IPS e.max(®) ZirCAD (IV)), and loaded until fracture according to ISO 6872. The specimens from each ceramic (nx=60) were divided in three groups (control, aged for 5h, aged for 10h). One-way ANOVA was used to assess statistically significant differences among flexural strength values (P<0.05). The variability of the flexural strength values was analyzed using the two-parameter Weibull distribution function, which was applied for the estimation of Weibull modulus (m) and characteristic strength (σ0). The crystalline phase polymorphs of the materials (tetragonal, t, and monoclinic, m, zirconia) were investigated by X-ray diffraction (XRD) analysis, Raman spectroscopy and Fourier transform infrared (FTIR) spectroscopy. A slight increase of the flexural strength after 5h, and a decrease after 10h of aging, was recorded for both ceramics, however statistically significant was for the WI group (P<0.05). Both ceramics presented a t→m phase transformation, with the m-phase increasing from 4 to 5% at 5h to around 15% after 10h. The significant reduction of the flexural strength after 10h of in vitro aging, suggests high fracture probability for one of the zirconia ceramics tested. Copyright © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  2. Sintering and microstructure of silicon carbide ceramic with Y3Al5O12 added by sol-gel method*

    PubMed Central

    Guo, Xing-zhong; Yang, Hui

    2005-01-01

    Silicon carbide (SiC) ceramic with YAG (Y3Al5O12) additive added by sol-gel method was liquid-phase sintered at different sintering temperatures, and the sintering mechanism and microstructural characteristics of resulting silicon carbide ceramics were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and elemental distribution of surface (EDS). YAG (yttrium aluminum garnet) phase formed before the sintering and its uniform distribution in the SiC/YAG composite powder decreased the sintering temperature and improved the densification of SiC ceramic. The suitable sintering temperature was 1860 °C with the specimen sintered at this temperature having superior sintering and mechanical properties, smaller crystal size and fewer microstructure defects. Three characteristics of improved toughness of SiC ceramic with YAG added by sol-gel method were microstructural densification, main-crack deflection and crystal ‘bridging’. PMID:15682507

  3. Ceramic Coatings for Corrosion Resistant Nuclear Waste Container Evaluated in Simulated Ground Water at 90?C

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

    Haslam, J J; Farmer, J C

    2004-03-31

    Ceramic materials have been considered as corrosion resistant coatings for nuclear waste containers. Their suitability can be derived from the fully oxidized state for selected metal oxides. Several types of ceramic coatings applied to plain carbon steel substrates by thermal spray techniques have been exposed to 90 C simulated ground water for nearly 6 years. In some cases no apparent macroscopic damage such as coating spallation was observed in coatings. Thermal spray processes examined in this work included plasma spray, High Velocity Oxy Fuel (HVOF), and Detonation Gun. Some thermal spray coatings have demonstrated superior corrosion protection for the plainmore » carbon steel substrate. In particular the HVOF and Detonation Gun thermal spray processes produced coatings with low connected porosity, which limited the growth rate of corrosion products. It was also demonstrated that these coatings resisted spallation of the coating even when an intentional flaw (which allowed for corrosion of the carbon steel substrate underneath the ceramic coating) was placed in the coating. A model for prediction of the corrosion protection provided by ceramic coatings is presented. The model includes the effect of the morphology and amount of the porosity within the thermal spray coating and provides a prediction of the exposure time needed to produce a crack in the ceramic coating.« less

  4. Rare earths, the lanthanides, yttrium and scandium

    USGS Publications Warehouse

    Bedinger, G.; Bleiwas, D.

    2012-01-01

    In 2011, rare earths were recovered from bastnasite concentrates at the Mountain Pass Mine in California. Consumption of refined rare-earth products decreased in 2011 from 2010. U.S. rare-earth imports originated primarily from China, with lesser amounts from Austria, Estonia, France and Japan. The United States imported all of its demand for yttrium metal and yttrium compounds, with most of it originating from China. Scandium was imported in various forms and processed domestically.

  5. New synthesis of nanopowders of proton conducting materials. A route to densified proton ceramics

    NASA Astrophysics Data System (ADS)

    Khani, Zohreh; Taillades-Jacquin, Mélanie; Taillades, Gilles; Marrony, Mathieu; Jones, Deborah J.; Rozière, Jacques

    2009-04-01

    Low temperature routes have been developed for the preparation of BaCe 0.9Y 0.1O 2.95 (BCY10) and BaZr 0.9Y 0.1O 2.95 (BZY10) in the form of nanoparticulate powders for use after densification as ceramic membranes for a proton ceramic fuel cell. These methods make use on the one hand of the chelation of metal (II), (III) and (IV) ions by acrylates (hydrogelation route) and on the other of the destabilisation and precipitation of micro-emulsions. Both routes lead to single phase yttrium doped barium cerate or zirconate perovskites, as observed by X-ray diffraction, after thermal treatment at 900 °C for 4 h for BCY10 and 800 °C for BZY10. These temperatures, lower than those usually used for preparation of barium cerate or zirconate, lead to oxide nanoparticles of size <40 nm. Dense ceramics (⩾95%) are obtained by sintering BCY10 pellets at 1350 °C and BZY10 pellets at 1500 °C for 10 h. The water uptake of compacted samples at 500 °C is 0.14 wt% for BCY10 and 0.26 wt% for BZY10. Total conductivities in the range 300-600 °C were determined using impedance spectroscopy in a humidified nitrogen atmosphere. The total conductivity was 1.8×10 -2 S/cm for BCY10 and 2×10 -3 S/cm for BZY10 at 600 °C. The smallest perovskite nanoparticles and highest conductivities were obtained by hydrogelation of precursor barium, zirconium, cerium and yttrium acrylates.

  6. Two-Step Sintering Behavior of Sol-Gel Derived Dense and Submicron-Grained YIG Ceramics

    NASA Astrophysics Data System (ADS)

    Chen, Ruoyuan; Zhou, Jijun; Zheng, Liang; Zheng, Hui; Zheng, Peng; Ying, Zhihua; Deng, Jiangxia

    2018-04-01

    In this work, dense and submicron-grain yttrium iron garnet (YIG, Y3Fe5O12) ceramics were fabricated by a two-step sintering (TSS) method using nano-size YIG powder prepared by a citrate sol-gel method. The densification, microstructure, magnetic properties and ferromagnetic resonance (FMR) linewidth of the ceramics were investigated. The sample prepared at 1300°C in T 1, 1225°C in T 2 and 18 h holding time has a density higher than 98% of the theoretical value and exhibits a homogeneous microstructure with fine grain size (0.975 μm). In addition, the saturation magnetization ( M S) of this sample reaches 27.18 emu/g. High density and small grain size can also achieve small FMR linewidth. Consequently, these results show that the sol-gel process combined with the TSS process can effectively suppress grain-boundary migration while maintaining active grain-boundary diffusion to obtain dense and fine-grained YIG ceramics with appropriate magnetic properties.

  7. Heat treatment of transparent Yb:YAG and YAG ceramics and its influence on laser performance

    NASA Astrophysics Data System (ADS)

    Fujioka, Kana; Mochida, Tetsuo; Fujimoto, Yasushi; Tokita, Shigeki; Kawanaka, Junji; Maruyama, Momoko; Sugiyama, Akira; Miyanaga, Noriaki

    2018-05-01

    Composite transparent ceramic materials are promising for improving the performance of high-average-power lasers. A combination of room-temperature bonding via surface treatment by a fast atom beam and diffusion bonding via heating, which effectively controls the ion diffusion distance near the interface, makes the laser materials suitable for a variety of oscillator/amplifier. During the heat treatment of yttrium aluminum garnet (YAG) ceramics, the Si ions in the solid solution of the sintering aid incorporated within the grains were seen to segregate at the grain boundary, resulting in an increase of scattering sites. The number density and size of the scattering sites strongly depended on the post-heating temperature rather than the heating time. Specifically, heating at 1300 °C did not affect the transmittance of the YAG ceramic, whereas both the size and number of scattering sites substantially increased with a heat treatment at 1400 °C. The laser oscillation experiment using cryogenically-cooled Yb:YAG ceramics exhibited heating temperature dependence of the slope efficiency owing to the increasing scattering loss.

  8. Method for Waterproofing Ceramic Materials

    NASA Technical Reports Server (NTRS)

    Cagliostro, Domenick E. (Inventor); Hsu, Ming-Ta S. (Inventor)

    1998-01-01

    Hygroscopic ceramic materials which are difficult to waterproof with a silane, substituted silane or silazane waterproofing agent, such as an alumina containing fibrous, flexible and porous, fibrous ceramic insulation used on a reentry space vehicle, are rendered easy to waterproof if the interior porous surface of the ceramic is first coated with a thin coating of silica. The silica coating is achieved by coating the interior surface of the ceramic with a silica precursor converting the precursor to silica either in-situ or by oxidative pyrolysis and then applying the waterproofing agent to the silica coated ceramic. The silica precursor comprises almost any suitable silicon containing material such as a silane, silicone, siloxane, silazane and the like applied by solution, vapor deposition and the like. If the waterproofing is removed by e.g., burning, the silica remains and the ceramic is easily rewaterproofed. An alumina containing TABI insulation which absorbs more that five times its weight of water, absorbs less than 10 wt. % water after being waterproofed according to the method of the invention.

  9. Ceramic material suitable for repair of a space vehicle component in a microgravity and vacuum environment, method of making same, and method of repairing a space vehicle component

    NASA Technical Reports Server (NTRS)

    Riedell, James A. (Inventor); Easler, Timothy E. (Inventor)

    2009-01-01

    A precursor of a ceramic adhesive suitable for use in a vacuum, thermal, and microgravity environment. The precursor of the ceramic adhesive includes a silicon-based, preceramic polymer and at least one ceramic powder selected from the group consisting of aluminum oxide, aluminum nitride, boron carbide, boron oxide, boron nitride, hafnium boride, hafnium carbide, hafnium oxide, lithium aluminate, molybdenum silicide, niobium carbide, niobium nitride, silicon boride, silicon carbide, silicon oxide, silicon nitride, tin oxide, tantalum boride, tantalum carbide, tantalum oxide, tantalum nitride, titanium boride, titanium carbide, titanium oxide, titanium nitride, yttrium oxide, zirconium diboride, zirconium carbide, zirconium oxide, and zirconium silicate. Methods of forming the ceramic adhesive and of repairing a substrate in a vacuum and microgravity environment are also disclosed, as is a substrate repaired with the ceramic adhesive.

  10. Flash sintering of ceramic materials

    NASA Astrophysics Data System (ADS)

    Dancer, C. E. J.

    2016-10-01

    During flash sintering, ceramic materials can sinter to high density in a matter of seconds while subjected to electric field and elevated temperature. This process, which occurs at lower furnace temperatures and in shorter times than both conventional ceramic sintering and field-assisted methods such as spark plasma sintering, has the potential to radically reduce the power consumption required for the densification of ceramic materials. This paper reviews the experimental work on flash sintering methods carried out to date, and compares the properties of the materials obtained to those produced by conventional sintering. The flash sintering process is described for oxides of zirconium, yttrium, aluminium, tin, zinc, and titanium; silicon and boron carbide, zirconium diboride, materials for solid oxide fuel applications, ferroelectric materials, and composite materials. While experimental observations have been made on a wide range of materials, understanding of the underlying mechanisms responsible for the onset and latter stages of flash sintering is still elusive. Elements of the proposed theories to explain the observed behaviour include extensive Joule heating throughout the material causing thermal runaway, arrested by the current limitation in the power supply, and the formation of defect avalanches which rapidly and dramatically increase the sample conductivity. Undoubtedly, the flash sintering process is affected by the electric field strength, furnace temperature and current density limit, but also by microstructural features such as the presence of second phase particles or dopants and the particle size in the starting material. While further experimental work and modelling is still required to attain a full understanding capable of predicting the success of the flash sintering process in different materials, the technique non-etheless holds great potential for exceptional control of the ceramic sintering process.

  11. The Role of Ceramics in a Resurgent Nuclear Industry

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

    Marra, J

    2006-02-28

    With fuel oil and natural gas prices near record highs and worldwide energy demands increasing at an alarming rate, there is growing interest in revitalization of the nuclear power industry within the United States and across the globe. Ceramic materials have long played a very important part in the commercial nuclear industry with applications throughout the entire fuel cycle; from fuel fabrication to waste stabilization. As the international community begins to look at advanced fuel cycles that minimize waste and increase proliferation resistance, ceramic materials will play an even larger role. Many of the advanced reactor concepts being evaluated operatemore » at high-temperature requiring the use of durable, heat-resistant materials. Ceramic fuels are being investigated for a variety of Generation IV reactor concepts. These include the traditional TRISO-coated particles as well as advanced inert-matrix fuels. In order to minimize wastes and legacy materials, ceramic processes are also being applied to fuel reprocessing operations. Ceramic materials continue to provide a vital contribution in ''closing the fuel cycle'' by stabilization of associated low-level and high-level wastes in highly durable grout, ceramics, and glass. In the next five years, programs that are currently in the conceptual phase will begin laboratory- and engineering-scale demonstrations. This will require production-scale demonstrations of several ceramic technologies from fuel form development to advanced stabilization methods. Within the next five to ten years, these demonstrations will move to even larger scales and will also include radioactive demonstrations of these advanced technologies. These radioactive demonstrations are critical to program success and will require advances in ceramic materials associated with nuclear energy applications.« less

  12. Size-dependent cytotoxicity of yttrium oxide nanoparticles on primary osteoblasts in vitro

    NASA Astrophysics Data System (ADS)

    Zhou, Guoqiang; Li, Yunfei; Ma, Yanyan; Liu, Zhu; Cao, Lili; Wang, Da; Liu, Sudan; Xu, Wenshi; Wang, Wenying

    2016-05-01

    Yttrium oxide nanoparticles are an excellent host material for the rare earth metals and have high luminescence efficiency providing a potential application in photodynamic therapy and biological imaging. In this study, the effects of yttrium oxide nanoparticles with four different sizes were investigated using primary osteoblasts in vitro. The results demonstrated that the cytotoxicity generated by yttrium oxide nanoparticles depended on the particle size, and smaller particles possessed higher toxicological effects. For the purpose to elucidate the relationship between reactive oxygen species generation and cell damage, cytomembrane integrity, intracellular reactive oxygen species level, mitochondrial membrane potential, cell apoptosis rate, and activity of caspase-3 in cells were then measured. Increased reactive oxygen species level was also observed in a size-dependent way. Thus, our data demonstrated that exposure to yttrium oxide nanoparticles resulted in a size-dependent cytotoxicity in cultured primary osteoblasts, and reactive oxygen species generation should be one possible damage pathway for the toxicological effects produced by yttrium oxide particles. The results may provide useful information for more rational applications of yttrium oxide nanoparticles in the future.

  13. High Energy Failure Containment for Spacecraft

    NASA Technical Reports Server (NTRS)

    Pektas, Pete; Baker, Christopher

    2011-01-01

    Objective: The objective of this paper will be to investigate advancements and any commonality between spacecraft debris containment and the improvements being made in ballistic protection. Scope: This paper will focus on cross application of protection devices and methods, and how they relate to protecting humans from failures in spacecraft. The potential gain is to reduce the risk associated with hardware failure, while decreasing the weight and size of energy containment methods currently being used by the government and commercial industry. Method of Approach: This paper will examine testing that has already been accomplished in regards to the failure of high energy rotating hardware and compare it to advancements in ballistic protection. Examples are: DOT research and testing of turbine containment as documented in DOT/FAA/AR-96/110, DOT/FAA/AR-97/82, DOT/FAA/AR-98/22. It will also look at work accomplished by companies such as ApNano and IBD Deisenroth in the development of nano ceramics and nanometric steels. Other forms of energy absorbent materials and composites will also be considered and discussed. New Advances in State of the Art: There have been numerous advances in technology in regards to high energy debris containment and in the similar field of ballistic protection. This paper will discuss methods such as using impregnated or dry Kevlar, ceramic, and nano-technology which have been successfully tested but are yet to be utilized in spacecraft. Reports on tungsten disulfide nanotubes claim that they are 4-5 times stronger than steel and reports vary about the magnitude increase over Kevlar, but it appears to be somewhere in the range of 2-6 times stronger. This technology could also have applications in the protection of pressure vessels, motor housings, and hydraulic component failures.

  14. Glass-ceramic optical fiber containing Ba2TiSi2O8 nanocrystals for frequency conversion of lasers

    NASA Astrophysics Data System (ADS)

    Fang, Zaijin; Xiao, Xusheng; Wang, Xin; Ma, Zhijun; Lewis, Elfed; Farrell, Gerald; Wang, Pengfei; Ren, Jing; Guo, Haitao; Qiu, Jianrong

    2017-03-01

    A glass-ceramic optical fiber containing Ba2TiSi2O8 nanocrystals fabricated using a novel combination of the melt-in-tube method and successive heat treatment is reported for the first time. For the melt-in-tube method, fibers act as a precursor at the drawing temperature for which the cladding glass is softened while the core glass is melted. It is demonstrated experimentally that following heat treatment, Ba2TiSi2O8 nanocrystals with diameters below 10 nm are evenly distributed throughout the fiber core. Comparing to the conventional rod-in-tube method, the melt-in-tube method is superior in terms of controllability of crystallization to allow for the fabrication of low loss glass-ceramic fibers. When irradiated using a 1030 nm femtosecond laser, an enhanced green emission at a wavelength of 515 nm is observed in the glass-ceramic fiber, which demonstrates second harmonic generation of a laser action in the fabricated glass-ceramic fibers. Therefore, this new glass-ceramic fiber not only provides a highly promising development for frequency conversion of lasers in all optical fiber based networks, but the melt-in-tube fabrication method also offers excellent opportunities for fabricating a wide range of novel glass-ceramic optical fibers for multiple future applications including fiber telecommunications and lasers.

  15. Glass-ceramic optical fiber containing Ba2TiSi2O8 nanocrystals for frequency conversion of lasers

    PubMed Central

    Fang, Zaijin; Xiao, Xusheng; Wang, Xin; Ma, Zhijun; Lewis, Elfed; Farrell, Gerald; Wang, Pengfei; Ren, Jing; Guo, Haitao; Qiu, Jianrong

    2017-01-01

    A glass-ceramic optical fiber containing Ba2TiSi2O8 nanocrystals fabricated using a novel combination of the melt-in-tube method and successive heat treatment is reported for the first time. For the melt-in-tube method, fibers act as a precursor at the drawing temperature for which the cladding glass is softened while the core glass is melted. It is demonstrated experimentally that following heat treatment, Ba2TiSi2O8 nanocrystals with diameters below 10 nm are evenly distributed throughout the fiber core. Comparing to the conventional rod-in-tube method, the melt-in-tube method is superior in terms of controllability of crystallization to allow for the fabrication of low loss glass-ceramic fibers. When irradiated using a 1030 nm femtosecond laser, an enhanced green emission at a wavelength of 515 nm is observed in the glass-ceramic fiber, which demonstrates second harmonic generation of a laser action in the fabricated glass-ceramic fibers. Therefore, this new glass-ceramic fiber not only provides a highly promising development for frequency conversion of lasers in all optical fiber based networks, but the melt-in-tube fabrication method also offers excellent opportunities for fabricating a wide range of novel glass-ceramic optical fibers for multiple future applications including fiber telecommunications and lasers. PMID:28358045

  16. Glass-ceramic optical fiber containing Ba2TiSi2O8 nanocrystals for frequency conversion of lasers.

    PubMed

    Fang, Zaijin; Xiao, Xusheng; Wang, Xin; Ma, Zhijun; Lewis, Elfed; Farrell, Gerald; Wang, Pengfei; Ren, Jing; Guo, Haitao; Qiu, Jianrong

    2017-03-30

    A glass-ceramic optical fiber containing Ba 2 TiSi 2 O 8 nanocrystals fabricated using a novel combination of the melt-in-tube method and successive heat treatment is reported for the first time. For the melt-in-tube method, fibers act as a precursor at the drawing temperature for which the cladding glass is softened while the core glass is melted. It is demonstrated experimentally that following heat treatment, Ba 2 TiSi 2 O 8 nanocrystals with diameters below 10 nm are evenly distributed throughout the fiber core. Comparing to the conventional rod-in-tube method, the melt-in-tube method is superior in terms of controllability of crystallization to allow for the fabrication of low loss glass-ceramic fibers. When irradiated using a 1030 nm femtosecond laser, an enhanced green emission at a wavelength of 515 nm is observed in the glass-ceramic fiber, which demonstrates second harmonic generation of a laser action in the fabricated glass-ceramic fibers. Therefore, this new glass-ceramic fiber not only provides a highly promising development for frequency conversion of lasers in all optical fiber based networks, but the melt-in-tube fabrication method also offers excellent opportunities for fabricating a wide range of novel glass-ceramic optical fibers for multiple future applications including fiber telecommunications and lasers.

  17. Advanced Environmental Barrier Coating Development for SiC-SiC Ceramic Matrix Composite Components

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Harder, Bryan; Bhatt, Ramakrishna; Kiser, Doug; Wiesner, Valerie L.

    2016-01-01

    This presentation reviews the NASA advanced environmental barrier coating (EBC) system development for SiCSiC Ceramic Matrix Composite (CMC) components for next generation turbine engines. The emphasis has been placed on the current design challenges of the 2700F environmental barrier coatings; coating processing and integration with SiCSiC CMCs and component systems; and performance evaluation and demonstration of EBC-CMC systems. This presentation also highlights the EBC-CMC system temperature capability and durability improvements through advanced compositions and architecture designs, as shown in recent simulated engine high heat flux, combustion environment, in conjunction with mechanical creep and fatigue loading testing conditions.

  18. Process for making ultra-fine ceramic particles

    DOEpatents

    Stangle, Gregory C.; Venkatachari, Koththavasal R.; Ostrander, Steven P.; Schulze, Walter A.

    1995-01-01

    A process for producing ultra-fine ceramic particles in which droplets are formed from a ceramic precursor mixture containing a metal cation, a nitrogen-containing fuel, a solvent, and an anion capable of participating in an anionic oxidation-reduction reaction with the nitrogen containing fuel. The nitrogen-containing fuel contains at least three nitrogen atoms, at least one oxygen atom, and at least one carbon atom. The ceramic precursor mixture is dried to remove at least 85 weight percent of the solvent, and the dried mixture is then ignited to form a combusted powder.

  19. Quaternary Polymer Electrolytes Containing an Ionic Liquid and a Ceramic Filler.

    PubMed

    Sharova, Varvara; Kim, Guk-Tae; Giffin, Guinevere A; Lex-Balducci, Alexandra; Passerini, Stefano

    2016-07-01

    In this work, the individual and combined effects of an ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide and ceramic filler silicon dioxide on the thermal and electrochemical properties of poly(ethylene oxide) electrolytes have been investigated. The electrolyte containing both components has the lowest glass transition (-60 °C) and melting temperatures (27 °C), the highest conductivity at any investigated temperature, and the highest limiting current density (at 40 °C). This solid polymer electrolyte also exhibits the best long-term cycling performance in Li/LiFePO4 cells. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. [Ceramic-on-ceramic bearings in total hip arthroplasty (THA)].

    PubMed

    Sentürk, U; Perka, C

    2015-04-01

    The main reason for total hip arthroplasty (THA) revision is the wear-related aseptic loosening. Younger and active patients after total joint replacement create high demands, in particular, on the bearings. The progress, especially for alumina ceramic-on-ceramic bearings and mixed ceramics have solved many problems of the past and lead to good in vitro results. Modern ceramics (alumina or mixed ceramics containing alumina) are extremely hard, scratch-resistant, biocompatible, offer a low coefficient of friction, superior lubrication and have the lowest wear rates in comparison to all other bearings in THA. The disadvantage of ceramic is the risk of material failure, i.e., of ceramic fracture. The new generation of mixed ceramics (delta ceramic), has reduced the risk of head fractures to 0.03-0.05 %, but the risk for liner fractures remains unchanged at about 0.02 %. Assuming a non-impinging component implantation, ceramic-on-ceramic bearings have substantial advantages over all other bearings in THA. Due to the superior hardness, ceramic bearings produce less third body wear and are virtually impervious to damage from instruments during the implantation process. A specific complication for ceramic-on-ceramic bearings is "squeaking". The high rate of reported squeaking (0.45 to 10.7 %) highlights the importance of precise implant positioning and the stem and patient selection. With precise implant positioning this problem is rare with many implant designs and without clinical relevance. The improved tribology and the presumable resulting implant longevity make ceramic-on-ceramic the bearing of choice for young and active patients. Georg Thieme Verlag KG Stuttgart · New York.

  1. A new classification system for all-ceramic and ceramic-like restorative materials.

    PubMed

    Gracis, Stefano; Thompson, Van P; Ferencz, Jonathan L; Silva, Nelson R F A; Bonfante, Estevam A

    2015-01-01

    Classification systems for all-ceramic materials are useful for communication and educational purposes and warrant continuous revisions and updates to incorporate new materials. This article proposes a classification system for ceramic and ceramic-like restorative materials in an attempt to systematize and include a new class of materials. This new classification system categorizes ceramic restorative materials into three families: (1) glass-matrix ceramics, (2) polycrystalline ceramics, and (3) resin-matrix ceramics. Subfamilies are described in each group along with their composition, allowing for newly developed materials to be placed into the already existing main families. The criteria used to differentiate ceramic materials are based on the phase or phases present in their chemical composition. Thus, an all-ceramic material is classified according to whether a glass-matrix phase is present (glass-matrix ceramics) or absent (polycrystalline ceramics) or whether the material contains an organic matrix highly filled with ceramic particles (resin-matrix ceramics). Also presented are the manufacturers' clinical indications for the different materials and an overview of the different fabrication methods and whether they are used as framework materials or monolithic solutions. Current developments in ceramic materials not yet available to the dental market are discussed.

  2. Advanced Environmental Barrier Coating Development for SiC/SiC Ceramic Matrix Composites: NASA's Perspectives

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming

    2016-01-01

    This presentation reviews NASA environmental barrier coating (EBC) system development programs and the coating materials evolutions for protecting the SiC/SiC Ceramic Matrix Composites in order to meet the next generation engine performance requirements. The presentation focuses on several generations of NASA EBC systems, EBC-CMC component system technologies for SiC/SiC ceramic matrix composite combustors and turbine airfoils, highlighting the temperature capability and durability improvements in simulated engine high heat flux, high pressure, high velocity, and with mechanical creep and fatigue loading conditions. The current EBC development emphasis is placed on advanced NASA 2700F candidate environmental barrier coating systems for SiC/SiC CMCs, their performance benefits and design limitations in long-term operation and combustion environments. Major technical barriers in developing environmental barrier coating systems, the coating integrations with next generation CMCs having the improved environmental stability, erosion-impact resistance, and long-term fatigue-environment system durability performance are described. The research and development opportunities for advanced turbine airfoil environmental barrier coating systems by utilizing improved compositions, state-of-the-art processing methods, and simulated environment testing and durability modeling are discussed.

  3. Advanced CerMet ceramic composites for medical applications.

    PubMed

    Dittmer, Robert; Schaefer, Christian M; Fischer, Jean-Francois; Hausch, Ulrich; Troetzschel, Jens; Specht, Heiko

    2017-11-01

    Implantable active devices such as pacemakers are facing rigorous requirements. Because they reside within the body for years, materials applied in this surrounding must exhibit biocompatibility and extraordinary reliability. They also have to provide a number of functional properties. In this work we present a method that enables the realization of a highly complex profile of properties by means of a dual composite approach. Using multilayer technology, an electrical conductor is embedded into a ceramic matrix, thus, creating conductive paths that are insulated from each other. In addition to this macroscopically hybrid architecture, this approach features a second composite aspect: the conductor is not composed of a single metallic phase, but is a ceramic-metal mixture. Owing to its interpenetrating microstructure, this CerMet allows for a strong and hermetic integration of the conductor into the ceramic matrix otherwise impossible due to mismatch in thermal expansion. In fact, the CerMet ceramic composite exhibits a higher strength than the pure ceramic as revealed by a three-point bending test study. At the same time, the CerMet offers high and virtually metal-like conductor properties, enabling a down-scaling of the conductive paths to 150µm diameter and smaller. Furthermore, the described composite is biocompatible, non-magnetic, and chemically inert, which is vital for the application in active, implantable, medical devices. Beside the general fabrication route, we present the microstructural, functional, and mechanical properties of this newly developed class of dual composites. Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. Impact-Resistant Ceramic Coating

    NASA Technical Reports Server (NTRS)

    Wheeler, W. H.; Creedon, J. F.; Izu, Y. D.

    1986-01-01

    Refractory fibers more than double strength of coating. Impact strengths of ceramic coatings increase with increasing whisker content. Silicon carbide whiskers clearly produce largest increase, and improvement grows even more with high-temperature sintering. Coating also improves thermal and mechanical properties of electromagnetic components, mirrors, furnace linings, and ceramic parts of advanced internal-combustion engines.

  5. Fabrication of glass-ceramics containing spin-chain compound SrCuO{sub 2} and its high thermal conductivity

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

    Terakado, Nobuaki, E-mail: terakado@laser.apph.tohoku.ac.jp; Watanabe, Kouki; Kawamata, Takayuki

    2015-04-06

    High thermal conductivity materials are in great demand for heat-flow control and heat dissipation in electronic devices. In this study, we have produced a glass-ceramics that contains spin-chain compound SrCuO{sub 2} and have found that the glass-ceramics yields high thermal conductivity of ∼5 W K{sup −1} m{sup −1} even at room temperature. The glass-ceramics is fabricated through crystallization of inhomogeneous melt-quenched oxides made from SrCO{sub 3}, CuO, Li{sub 2}CO{sub 3}, Ga{sub 2}O{sub 3}, and Al{sub 2}O{sub 3}. Transmission electron microscopy and X-ray and electron diffraction reveal that SrCuO{sub 2} crystallites with a size of 100–200 nm are precipitated in the glass-ceramics. Themore » highness of the thermal conductivity is attributable to two sources: one is elongation of phonon mean free path due to the crystallization of the inhomogeneous structure or structural ordering. The other is emergence of the heat carriers, spinons, in the SrCuO{sub 2}. This highly thermal conductive glass-ceramics is expected to be utilized as base materials for heat-flow control devices.« less

  6. Femtosecond laser inscribed cladding waveguides in Nd:YAG ceramics: fabrication, fluorescence imaging and laser performance.

    PubMed

    Liu, Hongliang; Jia, Yuechen; Vázquez de Aldana, Javier Rodríguez; Jaque, Daniel; Chen, Feng

    2012-08-13

    We report on the fabrication of depressed cladding waveguide lasers in Nd:YAG (neodymium doped yttrium aluminum garnet, Nd:Y3Al5O12) ceramics microstructured by femtosecond laser pulses. Full control over the confined light spatial distribution is demonstrated by the fabrication of high contrast waveguides with hexagonal, circular and trapezoidal configurations. The confocal fluorescence measurements of the waveguides reveal that the original luminescence features of Nd3+ ions are well-preserved in the waveguide regions. Under optical pump at 808 nm, cladding waveguides showed continuous wave efficient laser oscillation. The maximum output power obtained at 1064.5 nm is ~181 mW with a slope efficiency as high as 44%, which suggests that the fabricated Nd:YAG ceramic waveguides are promising candidates for efficient integrated laser sources.

  7. Ceramic Technology Project semiannual progress report, April 1992--September 1992

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

    Johnson, D.R.

    1993-07-01

    This project was developed to meet the ceramic technology requirements of the DOE Office of Transportation Systems` automotive technology programs. Significant progress in fabricating ceramic components for DOE, NASA, and DOE advanced heat engine programs show that operation of ceramic parts in high-temperature engines is feasible; however, addition research is needed in materials and processing, design, and data base and life prediction before industry will have a sufficient technology base for producing reliable cost-effective ceramic engine components commercially. A 5-yr project plan was developed, with focus on structural ceramics for advanced gas turbine and diesel engines, ceramic bearings and attachments,more » and ceramic coatings for thermal barrier and wear applications in these engines.« less

  8. Advanced SiC/SiC Ceramic Composites For Gas-Turbine Engine Components

    NASA Technical Reports Server (NTRS)

    Yun, H. M.; DiCarlo, J. A.; Easler, T. E.

    2004-01-01

    NASA Glenn Research Center (GRC) is developing a variety of advanced SiC/SiC ceramic composite (ASC) systems that allow these materials to operate for hundreds of hours under stress in air at temperatures approaching 2700 F. These SiC/SiC composite systems are lightweight (approximately 30% metal density) and, in comparison to monolithic ceramics and carbon fiber-reinforced ceramic composites, are able to reliably retain their structural properties for long times under aggressive gas-turbine engine environments. The key for the ASC systems is related first to the NASA development of the Sylramic-iBN Sic fiber, which displays higher thermal stability than any other SiC- based ceramic fibers and possesses an in-situ grown BN surface layer for higher environmental durability. This fiber is simply derived from Sylramic Sic fiber type that is currently produced at ATK COI Ceramics (COIC). Further capability is then derived by using chemical vapor infiltration (CVI) and/or polymer infiltration and pyrolysis (PIP) to form a Sic-based matrix with high creep and rupture resistance as well as high thermal conductivity. The objectives of this study were (1) to optimize the constituents and processing parameters for a Sylramic-iBN fiber reinforced ceramic composite system in which the Sic-based matrix is formed at COIC almost entirely by PIP (full PIP approach), (2) to evaluate the properties of this system in comparison to other 2700 F Sylramic-iBN systems in which the matrix is formed by full CVI and CVI + PIP, and (3) to examine the pros and cons of the full PIP approach for fabricating hot-section engine components. A key goal is the development of a composite system with low porosity, thereby providing high modulus, high matrix cracking strength, high interlaminar strength, and high thermal conductivity, a major property requirement for engine components that will experience high thermal gradients during service. Other key composite property goals are demonstration at

  9. Intense 2.7 μm mid-infrared emission of Er{sup 3+} in oxyfluoride glass ceramic containing NaYF{sub 4} nanocrystals

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

    Liu, Yin; Liu, Xueyun; Wang, Weichao

    2016-04-15

    Highlights: • Transparent oxyfluoride glass-ceramics containing NaYF{sub 4}:Er{sup 3+} nanocrystals have been prepared. • Intense 2.7 μm emission of the glass-ceramics has been demonstrated. • Prolonged decay lifetimes of Er{sup 3+}:{sup 4}I{sub 11/2} and {sup 4}I{sub 13/2} levels have been achieved. - Abstract: Transparent oxyfluoride glass ceramics containing NaYF{sub 4}:Er{sup 3+} nanocrystals have been prepared by melt quenching and subsequent thermal treatment. X-ray diffraction and high-resolution transmission electron microscopy analysis confirmed the precipitation of NaYF{sub 4} nanocrystals in glass. Energy dispersive spectrometer results evidenced the preferential concentration of Er{sup 3+} ions in nanocrystals. Mid-infrared, upconversion, and near-infrared emissions were measuredmore » upon excitation with 980 nm laser diode and the luminescence mechanisms were discussed. Intense 2.7 μm emission originating from the Er{sup 3+}:{sup 4}I{sub 11/2} → {sup 4}I{sub 13/2} transition was achieved due to the incorporation of Er{sup 3+} ions into the precipitated low phonon energy fluoride nanocrystals. The results indicate that oxyfluoride glass ceramic containing NaYF{sub 4}:Er{sup 3+} nanocrystals is a promising candidate material for 2.7 μm laser.« less

  10. Thermal and Environmental Barrier Coatings for Advanced Turbine Engine Applications

    NASA Technical Reports Server (NTRS)

    Zhu, Dong-Ming; Miller, Robert A.

    2005-01-01

    Ceramic thermal and environmental barrier coatings (T/EBCs) will play a crucial role in advanced gas turbine engine systems because of their ability to significantly increase engine operating temperatures and reduce cooling requirements, thus help achieve engine low emission and high efficiency goals. Advanced T/EBCs are being developed for the low emission SiC/SiC ceramic matrix composite (CMC) combustor applications by extending the CMC liner and vane temperature capability to 1650 C (3000 F) in oxidizing and water vapor containing combustion environments. Low conductivity thermal barrier coatings (TBCs) are also being developed for metallic turbine airfoil and combustor applications, providing the component temperature capability up to 1650 C (3000 F). In this paper, ceramic coating development considerations and requirements for both the ceramic and metallic components will be described for engine high temperature and high-heat-flux applications. The underlying coating failure mechanisms and life prediction approaches will be discussed based on the simulated engine tests and fracture mechanics modeling results.

  11. Er3+-doped transparent glass ceramics containing micron-sized SrF2 crystals for 2.7 μm emissions

    PubMed Central

    Jiang, Yiguang; Fan, Jintai; Jiang, Benxue; Mao, Xiaojian; Tang, Junzhou; Xu, Yinsheng; Dai, Shixun; Zhang, Long

    2016-01-01

    Er3+-doped transparent glass ceramics containing micron-sized SrF2 crystals were obtained by direct liquid-phase sintering of a mixture of SrF2 powders and precursor glass powders at 820 °C for 15 min. The appearance and microstructural evolution of the SrF2 crystals in the resulting glass ceramics were investigated using X-ray diffraction, field-emission scanning electron microscopy and transmission microscopy. The SrF2 crystals are ~15 μm in size and are uniformly distributed throughout the fluorophosphate glass matrix. The glass ceramics achieve an average transmittance of 75% in the visible region and more than 85% in the near-IR region. The high transmittance of the glass ceramics results from matching the refractive index of the SrF2 with that of the precursor glass. Energy dispersive spectroscopy, photoluminescence spectra, and photoluminescence lifetimes verified the incorporation of Er3+ into the micron-sized SrF2 crystals. Intense 2.7 μm emissions due to the 4I11/2 → 4I13/2 transition were observed upon excitation at 980 nm using a laser diode. The maximum value of the emission cross section of Er3+ around 2.7 μm is more than 1.2 × 10−20 cm2, which indicates the potential of using transparent glass ceramics containing micron-sized SrF2 crystals for efficient 2.7 μm lasers and amplifiers. PMID:27430595

  12. Er(3+)-doped transparent glass ceramics containing micron-sized SrF2 crystals for 2.7 μm emissions.

    PubMed

    Jiang, Yiguang; Fan, Jintai; Jiang, Benxue; Mao, Xiaojian; Tang, Junzhou; Xu, Yinsheng; Dai, Shixun; Zhang, Long

    2016-07-19

    Er(3+)-doped transparent glass ceramics containing micron-sized SrF2 crystals were obtained by direct liquid-phase sintering of a mixture of SrF2 powders and precursor glass powders at 820 °C for 15 min. The appearance and microstructural evolution of the SrF2 crystals in the resulting glass ceramics were investigated using X-ray diffraction, field-emission scanning electron microscopy and transmission microscopy. The SrF2 crystals are ~15 μm in size and are uniformly distributed throughout the fluorophosphate glass matrix. The glass ceramics achieve an average transmittance of 75% in the visible region and more than 85% in the near-IR region. The high transmittance of the glass ceramics results from matching the refractive index of the SrF2 with that of the precursor glass. Energy dispersive spectroscopy, photoluminescence spectra, and photoluminescence lifetimes verified the incorporation of Er(3+) into the micron-sized SrF2 crystals. Intense 2.7 μm emissions due to the (4)I11/2 → (4)I13/2 transition were observed upon excitation at 980 nm using a laser diode. The maximum value of the emission cross section of Er(3+) around 2.7 μm is more than 1.2 × 10(-20) cm(2), which indicates the potential of using transparent glass ceramics containing micron-sized SrF2 crystals for efficient 2.7 μm lasers and amplifiers.

  13. Interdisciplinary research and development on the effects of the nature and properties of ceramic materials in the design of advanced structural components

    NASA Technical Reports Server (NTRS)

    1978-01-01

    An educational development and supportive research program on ceramic materials established to advance design methodology, improve materials, and develop engineers knowledgable in design with and use of high performance ceramic materials is described. Emphasis is on the structures and related materials problems in a ceramic turbine engine, but applications in coal gasification, solar conversion, and magnetohydrodynamic technologies are considered. Progress of various research projects in the areas of new materials, processing, characterization, and nondestructive testing is reported. Fracture toughness determination, extended X-ray absorption fine structure measurements, and grain boundary effects in beta-alumina are among the topics covered.

  14. Formation of Yttrium Oxysulfide Phosphor at Room Temperature

    NASA Astrophysics Data System (ADS)

    Shoji, Masahiko; Sakurai, Kenji

    2005-12-01

    Europium-doped yttrium oxysulfide (Y2O2S:Eu) phosphor was successfully synthesized at room temperature from yttrium oxide, europium oxide, and sulfur. The method employs high-energy ball milling to enable a substitution reaction between oxygen and sulfur, unlike conventional methods, such as heating in a sulfurizing atmosphere. It was found that the material is fluorescent through X-ray irradiation, and the luminescence spectra exhibit four peaks in the wavelength region from 500 to 800 nm.

  15. CO2 laser debonding of a ceramic bracket bonded with orthodontic adhesive containing thermal expansion microcapsules.

    PubMed

    Saito, Ayano; Namura, Yasuhiro; Isokawa, Keitaro; Shimizu, Noriyoshi

    2015-02-01

    We have been studying an easy bracket debonding method using heating of an orthodontic adhesive containing thermal expansion microcapsules. However, heating with a high-temperature heater brings obvious risks of burns around the oral cavity. Thus, we examined safer and more effective bracket debonding methods. The purpose of this in vitro study was to examine the reduction in debonding strength and the time taken using a bracket bonded with an orthodontic adhesive containing thermal expansion microcapsules and a CO2 laser as the heating method while maintaining safety. Ceramic brackets were bonded to bovine permanent mandibular incisors using bonding materials containing various microcapsule contents (0, 30, and 40 wt%), and the bond strengths were measured after laser irradiation for 4, 5, and 6 s and compared with nonlaser-treated groups. Subsequently, the temperature in the pulp chamber during laser irradiation was measured. After laser irradiation for 5 or 6 s, the bond strengths of the adhesive containing 40 wt% microcapsules were significantly decreased to ∼0.40 - 0.48-fold (4.6-5.5 MPa) compared with the nonlaser groups. The mean temperature rise of the pulp chamber was 4.3 °C with laser irradiation for 6 s, which was less than that required to induce pulp damage. Based on these results, we conclude that the combined use of a CO2 laser and an orthodontic adhesive containing thermal expansion microcapsules can be effective and safe for debonding ceramic brackets with less enamel damage or tooth pain.

  16. Probabilistic Evaluation of Advanced Ceramic Matrix Composite Structures

    NASA Technical Reports Server (NTRS)

    Abumeri, Galib H.; Chamis, Christos C.

    2003-01-01

    The objective of this report is to summarize the deterministic and probabilistic structural evaluation results of two structures made with advanced ceramic composites (CMC): internally pressurized tube and uniformly loaded flange. The deterministic structural evaluation includes stress, displacement, and buckling analyses. It is carried out using the finite element code MHOST, developed for the 3-D inelastic analysis of structures that are made with advanced materials. The probabilistic evaluation is performed using the integrated probabilistic assessment of composite structures computer code IPACS. The affects of uncertainties in primitive variables related to the material, fabrication process, and loadings on the material property and structural response behavior are quantified. The primitive variables considered are: thermo-mechanical properties of fiber and matrix, fiber and void volume ratios, use temperature, and pressure. The probabilistic structural analysis and probabilistic strength results are used by IPACS to perform reliability and risk evaluation of the two structures. The results will show that the sensitivity information obtained for the two composite structures from the computational simulation can be used to alter the design process to meet desired service requirements. In addition to detailed probabilistic analysis of the two structures, the following were performed specifically on the CMC tube: (1) predicted the failure load and the buckling load, (2) performed coupled non-deterministic multi-disciplinary structural analysis, and (3) demonstrated that probabilistic sensitivities can be used to select a reduced set of design variables for optimization.

  17. Electrolytic Deposition and Diffusion of Lithium onto Magnesium-9 Wt Pct Yttrium Bulk Alloy in Low-Temperature Molten Salt of Lithium Chloride and Potassium Chloride

    NASA Astrophysics Data System (ADS)

    Dong, Hanwu; Wu, Yaoming; Wang, Lidong; Wang, Limin

    2009-10-01

    The electrolytic deposition and diffusion of lithium onto bulk magnesium-9 wt pct yttrium alloy cathode in molten salt of 47 wt pct lithium chloride and 53 wt pct potassium chloride at 693 K were investigated. Results show that magnesium-yttrium-lithium ternary alloys are formed on the surface of the cathodes, and a penetration depth of 642 μm is acquired after 2 hours of electrolysis at the cathodic current density of 0.06 A·cm-2. The diffusion of lithium results in a great amount of precipitates in the lithium containing layer. These precipitates are the compound of Mg41Y5, which arrange along the grain boundaries and hinder the diffusion of lithium, and solid solution of yttrium in magnesium. The grain boundaries and the twins of the magnesium-9 wt pct yttrium substrate also have negative effects on the diffusion of lithium.

  18. Veneer Ceramic to Y-TZP Bonding: Comparison of Different Surface Treatments.

    PubMed

    Kirmali, Omer; Kapdan, Alper; Kustarci, Alper; Er, Kursat

    2016-06-01

    The purpose of this study was to evaluate the effects of various surface-treatment techniques for enhancing the bond strength between veneering ceramic and yttria-stabilized tetragonal zirconia polycrystals (Y-TZP). Pre-sintered Y-TZP specimens were divided into eight groups (n = 10) according to the surface-treatment technique used: (a) untreated (control); (b) air abrasion with aluminum oxide particles; (c) erbium, chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser irradiation at different energy intensities (1 to 6 W). All specimens were then sintered and veneered with veneering ceramic according to the manufacturer's instructions. The obtained zirconia-ceramic specimens were immersed in 37°C distilled water for 24 hours before a shear bond strength test using a universal testing device at a 1 mm/min crosshead speed. The average values were calculated. After debonding, the Y-TZP surfaces were examined under a stereomicroscope to determine their fracture pattern, and the surface topography was evaluated with scanning electron microscopy after surface treatments. The bond strength ranged from 13.24 to 20.54 MPa. All surface treatments increased the bond strength between the veneering ceramic and Y-TZP; however, the value for the 6 W irradiation group was significantly different from the values for other groups (p ˂ 0.05). The present study's findings showed that higher energy densities were needed for the laser irradiation to improve the bond strength between the veneering ceramic and zirconia. Y-TZP is commonly used as a core material in fixed restorations. The bond strength between zirconia and the veneering ceramic can be affected by various surface treatments. © 2015 by the American College of Prosthodontists.

  19. Influence of CAD/CAM systems and cement selection on marginal discrepancy of zirconia-based ceramic crowns.

    PubMed

    Martínez-Rus, Francisco; Suárez, María J; Rivera, Begoña; Pradíes, Guillermo

    2012-04-01

    To analyze the effect of ceramic manufacturing technique and luting cement selection on the marginal adaptation of zirconium oxide-based all-ceramic crowns. An extracted mandibular first premolar was prepared for a complete coverage restoration and subsequently duplicated 40 times in a liquid crystal polymer (LCP). All-ceramic crowns (n = 10) were fabricated on LCP models using the following systems: glass-infiltrated zirconia-toughened alumina (In-Ceram Zirconia) and yttrium cation-doped tetragonal zirconia polycrystals (In-Ceram YZ, Cercon, and Procera Zirconia). The restorations (n = 5) were cemented on their respective dies with glass-ionomer cement (Ketac Cem Aplicap) and resin cement (Panavia 21). The absolute marginal discrepancy of the crowns was measured before and after cementation by scanning electronic microscopy at 160 points along the circumferential margin. The data were analyzed using one-way ANOVA for repeated measures and for independent samples, Scheffé's multiple range post hoc test, and Student's t-test (alpha = 0.05). There were statistical differences in the mean marginal openings among the four all-ceramic systems before and after luting (P < 0.0001). The Procera restorations had the lowest pre- and post-cementation values (P < 0.0001). A significant increase in the marginal gap size caused by luting media occurred in all tested groups (P < 0.0001). Resin cement resulted in larger marginal discrepancies than glass-ionomer cement (P < 0.0001).

  20. Chemical precursors to non-oxide ceramics: Macro to nanoscale materials

    NASA Astrophysics Data System (ADS)

    Forsthoefel, Kersten M.

    Non-oxide ceramics exhibit a number of important properties that make them ideal for technologically important applications (thermal and chemical stability, high strength and hardness, wear-resistance, light weight, and a range of electronic and optical properties). Unfortunately, traditional methodologies to these types of materials are limited to fairly simple shapes and complex processed forms cannot be attained through these methods. The establishment of the polymeric precursor approach has allowed for the generation of advanced materials, such as refractory non-oxide ceramics, with controlled compositions, under moderate conditions, and in processed forms. The goal of the work described in this dissertation was both to develop new processible precursors to technologically important ceramics and to achieve the formation of advanced materials in processed forms. One aspect of this research exploited previously developed preceramic precursors to boron carbide, boron nitride and silicon carbide for the generation of a wide variety of advanced materials: (1) ultra-high temperature ceramic (UHTC) structural materials composed of hafnium boride and related composite materials, (2) the quaternary borocarbide superconductors, and (3) on the nanoscale, non-oxide ceramic nanotubules. The generation of the UHTC and the quaternary borocarbide materials was achieved through a method that employs a processible polymer/metal(s) dispersion followed by subsequent pyrolyses. In the case of the UHTC, hafnium oxide, hafnium, or hafnium boride powders were dispersed in a suitable precursor to afford hafnium borides or related composite materials (HfB2/HfC, HfB2/HfN, HfB2/SiC) in high yields and purities. The quaternary borocarbide superconducting materials were produced from pyrolyses of dispersions containing appropriate stoichiometric amounts of transition metal, lanthanide metal, and the polyhexenyldecaborane polymer. Both chemical vapor deposition (CVD) based routes employing a

  1. Enhancement of Superconductivity of Lanthanum and Yttrium Sesquicarbide

    DOEpatents

    Krupka, M. C.; Giorgi, A. L.; Krikorian, N. H.; Szklarz, E. G.

    1972-06-22

    A method of enhancing the superconductivity of body-centered cubic lanthanum and yttrium sesquicarbide through formation of the sesquicarbides from ternary alloys of novel composition (N/sub x/M/sub 1-x/)C/sub z/, where N is yttrium or lanthanum, M is thorium, any of the Group IV and VI transition metals, or gold, germanium or silicon, and z is approximately 1.2 to 1.6. These ternary sesquicarbides have superconducting transition temperatures as high as 17.0/sup 0/K.

  2. Enhancement of superconductivity of lanthanum and yttrium sesquicarbide

    DOEpatents

    Krupka, M.C.; Giorgi, A.L.; Krikorian, N.H.; Szklarz, E.G.

    1971-06-22

    A method of enhancing the superconductivity of body-centered cubic lanthanum and yttrium sesquicarbide through formation of the sesquicarbides from ternary alloys of novel composition (N/sub x/M/sub 1-x/)C/sub z/, where N is yttrium or lanthanum, M is thorium, any of the Group IV and VI transition metals, or gold, germanium or silicon, and z is approximately 1.2 to 1.6. These ternary sesquicarbides have superconducting transition temperatures as high as 17.0/sup 0/K.

  3. Advances in Understanding of Swift Heavy-Ion Tracks in Complex Ceramics

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

    Lang, Maik; Devanathan, Ram; Toulemonde, Marcel

    2015-02-01

    Tracks produced by swift heavy ions in ceramics are of interest for fundamental science as well as for applications covering different fields such as nanotechnology or fission-track dating of minerals. In the case of pyrochlores with general formula A2B2O7, the track structure and radiation sensitivity shows a clear dependence on the composition. Ion irradiated Gd2Zr2O7, e.g., retains its crystallinity while amorphous tracks are produced in Gd2Ti2O7. Tracks in Ti-containing compositions have a complex morphology consisting of an amorphous core surrounded by a shell of a disordered, defect-fluorite phase. The size of the amorphous core decreases with decreasing energy loss andmore » with increasing Zr content, while the shell thickness seems to be similar over a wide range of energy loss values. The large data set and the complex track structure has made pyrochlore an interesting model system for a general theoretical description of track formation including thermal spike calculations (providing the spatial and temporal evolution of temperature around the ion trajectory) and molecular dynamics (MD) simulations (describing the response of the atomic system).Recent MD advances consider the sudden temperature increase by inserting data from the thermal spike. The combination allows the reproduction of the core-shell track characteristic and sheds light on the early stages of track formation including recrystallization of the molten material produced by the thermal spike.« less

  4. Corrosion of Ceramic Materials

    NASA Technical Reports Server (NTRS)

    Opila, Elizabeth J.; Jacobson, Nathan S.

    1999-01-01

    Non-oxide ceramics are promising materials for a range of high temperature applications. Selected current and future applications are listed. In all such applications, the ceramics are exposed to high temperature gases. Therefore it is critical to understand the response of these materials to their environment. The variables to be considered here include both the type of ceramic and the environment to which it is exposed. Non-oxide ceramics include borides, nitrides, and carbides. Most high temperature corrosion environments contain oxygen and hence the emphasis of this chapter will be on oxidation processes.

  5. Electronic structure and electron-phonon interaction in hexagonal yttrium by density functional calculations

    NASA Astrophysics Data System (ADS)

    Singh, Prabhakar P.

    2007-03-01

    To understand the pressure-induced changes in the electronic structure and the electron-phonon interaction in yttrium, we have studied hexagonal-close-packed (hcp) yttrium, stable at ambient pressure, and double hexagonal-close-packed (dhcp) yttrium, stable up to around 44GPa , using density-functional-based methods. Our results show that as one goes from hcp yttrium to dhcp yttrium, there are (i) a substantial charge transfer from s→d with extensive modifications of the d band and a sizable reduction in the density of states at the Fermi energy, (ii) a substantial stiffening of phonon modes with the electron-phonon coupling covering the entire frequency range, and (iii) an increase in the electron-phonon coupling constant λ from 0.55 to 1.24, leading to a change in the superconducting transition temperature Tc from 0.3to15.3K for μ*=0.2 .

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

    PubMed Central

    Esfahani, Hamid; Ramakrishna, Seeram

    2017-01-01

    Ceramic nanofibers (NFs) have recently been developed for advanced applications due to their unique properties. In this article, we review developments in electrospun ceramic NFs with regard to their fabrication process, properties, and applications. We find that surface activity of electrospun ceramic NFs is improved by post pyrolysis, hydrothermal, and carbothermal processes. Also, when combined with another surface modification methods, electrospun ceramic NFs result in the advancement of properties and widening of the application domains. With the decrease in diameter and length of a fiber, many properties of fibrous materials are modified; characteristics of such ceramic NFs are different from their wide and long (bulk) counterparts. In this article, electrospun ceramic NFs are reviewed with an emphasis on their applications as catalysts, membranes, sensors, biomaterials, fuel cells, batteries, supercapacitors, energy harvesting systems, electric and magnetic parts, conductive wires, and wearable electronic textiles. Furthermore, properties of ceramic nanofibers, which enable the above applications, and techniques to characterize them are briefly outlined. PMID:29077074

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

    PubMed

    Esfahani, Hamid; Jose, Rajan; Ramakrishna, Seeram

    2017-10-27

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

  8. Method for preparing corrosion-resistant ceramic shapes

    DOEpatents

    Arons, R.M.; Dusek, J.T.

    1979-12-07

    Ceramic shapes having impermeable tungsten coatings can be used for containing highly corrosive molten alloys and salts. The shapes are prepared by coating damp green ceramic shapes containing a small amount of yttria with a tungsten coating slip which has been adjusted to match the shrinkage rate of the green ceramic and which will fire to a theoretical density of at least 80% to provide an impermeable coating.

  9. Method for preparing corrosion-resistant ceramic shapes

    DOEpatents

    Arons, Richard M.; Dusek, Joseph T.

    1983-09-13

    Ceramic shapes having impermeable tungsten coatings can be used for containing highly corrosive molten alloys and salts. The shapes are prepared by coating damp green ceramic shapes containing a small amount of yttria with a tungsten coating slip which has been adjusted to match the shrinkage rate of the green ceramic and which will fire to a theoretical density of at least 80% to provide a impermeable coating.

  10. Alkali metal yttrium neo-pentoxide double alkoxide precursors to alkali metal yttrium oxide nanomaterials

    DOE PAGES

    Boyle, Timothy J.; Neville, Michael L.; Sears, Jeremiah Matthew; ...

    2016-03-15

    In this study, a series of alkali metal yttrium neo-pentoxide ([AY(ONep) 4]) compounds were developed as precursors to alkali yttrium oxide (AYO 2) nanomaterials. The reaction of yttrium amide ([Y(NR 2) 3] where R=Si(CH 3) 3) with four equivalents of H-ONep followed by addition of [A(NR 2)] (A=Li, Na, K) or A o (A o=Rb, Cs) led to the formation of a complex series of A nY(ONep) 3+n species, crystallographically identified as [Y 2Li 3(μ 3-ONep)(μ 3-HONep)(μ-ONep) 5(ONep) 3(HONep) 2] (1), [YNa 2(μ 3-ONep) 4(ONep)] 2 (2), {[Y 2K 3(μ 3-ONep) 3(μ-ONep) 4(ONep) 2(ηξ-tol) 2][Y 4K 2(μ 4-O)(μ 3-ONep) 8(ONep)more » 4]•η x-tol]} (3), [Y 4K 2(μ 4-O)(μ 3-ONep) 8(ONep) 4] (3a), [Y 2Rb 3(μ 4-ONep) 3(μ-ONep) 6] (4), and [Y 2Cs 4(μ 6-O)(μ 3-ONep) 6(μ 3-HONep) 2(ONep) 2(η x-tol) 4]•tol (5). Compounds 1–5 were investigated as single source precursors to AYOx nanomaterials following solvothermal routes (pyridine, 185 °C for 24h). The final products after thermal processing were found by powder X-ray diffraction experiments to be Y 2O 3 with variable sized particles based on transmission electron diffraction. Energy dispersive X-ray spectroscopy studies indicated that the heavier alkali metal species were present in the isolated nanomaterials.« less

  11. Maintaining High Strength in Mg-LPSO Alloys with Low Yttrium Content Using Severe Plastic Deformation.

    PubMed

    Garces, Gerardo; Cabeza, Sandra; Barea, Rafael; Pérez, Pablo; Adeva, Paloma

    2018-05-05

    Alternative processing routes such as powder metallurgy, the extrusion of recycled chips, or equal channel angular pressing (ECAP) have been considered for effective methods of maintaining the high mechanical strength of Mg-Y-Zn alloys containing long-period stacking ordered structures with respect to the alloy processed by the conventional extrusion of as-cast ingots with the advantage of minimizing the yttrium content. A yield stress similar to that found for extruded Mg 97 Y₂Zn₁ alloy can be attained with only half of the usual yttrium and zinc additions thanks to the grain refinement induced by ECAP processing. The properties of Mg 98.5 Y₁Zn 0.5 subjected to ECAP are maintained up to 200 °C, but superplastic behavior is found above this temperature when the alloy is processed through a powder metallurgy route.

  12. Design and evaluation of experimental ceramic automobile thermal reactors

    NASA Technical Reports Server (NTRS)

    Stone, P. L.; Blankenship, C. P.

    1974-01-01

    The results obtained in an exploratory evaluation of ceramics for automobile thermal reactors are summarized. Candidate ceramic materials were evaluated in several reactor designs by using both engine-dynamometer and vehicle road tests. Silicon carbide contained in a corrugated-metal support structure exhibited the best performance, lasting 1100 hr in engine-dynamometer tests and more than 38,600 km (24000 miles) in vehicle road tests. Although reactors containing glass-ceramic components did not perform as well as those containing silicon carbide, the glass-ceramics still offer good potential for reactor use with improved reactor designs.

  13. Influence of substituting B2O3 for CaF2 on the bonding behaviour to bone of glass-ceramics containing apatite and wollastonite.

    PubMed

    Kitsugi, T; Yamamuro, T; Nakamura, T; Yoshii, S; Kokubo, T; Takagi, M; Shibuya, T

    1992-01-01

    Glass-ceramics containing crystalline oxy-fluoroapatite (Ca10(PO4)6(O,F2)) and wollastonite (CaSiO3) (designated AWGC) are reported to have a fairly high mechanical strength as well as the capability of forming a chemical bond with bone tissue. The chemical composition is MgO 4.6, CaO 44.9, SiO2 34.2, P2O5 16.3, and CaF2 0.5 in weight ratio. In this study the influence of substituting B2O3 for CaF2 on the bonding behaviour of glass-ceramics containing apatite and wollastonite to bone tissue was investigated. Two kinds of glass-ceramics containing apatite and wollastonite were prepared. CaF2 0.5 was replaced with B2O3 at 0.5 and 2.0 in weight ratio (designated AWGC-0.5B and AWGC-2.0B). Rectangular ceramic plates (15 x 10 x 2 mm, abraded with No. 2000 alumina powder) were implanted into a rabbit tibia. The failure load, when an implant detached from the bone, or the bone itself broke, was measured. The failure load of AWGC-0.5B was 8.00 +/- 1.82 kg at 10 weeks after implantation and 8.16 +/- 1.36 kg at 25 weeks after implantation. The failure load of AWGC-2B was 8.08 +/- 1.70 kg at 10 weeks after implantation and 9.92 +/- 2.46 kg at 25 weeks after implantation. None of the loads for the two kinds of glass-ceramics decreased as time passed. Giemsa surface staining and contact microradiography revealed direct bonding between glass-ceramics and bone. SEM-EPMA showed a calcium-phosphorus rich layer (reaction zone) at the interface of ceramics and bone tissue. The thickness of the reaction zone was 10 to -15 microns and did not increase as time passed.(ABSTRACT TRUNCATED AT 250 WORDS)

  14. Structural characterisation of advanced optical materials

    NASA Astrophysics Data System (ADS)

    Krsmanovic, Radenka

    The rare earth systems discussed in this thesis belong to a class of new, advanced optical materials. Two different nanostuctured materials are studied: nanocrystalline oxide phosphors and glass ceramics containing luminescent nanocrystals. In both cases, the optical activity is based on the luminescence properties of rare earth dopants incorporated into the crystal structure of the insulator nanocrystals themselves. The structure, morphology and composition of these luminescent composite materials are investigated and used to demonstrate the benefits as well as the drawbacks of the synthesis and the processing techniques used, aiming to their improvement for possible industrial production. An investigation of the microstructure was done by XRD, TEM and HREM, while EDX, EELS and EFTEM spectroscopy techniques were used for the chemical identification. Our research clearly demonstrated that these techniques can be successfully applied, and in combination with optical spectroscopy can provide the complete characterization of nanostructured luminescent materials. Three different oxide phosphors in the form of nanocrystalline powders are obtained with the solution combustion technique: yttrium aluminum garnet (YAG), gadolinium gallium garnet (GGG) and scandium oxide, Sc2O 3. We found out that GGG and Sc2O3 samples have "perfect" nanocrystals, without defects or amorphous surface layer, and with uniform distribution of rare earth activators. Good crystal quality results in a long-lived phosphor and much stronger emission, which makes them promising candidate for display industry. Moreover, these luminescent nanocrystals are biocompatible and when functionalized with some molecules or biocompatible polymers can be used for bio-applications like "in vivo" markers in cell biology. For luminescence glass ceramics samples the ternary glass system Li 2O-Al2O3-SiO2 (LAS) is used as host matrix, and ZrO2 as nucleating agent for luminescent ions introduced as Eu2O3 or Er2O3. We

  15. Light-weight ceramic insulation

    NASA Technical Reports Server (NTRS)

    Hsu, Ming-Ta S. (Inventor); Chen, Timothy S. (Inventor)

    2002-01-01

    Ultra-high temperature, light-weight, ceramic insulation such as ceramic tile is obtained by pyrolyzing a siloxane gel derived from the reaction of at least one organo dialkoxy silane and at least one tetralkoxy silane in an acid or base liquid medium. The reaction mixture of the tetra- and dialkoxy silanes may contain also an effective amount of a mono- or trialkoxy silane to obtain the siloxane gel. The siloxane gel is dried at ambient pressures to form a siloxane ceramic precursor without significant shrinkage. The siloxane ceramic precursor is subsequently pyrolyzed, in an inert atmosphere, to form the black ceramic insulation comprising atoms of silicon, carbon and oxygen. The ceramic insulation, can be characterized as a porous, uniform ceramic tile resistant to oxidation at temperatures ranging as high as 1700.degree. C. and is particularly useful as lightweight tiles for spacecraft and other high-temperature insulation applications.

  16. Ablation Resistant Zirconium and Hafnium Ceramics

    NASA Technical Reports Server (NTRS)

    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.

  17. Survival Predictions of Ceramic Crowns Using Statistical Fracture Mechanics

    PubMed Central

    Nasrin, S.; Katsube, N.; Seghi, R.R.; Rokhlin, S.I.

    2017-01-01

    This work establishes a survival probability methodology for interface-initiated fatigue failures of monolithic ceramic crowns under simulated masticatory loading. A complete 3-dimensional (3D) finite element analysis model of a minimally reduced molar crown was developed using commercially available hardware and software. Estimates of material surface flaw distributions and fatigue parameters for 3 reinforced glass-ceramics (fluormica [FM], leucite [LR], and lithium disilicate [LD]) and a dense sintered yttrium-stabilized zirconia (YZ) were obtained from the literature and incorporated into the model. Utilizing the proposed fracture mechanics–based model, crown survival probability as a function of loading cycles was obtained from simulations performed on the 4 ceramic materials utilizing identical crown geometries and loading conditions. The weaker ceramic materials (FM and LR) resulted in lower survival rates than the more recently developed higher-strength ceramic materials (LD and YZ). The simulated 10-y survival rate of crowns fabricated from YZ was only slightly better than those fabricated from LD. In addition, 2 of the model crown systems (FM and LD) were expanded to determine regional-dependent failure probabilities. This analysis predicted that the LD-based crowns were more likely to fail from fractures initiating from margin areas, whereas the FM-based crowns showed a slightly higher probability of failure from fractures initiating from the occlusal table below the contact areas. These 2 predicted fracture initiation locations have some agreement with reported fractographic analyses of failed crowns. In this model, we considered the maximum tensile stress tangential to the interfacial surface, as opposed to the more universally reported maximum principal stress, because it more directly impacts crack propagation. While the accuracy of these predictions needs to be experimentally verified, the model can provide a fundamental understanding of the

  18. Modification of the rheological properties of screen printing ceramic paints containing gold

    NASA Astrophysics Data System (ADS)

    Izak, P.; Mastalska-Poplawska, J.; Lis, J.; Stempkowska, A.

    2017-01-01

    This work presents the results of modification of rheological properties of screen printing paints containing gold. 15 wt% glossy gold paste and 15 wt% glossy liquid gold were used as modifiers containing gold. The study showed that the gold paint for screen printing can be obtained by evaporation of the 15 wt% liquid gold and the golden luster. The compaction process of liquid gold by evaporation is slow and easy to perform in industrial conditions. The second way to adapt the 15 wt% gold ceramic paint for screen printing application depended on adding the aniseed oil and the pine oil. The course of the flow curve of the gold paste without modification indicates that it is shear thinning and shows the desired effect of thixotropy, and even anti-thixotropy, at low shear rates (<50-1 s-1). The introduction of the essential oils eliminates this phenomenon and the paste converts itself from the non-rheostable to the rheostable liquid.

  19. Development of advanced lightweight containment systems

    NASA Technical Reports Server (NTRS)

    Stotler, C.

    1981-01-01

    Parametric type data were obtained on advanced lightweight containment systems. These data were used to generate design methods and procedures necessary for the successful development of such systems. The methods were then demonstrated through the design of a lightweight containment system for a CF6 size engine. The containment concept evaluated consisted basically of a lightweight structural sandwich shell wrapped with dry Kevlar cloth. The initial testing was directed towards the determination of the amount of Kevlar required to result in threshold containment for a specific set of test conditions. A relationship was then developed between the thickness required and the energy of the released blade so that the data could be used to design for conditions other than those tested.

  20. Optimization Recovery of Yttrium Oxide in Precipitation, Extraction, and Stripping Process

    NASA Astrophysics Data System (ADS)

    Perwira, N. I.; Basuki, K. T.; Biyantoro, D.; Effendy, N.

    2018-04-01

    Yttrium oxide can be used as a dopant control rod of nuclear reactors in YSH material and superconductors. Yttrium oxide is obtained in the Xenotime mineral derived from byproduct of tin mining PT Timah Bangka which contain rare earth elements (REE) dominant Y, Dy, and Gd whose content respectively about 29.53%, 7.76%, and 2.58%. Both usage in the field of nuclear and non-nuclear science and technology is need to pure from the impurities. The presence of impurities in the yttrium oxide may affect the characteristic of the material and the efficiency of its use. Thus it needs to be separated by precipitation and extraction-stripping and calcination in the making of the oxide. However, to obtain higher levels of Yttrium oxide, it is necessary to determine the optimum conditions for its separation. The purpose of this research was to determine the optimum pH of precipitation, determine acid media and concentration optimum in extraction and stripping process and determine the efficiency of the separation of Y from REE concentrate. This research was conducted with pH variation in the precipitation process that pHs were 4 - 8, the difference of acid media for the extraction process, i.e., HNO3, HCl and H2SO4 with each concentration of 0,5 M; 1 M; 1,5 M; and 2 M and for stripping process were HNO3, HCl, and H2SO4 with each concentration of 1 M; 2M; and 3 M. Based on the result, the optimum pH of precipitation process was 6,5, the optimumacid media was HNO3 0,5 M, and for stripping process media was HNO3 3 M. The efficiency of precipitation process at pH 6,5 was 69,53 %, extraction process was 96.39% and stripping process was 4,50%. The separation process from precipitation to extraction had increased the purity and the highest efficiency recovery of Y was in the extraction process and obtained Y2O3 purer compared to the feed with the Y2O3 content of 92.87%.

  1. Exploratory evaluation of ceramics for automobile thermal reactors

    NASA Technical Reports Server (NTRS)

    Stone, P. L.; Blankenship, C. P.

    1972-01-01

    An exploratory evaluation of ceramics for automobile thermal reactors was conducted. Potential ceramic materials were evaluated in several reactor designs using both engine dynamometer and vehicle road tests. Silicon carbide contained in a corrugated metal support structure exhibited the best performance lasting over 800 hours in engine dynamometer tests and over 15,000 miles (24,200 km) of vehicle road tests. Reactors containing glass-ceramic components did not perform as well as silicon carbide. But the glass-ceramics still offer good potential for reactor use. The results of this study are considered to be a reasonable demonstration of the potential use of ceramics in thermal reactors.

  2. Yttrium and rare earth stabilized fast reactor metal fuel

    DOEpatents

    Guon, Jerold; Grantham, LeRoy F.; Specht, Eugene R.

    1992-01-01

    To increase the operating temperature of a reactor, the melting point and mechanical properties of the fuel must be increased. For an actinide-rich fuel, yttrium, lanthanum and/or rare earth elements can be added, as stabilizers, to uranium and plutonium and/or a mixture of other actinides to raise the melting point of the fuel and improve its mechanical properties. Since only about 1% of the actinide fuel may be yttrium, lanthanum, or a rare earth element, the neutron penalty is low, the reactor core size can be reduced, the fuel can be burned efficiently, reprocessing requirements are reduced, and the nuclear waste disposal volumes reduced. A further advantage occurs when yttrium, lanthanum, and/or other rare earth elements are exposed to radiation in a reactor, they produce only short half life radioisotopes, which reduce nuclear waste disposal problems through much shorter assured-isolation requirements.

  3. Current Scenario of Ceramic Engineering Education in India

    ERIC Educational Resources Information Center

    Srivastava, Aaditya Ranjan; Bajpai, Shrish; Khare, Sushant

    2018-01-01

    Historical overview of ceramic development has been provided in the paper. It has been stated that the trail of ceramics has been rooted in Indus valley civilization. Advancement of materials leads to afflux of development in the fields of science and technology. Present paper deals with the realm of Ceramic Engineering, mainly focuses on…

  4. Elevated Temperature Properties of Titanium Carbide Base Ceramals Containing Nickel or Iron

    NASA Technical Reports Server (NTRS)

    Cooper, A L; Colteryahn, L E

    1951-01-01

    Elevated-temperature properties of titanium carbide base ceramals containing nickel or iron were determined in oxidation, modulus of rupture, tensile strength, and thermal-shock resistance. These materials followed the general growth law and exhibited two stages in oxidation. The following tensile strengths were found at 2000 degrees F: 13.3 weight percent nickel, 16, 150 pounds per square inch; 11.8 weight percent iron, 12,500 pounds per square inch; unalloyed titanium carbide, 16,450 pounds per square inch. Nickel or iron additions to titanium carbide improved the thermal-shock resistance, nickel more. The path of fracture in tensile and thermal-shock specimens was found to progress approximately 50 percent intergranularly and 50 percent transgranularly.

  5. Ceramic and non-ceramic hydroxyapatite as a bone graft material: a brief review.

    PubMed

    Dutta, S R; Passi, D; Singh, P; Bhuibhar, A

    2015-03-01

    Treatment of dental, craniofacial and orthopedic defects with bone graft substitutes has shown promising result achieving almost complete bone regeneration depending on product resorption similar to human bone's physicochemical and crystallographic characteristics. Among these, non-ceramic and ceramic hydroxyapatite being the main inorganic salt of bone is the most studied calcium phosphate material in clinical practices ever since 1970s and non-ceramic since 1985. Its "chemical similarity" with the mineralized phase of biologic bone makes it unique. Hydroxyapatite as an excellent carrier of osteoinductive growth factors and osteogenic cell populations is also useful as drug delivery vehicle regardless of its density. Porous ceramic and non-ceramic hydroxyapatite is osteoconductive, biocompatible and very inert. The need for bone graft material keeps on increasing with increased age of the population and the increased conditions of trauma. Recent advances in genetic engineering and doping techniques have made it possible to use non-ceramic hydroxyapatite in larger non-ceramic crystals and cluster forms as a successful bone graft substitute to treat various types of bone defects. In this paper we have mentioned some recently studied properties of hydroxyapatite and its various uses through a brief review of the literatures available to date.

  6. The effect of CO2 and Nd:YAP lasers on CAD/CAM Ceramics: SEM, EDS and thermal studies.

    PubMed

    El Gamal, Ahmed; Fornaini, Carlo; Rocca, Jean Paul; Muhammad, Omid H; Medioni, Etienne; Cucinotta, Annamaria; Brulat-Bouchard, Nathalie

    2016-03-31

    The objective of this study was to investigate the interaction of infrared laser light on Computer Aided Design and Computer Aided Manufacturing (CAD/CAM) ceramic surfaces. Sixty CAD/CAM ceramic discs were prepared and divided into two different groups: lithiumdisilicate ceramic (IPSe.maxCADs) and Zirconia ceramic (IPSe.maxZirCADs). The laser irradiation was performed on graphite and non-graphite surfaces with a Carbon Dioxide laser at 5W and 10W power in continuous mode (CW mode) and with Neodymium Yttrium Aluminum Perovskite (Nd:YAP) laser at 10W. Surface textures and compositions were examined using Scanning Electron Microscopy (SEM), and Energy Dispersive Spectroscopy (EDS). Thermal elevation was measured by thermocouple during laser irradiation. The SEM observation showed a rough surface plus cracks and fissures on CO2 10W samples and melting areas in Nd:YAP samples; moreover, with CO2 5W smooth and shallow surfaces were observed. EDS analysis revealed that laser irradiation does not result in modifications of the chemical composition even if minor changes in the atomic mass percentage of the components were registered. Thermocouple showed several thermal changes during laser irradiation. CO2 and Nd:YAP lasers modify CAD/CAM ceramic surface without chemical composition modifications.

  7. The effect of CO2 and Nd:YAP lasers on CAD/CAM Ceramics: SEM, EDS and thermal studies

    PubMed Central

    Fornaini, Carlo; Rocca, Jean Paul; Muhammad, Omid H; Medioni, Etienne; Cucinotta, Annamaria; Brulat-Bouchard, Nathalie

    2016-01-01

    Background and aims: The objective of this study was to investigate the interaction of infrared laser light on Computer Aided Design and Computer Aided Manufacturing (CAD/CAM) ceramic surfaces. Material and Methods: Sixty CAD/CAM ceramic discs were prepared and divided into two different groups: lithiumdisilicate ceramic (IPSe.maxCADs) and Zirconia ceramic (IPSe.maxZirCADs). The laser irradiation was performed on graphite and non-graphite surfaces with a Carbon Dioxide laser at 5W and 10W power in continuous mode (CW mode) and with Neodymium Yttrium Aluminum Perovskite (Nd:YAP) laser at 10W. Surface textures and compositions were examined using Scanning Electron Microscopy (SEM), and Energy Dispersive Spectroscopy (EDS). Thermal elevation was measured by thermocouple during laser irradiation. Results: The SEM observation showed a rough surface plus cracks and fissures on CO2 10W samples and melting areas in Nd:YAP samples; moreover, with CO2 5W smooth and shallow surfaces were observed. EDS analysis revealed that laser irradiation does not result in modifications of the chemical composition even if minor changes in the atomic mass percentage of the components were registered. Thermocouple showed several thermal changes during laser irradiation. Conclusion: CO2 and Nd:YAP lasers modify CAD/CAM ceramic surface without chemical composition modifications. PMID:27141152

  8. Effect of Er:YAG laser irradiation on bonding property of zirconia ceramics to resin cement.

    PubMed

    Lin, Yihua; Song, Xiaomeng; Chen, Yaming; Zhu, Qingping; Zhang, Wei

    2013-12-01

    This study aimed to investigate whether or not an erbium: yttrium-aluminum-garnet (Er:YAG) laser could improve the bonding property of zirconia ceramics to resin cement. Surface treatments can improve the bonding properties of dental ceramics. However, little is known about the effect of Er:YAG laser irradiated on zirconia ceramics. Specimens of zirconia ceramic pieces were made, and randomly divided into 11 groups according to surface treatments, including one control group (no treatment), one air abrasion group, and nine Er:YAG laser groups. The laser groups were subdivided by applying different energy intensities (100, 200, or 300 mJ) and irradiation times (5, 10, or 15 sec). After surface treatments, ceramic pieces had their surface morphology observed, and their surface roughness was measured. All specimens were bonded to resin cement. Shear bond strength was measured after the bonded specimens were stored in water for 24 h, and additionally aged by thermocycling. Statistical analyses were performed using one way analysis of variance (ANOVA) and Tukey's test for shear bond strength, and Dunnett's t test for surface roughness, with α=0.05. Er:YAG laser irradiation changed the morphological characteristics of zirconia ceramics. Higher energy intensities (200, 300 mJ) could roughen the ceramics, but also caused surface cracks. There were no significant differences in the bond strength between the control group and the laser groups treated with different energy intensities or irradiation times. Air abrasion with alumina particles induced highest surface roughness and shear bond strength. Er:YAG laser irradiation cannot improve the bonding property of zirconia ceramics to resin cement. Enhancing irradiation intensities and extending irradiation time have no benefit on the bond of the ceramics, and might cause material defect.

  9. Ceramic components for the AGT 100 engine

    NASA Technical Reports Server (NTRS)

    Helms, H. E.; Heitman, P. W.

    1983-01-01

    Historically, automotive gas turbines have not been able to meet requirements of the marketplace with respect to cost, performance, and reliability. However, the development of appropriate ceramic materials has overcome problems related to a need for expensive superalloy components and to limitations regarding the operating temperature. An automotive gas turbine utilizing ceramic components has been developed by a U.S. automobile manufacturer. A 100-horsepower, two-shaft, regenerative engine geometry was selected because it is compatible with manual, automatic, and continuously variable transmissions. Attention is given to the ceramic components, the ceramic gasifier turbine rotor development, the ceramic gasifier scroll, ceramic component testing, and the use of advanced nondestructive techniques for the evaluation of the engine components.

  10. Melt Infiltrated Ceramic Matrix Composites for Shrouds and Combustor Liners of Advanced Industrial Gas Turbines

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

    Gregory Corman; Krishan Luthra; Jill Jonkowski

    2011-01-07

    This report covers work performed under the Advanced Materials for Advanced Industrial Gas Turbines (AMAIGT) program by GE Global Research and its collaborators from 2000 through 2010. A first stage shroud for a 7FA-class gas turbine engine utilizing HiPerComp{reg_sign}* ceramic matrix composite (CMC) material was developed. The design, fabrication, rig testing and engine testing of this shroud system are described. Through two field engine tests, the latter of which is still in progress at a Jacksonville Electric Authority generating station, the robustness of the CMC material and the shroud system in general were demonstrated, with shrouds having accumulated nearly 7,000more » hours of field engine testing at the conclusion of the program. During the latter test the engine performance benefits from utilizing CMC shrouds were verified. Similar development of a CMC combustor liner design for a 7FA-class engine is also described. The feasibility of using the HiPerComp{reg_sign} CMC material for combustor liner applications was demonstrated in a Solar Turbines Ceramic Stationary Gas Turbine (CSGT) engine test where the liner performed without incident for 12,822 hours. The deposition processes for applying environmental barrier coatings to the CMC components were also developed, and the performance of the coatings in the rig and engine tests is described.« less

  11. Microstructurally tailored ceramics for advanced energy applications by thermoreversible gelcasting

    NASA Astrophysics Data System (ADS)

    Shanti, Noah Omar

    Thermoreversible gelcasting (TRG) is an advantageous technique for rapidly producing bulk, net-shape ceramics and laminates. In this method, ceramic powder is suspended in warm acrylate triblock copolymer/alcohol solutions that reversibly gel upon cooling by the formation of endblock aggregates, to produce slurries which are cast into molds. Gel properties can be tailored by controlling the endblock and midblock lengths of the copolymer network-former and selecting an appropriate alcohol solvent. This research focuses on expanding and improving TRG techniques, focusing specifically on advanced energy applications including the solid oxide fuel cell (SOFC). Rapid drying of filled gels can lead to warping and cracking caused by high differential capillary stresses. A new drying technique using concentrated, alcohol-based solutions as liquid desiccants (LDs) to greatly reduce warping is introduced. The optimal LD is a poly(tert-butyl acrylate)/isopropyl alcohol solution with 5 mol% tert-butyl acrylate units. Alcohol emissions during drying are completely eliminated by combining initial drying in an LD with final stage drying in a vacuum oven having an in-line solvent trap. Porous ceramics are important structures for many applications, including SOFCs. Pore network geometries are tailored by the addition of fugitive fillers to TRG slurries. Uniform spherical, bimodal spherical and uniform fibrous fillers are used. Three-dimensional pore structures are visualized by X-ray computed tomography, allowing for direct measurements of physical parameters such as concentration and morphology as well as transport properties such as tortuosity. Tortuosity values as low as 1.52 are achieved when 60 vol% of solids are uniform spherical filler. Functionally graded laminates with layers ranging from 10 mum to > 1 mm thick are produced with a new technique that combines TRG with tape casting. Gels used for bulk casting are not suitable for use with tape casting, and appropriate base

  12. Accelerated Testing Methodology in Constant Stress-Rate Testing for Advanced Structural Ceramics: A Preloading Technique

    NASA Technical Reports Server (NTRS)

    Choi, Sung R.; Gyekenyesi, John P.; Huebert, Dean; Bartlett, Allen; Choi, Han-Ho

    2001-01-01

    Preloading technique was used as a means of an accelerated testing methodology in constant stress-rate ('dynamic fatigue') testing for two different brittle materials. The theory developed previously for fatigue strength as a function of preload was further verified through extensive constant stress-rate testing for glass-ceramic and CRT glass in room temperature distilled water. The preloading technique was also used in this study to identify the prevailing failure mechanisms at elevated temperatures, particularly at lower test rate in which a series of mechanisms would be associated simultaneously with material failure, resulting in significant strength increase or decrease. Two different advanced ceramics including SiC whisker-reinforced composite silicon nitride and 96 wt% alumina were used at elevated temperatures. It was found that the preloading technique can be used as an additional tool to pinpoint the dominant failure mechanism that is associated with such a phenomenon of considerable strength increase or decrease.

  13. Accelerated Testing Methodology in Constant Stress-Rate Testing for Advanced Structural Ceramics: A Preloading Technique

    NASA Technical Reports Server (NTRS)

    Choi, Sung R.; Gyekenyesi, John P.; Huebert, Dean; Bartlett, Allen; Choi, Han-Ho

    2001-01-01

    Preloading technique was used as a means of an accelerated testing methodology in constant stress-rate (dynamic fatigue) testing for two different brittle materials. The theory developed previously for fatigue strength as a function of preload was further verified through extensive constant stress-rate testing for glass-ceramic and CRT glass in room temperature distilled water. The preloading technique was also used in this study to identify the prevailing failure mechanisms at elevated temperatures, particularly at lower test rates in which a series of mechanisms would be associated simultaneously with material failure, resulting in significant strength increase or decrease. Two different advanced ceramics including SiC whisker-reinforced composite silicon nitride and 96 wt% alumina were used at elevated temperatures. It was found that the preloading technique can be used as an additional tool to pinpoint the dominant failure mechanism that is associated with such a phenomenon of considerable strength increase or decrease.

  14. [Preparation of porous ceramics based on waste ceramics and its Ni2+ adsorption characteristics].

    PubMed

    Zhang, Yong-Li; Wang, Cheng-Zhi; Shi, Ce; Shang, Ling-Ling; Ma, Rui; Dong, Wan-Li

    2013-07-01

    The preparation conditions of porous ceramics were determined by SEM, XRD and FT-IR characterizations as well as the nickel removal ability of porous ceramics to be: the mass fraction w of sesbania powder doped was 4%, and the calcination temperature was 800 degrees C. SEM and pore structure characterization illustrated that calcination caused changes in the structure and morphology of waste ceramics. With the increase of calcination temperature, the specific surface area and pore volume decreased, while the aperture increased. EDS analyses showed that the main elements of both the original waste porcelain powder and the porous ceramics were Si, Al and O. The SEM, XRD and FT-IR characterization of porous ceramics illustrated that the structure of porous ceramics was stable before and after adsorption. The series of experiments of Ni2+ adsorption using these porous ceramics showed that when the dosage of porous ceramics was 10 g x L(-1), the adsorption time was 60 min, the pH value was 6.32, and the concentration of nickel-containing wastewater was below 100 mg x L(-1), the Ni2+ removal of wastewater reached 89.7%. Besides, the porous ceramics showed higher removal efficiency on nickel in the wastewater. The Ni(2+)-containing wastewater was processed by the porous ceramics prepared, and the adsorption dynamics and adsorption isotherms of Ni2+ in wastewater by porous ceramics were investigated. The research results showed that the Ni2+ adsorption process of porous ceramics was in accordance with the quasi second-order kinetic model (R2 = 0.999 9), with Q(e) of 9.09 mg x g(-1). The adsorption process can be described by the Freundlich equation and Langmuir equation, and when the temperature increased from 20 degrees C to 40 degrees C, the maximum adsorption capacity Q(m) increased from 14.49 mg x g(-1) to 15.38 mg x g(-1).

  15. Structural ceramics containing electric arc furnace dust.

    PubMed

    Stathopoulos, V N; Papandreou, A; Kanellopoulou, D; Stournaras, C J

    2013-11-15

    In the present work the stabilization of electric arc furnace dust EAFD waste in structural clay ceramics was investigated. EAFD was collected over eleven production days. The collected waste was characterized for its chemical composition by Flame Atomic Absorption Spectroscopy. By powder XRD the crystal structure was studied while the fineness of the material was determined by a laser particle size analyzer. The environmental characterization was carried out by testing the dust according to EN12457 standard. Zn, Pb and Cd were leaching from the sample in significant amounts. The objective of this study is to investigate the stabilization properties of EAFD/clay ceramic structures and the potential of EAFD utilization into structural ceramics production (blocks). Mixtures of clay with 2.5% and 5% EAFD content were studied by TG/DTA, XRD, SEM, EN12457 standard leaching and mechanical properties as a function of firing temperature at 850, 900 and 950 °C. All laboratory facilities maintained 20 ± 1 °C. Consequently, a pilot-scale experiment was conducted with an addition of 2.5% and 5% EAFD to the extrusion mixture for the production of blocks. During blocks manufacturing, the firing step reached 950 °C in a tunnel kiln. Laboratory heating/cooling gradients were similar to pilot scale production firing. The as produced blocks were then subjected to quality control tests, i.e. dimensions according to EN772-17, water absorbance according to EN772-6, and compressive strength according to EN772-1 standard, in laboratory facilities certified under EN17025. The data obtained showed that the incorporation of EAFD resulted in an increase of mechanical strength. Moreover, leaching tests performed according to the Europeans standards on the EAFD-block samples showed that the quantities of heavy metals leached from crushed blocks were within the regulatory limits. Thus the EAFD-blocks can be regarded as material of no environmental concern. Copyright © 2013 Elsevier B

  16. CO2 and Nd:YAP laser interaction with lithium disilicate and Zirconia dental ceramics: A preliminary study

    NASA Astrophysics Data System (ADS)

    Rocca, Jean-Paul; Fornaini, Carlo; Brulat-Bouchard, Nathalie; Bassel Seif, Samy; Darque-Ceretti, Evelyne

    2014-04-01

    Lithium disilicate and Zirconia ceramics offer a high level of accuracy when used in prosthetic dentistry. Their bonding using different resins is highly dependent on micro-mechanical interlocking and adhesive chemical bonding. Investigation of the performances of high strength ceramics when their surface is modified for chemical and mechanical bonding is then required. The aim of this study is to investigate the possibility of using laser for surface treatment of different high strength CAD/CAM ceramics and thus to improve their mechanical and chemical properties. Thirty two CAD/CAM ceramic discs were divided into two different groups: lithium disilicate ceramics (IPS e.max CAD®, Ivoclar, Vivadent, Italy) and Zirconia ceramics (IPS e.max ZirCAD®, Ivoclar, Vivadent, Italy). The Laser surface treatment was performed by Carbon Dioxide laser (Dream Pulse Laser®, Daeshin Enterprise Corp., Korea) at 20 W, 25 W and 30 W CW and by Neodymium Yttrium Aluminum Perovskite laser (Nd:YAP Lokki®, Lobel Medical, France) at 10 W and 30 Hz. Physical modifications of the irradiated ceramic discs were observed by scanning electron microscopy (SEM) and chemically analyzed by Energy-Dispersive Spectroscopy (EDS). Surface wettability was tested using the water drop test and the crystalline structure was investigated using X-ray diffraction (XRD). The macroscopic observation showed a shinier structure in all the groups, while at the SEM observation only CO2 25 W and 30 W treated groups showed cracks and fissures. In the conditions of this study, CO2 laser and Nd:YAP laser with the parameters used create chemical and physical surface modifications of the ceramics, indicating the possibility of an improvement in adhesion of the tested ceramics.

  17. Investigation of the Kinetic Energy Characterization of Advanced Ceramics

    DTIC Science & Technology

    2015-04-01

    of Science, under a US Army International Technology Center contract. These ceramic formulations were compared with standard armor-grade boron ...Experimental Methodology 1 3. Results and Discussion 4 3.1 Aluminum Performance Baseline 4 3.2 Ceramic Inspection 6 3.3 Boron Carbide 6 3.4 Silicon...Carbide 7 3.5 Boron Carbide–Aluminum Nitride 7 3.6 Boron Carbide–Vanadium Diboride 7 3.7 Titanium Nitride–Aluminum Nitride 8 3.8 Comparative

  18. Reflectance, Optical Properties, and Stability of Molybdenum/Strontium and Molybdenum/Yttrium Multilayer Mirrors

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

    Kjornrattanawanich, Benjawan

    2002-09-01

    The motivation of this work is to develop high reflectance normal-incidence multilayer mirrors in the 8-12 nm wavelength region for applications in astronomy and extreme ultraviolet lithography. To achieve this goal, Mo/Sr and Mo/Y multilayers were studied. These multilayers were deposited with a UHV magnetron sputtering system and their reflectances were measured with synchrotron radiation. High normal-incidence reflectances of 23% at 8.8 nm, 40.8% at 9.4 nm, and 48.3% at 10.5 nm were achieved. However, the reflectance of Mo/Sr multilayers decreased rapidly after exposure to air. Attempts to use thin layers of carbon to passivate the surface of Mo/Sr multilayers were unsuccessful. Experimental results on the refractive indexmore » $$\\tilde{n}$$ = 1-δ + iβ of yttrium and molybdenum in the 50-1300 eV energy region are reported in this work. This is the first time ever that values on the refractive index of yttrium are measured in this energy range. The absorption part β was determined through transmittance measurements. The dispersive part δ was calculated by means of the Kramers-Kronig formalism. The newly determined values of the refractive index of molybdenum are in excellent agreement with the published data. Those of yttrium are more accurate and contain fine structures around the yttrium M-absorption edges where Mo/Y multilayers operate. These improved sets of optical data lead to better design and modeling of the optical properties of Mo/Y multilayers. The reflectance quality of Mo/Y multilayers is dependent on their optical and structural properties. To correlate these properties with the multilayer reflectance, x-ray diffraction, Rutherford backscattering spectrometry, and transmission electron microscopy were used to analyze samples. Normal-incidence reflectances of 32.6% at 9.27 nm, 38.4% at 9.48 nm, and 29.6% at 9.46 nm were obtained from three representative Mo/Y multilayers which had about 0%, 25%, and 39% atomic oxygen assimilated in their

  19. Recovery of yttrium from fluorescent powder of cathode ray tube, CRT: Zn removal by sulphide precipitation

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

    Innocenzi, Valentina, E-mail: valentina.innocenzi1@univaq.it; De Michelis, Ida; Ferella, Francesco

    2013-11-15

    Highlights: • Treatment of fluorescent powder of CRT waste. • Factorial experimental designs to study acid leaching of fluorescent powder and the purification of leach liquors. • Recover of yttrium by precipitation using oxalic acid. • Suitable flowsheet to recover yttrium from fluorescent powder. - Abstract: This work is focused on the recovery of yttrium and zinc from fluorescent powder of cathode ray tube (CRT). Metals are extracted by sulphuric acid in the presence of hydrogen peroxide. Leaching tests are carried out according to a 2{sup 2} full factorial plan and the highest extraction yields for yttrium and zinc equalmore » to 100% are observed under the following conditions: 3 M of sulphuric acid, 10% v/v of H{sub 2}O{sub 2} concentrated solution at 30% v/v, 10% w/w pulp density, 70 °C and 3 h of reaction. Two series of precipitation tests for zinc are carried out: a 2{sup 2} full factorial design and a completely randomized factorial design. In these series the factors investigated are pH of solution during the precipitation and the amount of sodium sulphide added to precipitate zinc sulphide. The data of these tests are used to describe two empirical mathematical models for zinc and yttrium precipitation yields by regression analysis. The highest precipitation yields for zinc are obtained under the following conditions: pH equal to 2–2.5% and 10–12% v/v of Na{sub 2}S concentrated solution at 10% w/v. In these conditions the coprecipitation of yttrium is of 15–20%. Finally further yttrium precipitation experiments by oxalic acid on the residual solutions, after removing of zinc, show that yttrium could be recovered and calcined to obtain the final product as yttrium oxide. The achieved results allow to propose a CRT recycling process based on leaching of fluorescent powder from cathode ray tube and recovery of yttrium oxide after removing of zinc by precipitation. The final recovery of yttrium is 75–80%.« less

  20. Development of Advanced Environmental Barrier Coatings for SiC/SiC Ceramic Matrix Composites: Path Toward 2700 F Temperature Capability and Beyond

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Harder, Bryan; Hurst, Janet B.; Good, Brian; Costa, Gustavo; Bhatt, Ramakrishna T.; Fox, Dennis S.

    2017-01-01

    Advanced environmental barrier coating systems for SiC-SiC Ceramic Matrix Composite (CMC) turbine and combustor hot section components are currently being developed to meet future turbine engine emission and performance goals. One of the significant coating development challenges is to achieve prime-reliant environmental barrier coating systems to meet the future 2700F EBC-CMC temperature stability and environmental durability requirements. This presentation will emphasize recent NASA environmental barrier coating system testing and down-selects, particularly the development path and properties towards 2700-3000F durability goals by using NASA hafnium-hafnia-rare earth-silicon-silicate composition EBC systems for the SiC-SiC CMC turbine component applications. Advanced hafnium-based compositions for enabling next generation EBC and CMCs capabilities towards ultra-high temperature ceramic coating systems will also be briefly mentioned.

  1. Dependence of viscosity of suspensions of ceramic nanopowders in ethyl alcohol on concentration and temperature

    PubMed Central

    2012-01-01

    This work presents results of measurements of viscosity of suspensions including yttrium oxide (Y2O3), yttrium aluminum garnet (Y3Al5O12) and magnesium aluminum spinel (MgAl2O4) nanopowders in ethanol. Nanoparticles used in our research were either commercially available (Baikowski) or nanopowders newly developed in the Institute of Ceramics and Building Materials in Warsaw, Poland. The study was conducted in a wide range of shear rates (0.01 to 2,000 s−1) and temperature interval from -15°C to 20°C. A Haake Mars 2 rheometer from Thermo Fisher, Germany, was used in the Biophysics Laboratory at Rzeszów University of Technology. Most of the samples show a non-Newtonian behaviour. It was confirmed with a Rheo-NMR system from Bruker that 10% by weight of Y2O3 suspension is a non-Newtonian fluid. In this work, we also report an unexpected behaviour of the viscosity of some samples (Y2O3 and Y3Al5O12) due to sedimentation effect. PMID:22824064

  2. Using mixture design of experiments to assess the environmental impact of clay-based structural ceramics containing foundry wastes.

    PubMed

    Coronado, M; Segadães, A M; Andrés, A

    2015-12-15

    This work describes the leaching behavior of potentially hazardous metals from three different clay-based industrial ceramic products (wall bricks, roof tiles, and face bricks) containing foundry sand dust and Waelz slag as alternative raw materials. For each product, ten mixtures were defined by mixture design of experiments and the leaching of As, Ba, Cd, Cr, Cu, Mo, Ni, Pb, and Zn was evaluated in pressed specimens fired simulating the three industrial ceramic processes. The results showed that, despite the chemical, mineralogical and processing differences, only chrome and molybdenum were not fully immobilized during ceramic processing. Their leaching was modeled as polynomial equations, functions of the raw materials contents, and plotted as response surfaces. This brought to evidence that Cr and Mo leaching from the fired products is not only dependent on the corresponding contents and the basicity of the initial mixtures, but is also clearly related with the mineralogical composition of the fired products, namely the amount of the glassy phase, which depends on both the major oxides contents and the firing temperature. Copyright © 2015 Elsevier B.V. All rights reserved.

  3. Development of advanced space solar dynamic receiver

    NASA Astrophysics Data System (ADS)

    Abe, Yoshiyuki; Tanaka, Kotaro; Nomura, Osami; Kanari, Katsuhiko; Takahashi, Yoshio; Kamimoto, Masayuki

    Work on an advanced solar dynamic receiver is reviewed. The authors first describe the component test of the receiver tube with LiF in metallic containers, which was performed in a closed high-temperature He-Xe loop. They then give the details of the development of composite phase change materials, such as ceramic/molten salts or carbon/molten salts for advanced receiver concepts. As for SiC/LiF composites, the performance test of the receiver component will soon be ready to begin.

  4. Effect of Nd: YAG laser irradiation on surface properties and bond strength of zirconia ceramics.

    PubMed

    Liu, Li; Liu, Suogang; Song, Xiaomeng; Zhu, Qingping; Zhang, Wei

    2015-02-01

    This study investigated the effect of neodymium-doped yttrium aluminum garnet (Nd: YAG) laser irradiation on surface properties and bond strength of zirconia ceramics. Specimens of zirconia ceramic pieces were divided into 11 groups according to surface treatments as follows: one control group (no treatment), one air abrasion group, and nine laser groups (Nd: YAG irradiation). The laser groups were divided by applying with different output power (1, 2, or 3 W) and irradiation time (30, 60, or 90 s). Following surface treatments, the morphological characteristics of ceramic pieces was observed, and the surface roughness was measured. All specimens were bonded to resin cement. After, stored in water for 24 h and additionally aged by thermocycling, the shear bond strength was measured. Dunnett's t test and one-way ANOVA were performed as the statistical analyses for the surface roughness and the shear bond strength, respectively, with α = .05. Rougher surface of the ceramics could be obtained by laser irradiation with higher output power (2 and 3 W). However, cracks and defects were also found on material surface. The shear bond strength of laser groups was not obviously increased, and it was significantly lower than that of air abrasion group. No significant differences of the shear bond strength were found among laser groups treated with different output power or irradiation time. Nd: YAG laser irradiation cannot improve the surface properties of zirconia ceramics and cannot increase the bond strength of the ceramics. Enhancing irradiation power and extending irradiation time cannot induce higher bond strength of the ceramics and may cause material defect.

  5. NASA/CARES dual-use ceramic technology spinoff applications

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

    NASA has developed software that enables American industry to establish the reliability and life of ceramic structures in a wide variety of 21st Century applications. Designing ceramic components to survive at higher temperatures than the capability of most metals and in severe loading environments involves the disciplines of statistics and fracture mechanics. Successful application of advanced ceramics material properties and the use of a probabilistic brittle material design methodology. The NASA program, known as CARES (Ceramics Analysis and Reliability Evaluation of Structures), is a comprehensive general purpose design tool that predicts the probability of failure of a ceramic component as a function of its time in service. The latest version of this software, CARESALIFE, is coupled to several commercially available finite element analysis programs (ANSYS, MSC/NASTRAN, ABAQUS, COSMOS/N4, MARC), resulting in an advanced integrated design tool which is adapted to the computing environment of the user. The NASA-developed CARES software has been successfully used by industrial, government, and academic organizations to design and optimize ceramic components for many demanding applications. Industrial sectors impacted by this program include aerospace, automotive, electronic, medical, and energy applications. Dual-use applications include engine components, graphite and ceramic high temperature valves, TV picture tubes, ceramic bearings, electronic chips, glass building panels, infrared windows, radiant heater tubes, heat exchangers, and artificial hips, knee caps, and teeth.

  6. Corrosion resistant amorphous metals and methods of forming corrosion resistant amorphous metals

    DOEpatents

    Farmer, Joseph C.; Wong, Frank M.G.; Haslam, Jeffery J.; Yang, Nancy; Lavernia, Enrique J.; Blue, Craig A.; Graeve, Olivia A.; Bayles, Robert; Perepezko, John H.; Kaufman, Larry; Schoenung, Julie; Ajdelsztajn, Leo

    2014-07-15

    A system for coating a surface comprises providing a source of amorphous metal, providing ceramic particles, and applying the amorphous metal and the ceramic particles to the surface by a spray. The coating comprises a composite material made of amorphous metal that contains one or more of the following elements in the specified range of composition: yttrium (.gtoreq.1 atomic %), chromium (14 to 18 atomic %), molybdenum (.gtoreq.7 atomic %), tungsten (.gtoreq.1 atomic %), boron (.ltoreq.5 atomic %), or carbon (.gtoreq.4 atomic %).

  7. Corrosion resistant amorphous metals and methods of forming corrosion resistant amorphous metals

    DOEpatents

    Farmer, Joseph C [Tracy, CA; Wong, Frank M. G. [Livermore, CA; Haslam, Jeffery J [Livermore, CA; Yang, Nancy [Lafayette, CA; Lavernia, Enrique J [Davis, CA; Blue, Craig A [Knoxville, TN; Graeve, Olivia A [Reno, NV; Bayles, Robert [Annandale, VA; Perepezko, John H [Madison, WI; Kaufman, Larry [Brookline, MA; Schoenung, Julie [Davis, CA; Ajdelsztajn, Leo [Walnut Creek, CA

    2009-11-17

    A system for coating a surface comprises providing a source of amorphous metal, providing ceramic particles, and applying the amorphous metal and the ceramic particles to the surface by a spray. The coating comprises a composite material made of amorphous metal that contains one or more of the following elements in the specified range of composition: yttrium (.gtoreq.1 atomic %), chromium (14 to 18 atomic %), molybdenum (.gtoreq.7 atomic %), tungsten (.gtoreq.1 atomic %), boron (.ltoreq.5 atomic %), or carbon (.gtoreq.4 atomic %).

  8. Yttrium oxide based three dimensional metamaterials for visible light cloaking

    NASA Astrophysics Data System (ADS)

    Rai, Pratyush; Kumar, Prashanth S.; Varadan, Vijay K.; Ruffin, Paul; Brantley, Christina; Edwards, Eugene

    2014-04-01

    Metamaterial with negative refractive index is the key phenomenon behind the concept of a cloaking device to hide an object from light in visible spectrum. Metamaterials made of two and three dimensional lattices of periodically placed electromagnetic resonant cells can achieve absorption and propagation of incident electromagnetic radiation as confined electromagnetic fields confined to a waveguide as surface plasmon polaritons, which can be used for shielding an object from in-tune electromagnetic radiation. The periodicity and dimensions of resonant cavity determine the frequency, which are very small as compared to the wavelength of incident light. Till now the phenomena have been demonstrated only for lights in near infrared spectrum. Recent advancements in fabrication techniques have made it possible to fabricate array of three dimensional nanostructures with cross-sections as small as 25 nm that are required for negative refractive index for wavelengths in visible light spectrum of 400-700 nm and for wider view angle. Two types of metamaterial designs, three dimensional concentric split ring and fishnet, are considered. Three dimensional structures consisted of metal-dielectric-metal stacks. The metal is silver and dielectric is yttrium oxide, other than conventional materials such as FR4 and Duroid. High κ dielectric and high refractive index as well as large crystal symmetry of Yttrium oxide has been investigated as encapsulating medium. Dependence of refractive index on wavelength and bandwidth of negative refractive index region are analyzed for application towards cloaking from light in visible spectrum.

  9. Ceramic susceptor for induction bonding of metals, ceramics, and plastics

    NASA Technical Reports Server (NTRS)

    Fox, Robert L.; Buckley, John D.

    1991-01-01

    A thin (.005) flexible ceramic susceptor (carbon) was discovered. It was developed to join ceramics, plastics, metals, and combinations of these materials using a unique induction heating process. Bonding times for laboratory specimens comparing state of the art technology to induction bonding were cut by a factor of 10 to 100 times. This novel type of carbon susceptor allows for applying heat directly and only to the bondline without heating the entire structure, supports, and fixtures of a bonding assembly. The ceramic (carbon film) susceptor produces molten adhesive or matrix material at the bond interface. This molten material flows through the perforated susceptor producing a fusion between the two parts to be joined, which in many instances has proven to be stronger than the parent material. Bonding can be accomplished in 2 minutes on areas submitted to the inductive heating. Because a carbon susceptor is used in bonding carbon fiber reinforced plastics and ceramics, there is no radar signature or return making it an ideal process for joining advanced aerospace composite structures.

  10. Manufacture of high-density ceramic sinters

    NASA Technical Reports Server (NTRS)

    Hibata, Y.

    1986-01-01

    High density ceramic sinters are manufactured by coating premolded or presintered porous ceramics with a sealing material of high SiO2 porous glass or nitride glass and then sintering by hot isostatic pressing. The ceramics have excellent abrasion and corrosion resistances. Thus LC-10 (Si3N2 powder) and Y2O3-Al2O3 type sintering were mixed and molded to give a premolded porous ceramic (porosity 37%, relative bulk density 63%). The ceramic was dipped in a slurry containing high SiO2 porous glass and an alcohol solution of cellulose acetate and dried. The coated ceramic was treated in a nitrogen atmosphere and then sintered by hot isostatic pressing to give a dense ceramic sinter.

  11. Current Issues with Environmental Barrier Coatings for Ceramics and Ceramic Composites

    NASA Technical Reports Server (NTRS)

    Lee, Kang N.

    2004-01-01

    The environmental barrier coating (EBC) for SiC/SiC ceramic matrix composites and Si3N4 ceramics is an emerging field as the application of silicon-based ceramics in the gas turbine engine hot section is on the horizon, both for aero and industrial gas turbines. EBC is an enabling technology for silicon-based ceramics because these materials without an EBC cannot be used in combustion environments due to rapid surface recession. Significant progress in EBC development has been made during the last decade through various government-sponsored programs. Current EBCs are based on silicon, mullite (3Al2O3-2SiO2) and BSAS (barium strontium aluminum silicate with celsian structure). Volatility of BSAS, BSAS-silica chemical reaction, and low melting point of silicon limit temperature capability of current EBCs to about 1350 C for long-term applications. There is a need for higher temperature EBCs as the temperature capability of silicon-based ceramics continue to increase. Therefore, research is underway to develop EBCs with improved temperature capability compared to current EBCs. The current status and issues with the advanced EBC development efforts will be discussed.

  12. An experimental bioactive dental ceramic for metal-ceramic restorations: Textural characteristics and investigation of the mechanical properties.

    PubMed

    Goudouri, Ourania-Menti; Kontonasaki, Eleana; Papadopoulou, Lambrini; Manda, Marianthi; Kavouras, Panagiotis; Triantafyllidis, Konstantinos S; Stefanidou, Maria; Koidis, Petros; Paraskevopoulos, Konstantinos M

    2017-02-01

    The aim of this study was the evaluation of the textural characteristics of an experimental sol-gel derived feldspathic dental ceramic, which has already been proven bioactive and the investigation of its flexural strength through Weibull Statistical Analysis. The null hypothesis was that the flexural strength of the experimental and the commercial dental ceramic would be of the same order, resulting in a dental ceramic with apatite forming ability and adequate mechanical integrity. Although the flexural strength of the experimental ceramics was not statistically significant different compared to the commercial one, the amount of blind pores due to processing was greater. The textural characteristics of the experimental ceramic were in accordance with the standard low porosity levels reported for dental ceramics used for fixed prosthetic restorations. Feldspathic dental ceramics with typical textural characteristics and advanced mechanical properties as well as enhanced apatite forming ability can be synthesized through the sol-gel method. Copyright © 2016 Elsevier Ltd. All rights reserved.

  13. Advanced ceramic material for high temperature turbine tip seals

    NASA Technical Reports Server (NTRS)

    Vogan, J. W.; Solomon, N. G.; Stetson, A. R.

    1980-01-01

    Forty-one material systems were evaluated for potential use in turbine blade tip seal applications at 1370 C. Both ceramic blade tip inserts and abradable ceramic tip shoes were tested. Hot gas erosion, impact resistance, thermal stability, and dynamic rub performance were the criteria used in rating the various materials. Silicon carbide and silicon nitride were used, both as blade tips and abradables. The blade tip inserts were fabricated by hot pressing while low density and honeycomb abradables were sintered or reaction bonded.

  14. High-Performance Protonic Ceramic Fuel Cells with Thin-Film Yttrium-Doped Barium Cerate-Zirconate Electrolytes on Compositionally Gradient Anodes.

    PubMed

    Bae, Kiho; Lee, Sewook; Jang, Dong Young; Kim, Hyun Joong; Lee, Hunhyeong; Shin, Dongwook; Son, Ji-Won; Shim, Joon Hyung

    2016-04-13

    In this study, we used a compositionally gradient anode functional layer (AFL) consisting of Ni-BaCe(0.5)Zr(0.35)Y(0.15)O(3-δ) (BCZY) with increasing BCZY contents toward the electrolyte-anode interface for high-performance protonic ceramic fuel cells. It is identified that conventional homogeneous AFLs fail to stably accommodate a thin film of BCZY electrolyte. In contrast, a dense 2 μm thick BCZY electrolyte was successfully deposited onto the proposed gradient AFL with improved adhesion. A fuel cell containing this thin electrolyte showed a promising maximum peak power density of 635 mW cm(-2) at 600 °C, with an open-circuit voltage of over 1 V. Impedance analysis confirmed that minimizing the electrolyte thickness is essential for achieving a high power output, suggesting that the anode structure is important in stably accommodating thin electrolytes.

  15. Immobilization of actinides in stable mineral type and ceramic materials (high temperature synthesis)

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

    Starkov, O.; Konovalov, E.

    1996-05-01

    Alternative vitrification technologies are being developed in the world for the immobilization of high radioactive waste in materials with improved thermodynamic stability, as well as improved chemical and thermal stability and stability to radiation. Oxides, synthesized in the form of analogs to rock-forming minerals and ceramics, are among those materials that have highly stable properties and are compatible with the environment. In choosing the appropriate material, we need to be guided by its geometric stability, the minimal number of cations in the structure of the material and the presence of structural elements in the mineral that are isomorphs of uraniummore » and thorium, actinoids found in nature. Rare earth elements, yttrium, zirconium and calcium are therefore suitable. The minerals listed in the table (with the exception of the zircon) are pegatites by origin, i.e. they are formed towards the end of the magma crystallization of silicates form the residual melt, enriched with Ta, Nb, Ti, Zr, Ce, Y, U and Th. Uranium and thorium in the form of isomorphic admixtures form part of the lattice of the mineral. These minerals, which are rather simple in composition and structure and are formed under high temperatures, may be viewed as natural physio-chemical systems that are stable and long-lived in natural environments. The similarity of the properties of actinoids and lanthanoids plays an important role in the geochemistry of uranium and thorium; however, uranium (IV) is closer to the {open_quotes}heavy{close_quotes} group of lanthanoids (the yttrium group) while thorium (IV) is closer to the {open_quotes}light{close_quotes} group (the cerium group). That is why rare earth minerals contain uranium and thorium in the form of isomorphic admixtures.« less

  16. [Ceramic-ceramic articulation in uncemented total hip arthroplasty].

    PubMed

    Synder, Marek; Drobniewski, Marek; Kozłowski, Piotr; Grzegorzewski, Andrzej

    2005-01-01

    The main problem in total hip arthroplasty (THA) surgery is aseptic loosening of prosthesis components. In most cases the phagocytes reaction against the wear particle during the hip movement is responsible for aseptic prosthesis loosening. To prevent this reaction different hip articulation are invented to reduce this reaction. One of these solutions is ceramic-ceramic hip prosthesis articulation. The aim of this study was to evaluate the long-term results in patients who were treated because of coxarthrosis by means of ceramic-ceramic hip prosthesis. We analyzed 258 primary THA (222 patients, 116 women and 106 men) who were treated because of advanced coxarthrosis by Mittelmeier type hip endoprosthesis (ceramic-ceramic articulation). The mean age of patients at the surgery was 45.6 years and a mean follow-up 10.2 years. In most of our cases the idiopathic, traumatic and dysplastic coxarthrosis was noted. For clinical evaluation the classification system proposed by Merle d'Aubigne and Postel with Charnley modification was used. For radiological evaluation of the steam implantation the classification system proposed by De Lee and Charnley was used and for the cup implantation the system by Gruen and Moreland. In 87 patients (33.7%) the final results was graded as very good, in 96 (37.2%) as good, in 47 (18.2%) as satisfactory and in 28 patients (10.9%) the final results was poor. In analyzed group in 13 patients (5.0%) the revision surgery was necessary. The long-term results of THA with the use of Mittelmeier type of hip prosthesis presented a very low percentage of aseptic loosening. This type of prosthesis gives very high patients satisfaction.

  17. Design and evaluation of experimental ceramic automobile thermal reactors

    NASA Technical Reports Server (NTRS)

    Stone, P. L.; Blankenship, C. P.

    1974-01-01

    The paper summarizes the results obtained in an exploratory evaluation of ceramics for automobile thermal reactors. Candidate ceramic materials were evaluated in several reactor designs using both engine dynamometer and vehicle road tests. Silicon carbide contained in a corrugated metal support structure exhibited the best performance, lasting 1100 hours in engine dynamometer tests and for more than 38,600 kilimeters (24,000 miles) in vehicle road tests. Although reactors containing glass-ceramic components did not perform as well as silicon carbide, the glass-ceramics still offer good potential for reactor use with improved reactor designs.

  18. Stress Corrosion of Ceramic Materials

    DTIC Science & Technology

    1981-10-01

    stresses are liable to fail after an indeterminate period of time, leading to a considerable uncertainty in the safe design stress. One of the objectives...of modern ceramics technology is to reduce the uncertainty associated with structural design , and hence, to improve our capabilities of designing ...processes that occur during stress corrosion cracking. Recent advances in th~earea of structural design with ceramic materials have lead to several

  19. Ceramic composites for rocket engine turbines

    NASA Technical Reports Server (NTRS)

    Herbell, Thomas P.; Eckel, Andrew J.

    1991-01-01

    The use of ceramic materials in the hot section of the fuel turbopump of advanced reusable rocket engines promises increased performance and payload capability, improved component life and economics, and greater design flexibility. Severe thermal transients present during operation of the Space Shuttle Main Engine (SSME), push metallic components to the limit of their capabilities. Future engine requirements might be even more severe. In phase one of this two-phase program, performance benefits were quantified and continuous fiber reinforced ceramic matrix composite components demonstrated a potential to survive the hostile environment of an advanced rocket engine turbopump.

  20. Durability of resin cement bond to aluminium oxide and zirconia ceramics after air abrasion and laser treatment.

    PubMed

    Foxton, Richard M; Cavalcanti, Andrea N; Nakajima, Masatoshi; Pilecki, Peter; Sherriff, Martyn; Melo, Luciana; Watson, Timothy F

    2011-02-01

    The erbium laser has been introduced for cutting enamel and dentin and may have an application in the surface modification of high-strength aluminum oxide and zirconia ceramics. The aim of this study was to evaluate the durability of the bond of conventional dual-cured resin cements to Procera Al(2)O(3) and zirconium oxide ceramics after surface treatment with air abrasion and erbium laser. One hundred twenty Al(2)O(3) and 120 zirconia specimens measuring 3 × 3 × 0.7 mm(3) were divided equally into three groups, and their surfaces treated as follows: either untreated (controls), air abraded with Al(2)O(3) particles, or erbium-laser-treated at a power setting of 200 mJ. The surface of each specimen was then primed and bonded with one of two dual-cured resin cements (either SCP-100 Ceramic Primer and NAC-100 or Monobond S and Variolink II) using a 1-mm thick Tygon tube mold with a 0.75-mm internal bore diameter. After 24 hours and 6 months of water storage at 37°C, a microshear bond strength test was performed at a crosshead speed of 1 mm/min. Surface morphology was examined using a confocal microscope, and failure modes were observed using an optical microscope. The data were analyzed using the Kaplan-Meier nonparametric survival analysis. In the case of zirconia, air abrasion and Erbium:yttrium-aluminum-garnet (Er:YAG) laser treatment of the ceramic surface resulted in a significant reduction in the bond strengths of both resin cements after 6 months water storage; however, when the zirconia surface was left untreated, the SCP-100/NAC-100 group did not significantly reduce in bond strength. In the case of alumina, no treatment, air abrasion and Er:YAG laser treatment of the surface led to no significant reduction in the bond strengths of the three SCP-100/NAC-100 groups after 6 months water storage, whereas all three Monobond S/Variolink II groups showed a significant reduction. Er:YAG laser treatment of the zirconia surface did not result in a durable resin

  1. Light-weight black ceramic insulation

    NASA Technical Reports Server (NTRS)

    Hsu, Ming-Ta S. (Inventor); Chen, Timothy S. (Inventor)

    2003-01-01

    Ultra-high temperature, light-weight, black ceramic insulation having a density ranging from about 0.12 g/cc. to 0.6 g/cc. such as ceramic tile is obtained by pyrolyzing siloxane gels derived from the reaction of at least one organo dialkoxy silane and at least one tetralkoxy silane in an acid or base liquid medium. The reaction mixture of the tetra- and dialkoxy silanes also may contain an effective amount of a mono- or trialkoxy silane to obtain the siloxane gels. The siloxane gels are dried at ambient temperatures and pressures to form siloxane ceramic precursors without significant shrinkage. The siloxane ceramic precursors are subsequently pyrolyzed, in an inert atmosphere, to form the black ceramic insulation comprising atoms of silicon, carbon and oxygen. The ceramic insulation can be characterized as a porous, uniform ceramic tile resistant to oxidation at temperatures ranging as high as 1700.degree. C., and particularly useful as lightweight tiles for spacecraft and other high-temperature insulation applications.

  2. Ceramic technology for solar thermal receivers

    NASA Technical Reports Server (NTRS)

    Kudirka, A. A.; Smoak, R. H.

    1981-01-01

    The high-temperature capability, resistance to corrosive environments and non-strategic nature of ceramics have prompted applications in the solar thermal field whose advantages over metallic devices of comparable performance may begin to be assessed. It is shown by a survey of point-focusing receiver designs employing a variety of ceramic compositions and fabrication methods that the state-of-the-art in structural ceramics is not sufficiently advanced to fully realize the promised benefits of higher temperature capabilities at lower cost than metallic alternatives. The ceramics considered include alumina, berylia, magnesia, stabilized zirconia, fused silica, silicon nitride, silicon carbide, mullite and cordierite, processed by such methods as isostatic pressing, dry pressing, slip casting, extrusion, calendaring and injection molding.

  3. Boron/Carbon/Silicon/Nitrogen Ceramics And Precursors

    NASA Technical Reports Server (NTRS)

    Riccitiello, Salvatore; Hsu, Ming TA; Chen, Timothy S.

    1996-01-01

    Ceramics containing various amounts of boron, carbon, silicon, and nitrogen made from variety of polymeric precursors. Synthesized in high yield from readily available and relatively inexpensive starting materials. Stable at room temperature; when polymerized, converted to ceramics in high yield. Ceramics resist oxidation and other forms of degradation at high temperatures; used in bulk to form objects or to infiltrate other ceramics to obtain composites having greater resistance to oxidation and high temperatures.

  4. Effects of Different Surface Treatment Methods and MDP Monomer on Resin Cementation of Zirconia Ceramics an In Vitro Study

    PubMed Central

    Tanış, Merve Çakırbay; Akçaboy, Cihan

    2015-01-01

    Introduction: Resin cements are generally preferred for cementation of zirconia ceramics. Resin bonding of zirconia ceramics cannot be done with the same methods of traditional ceramics because zirconia is a silica-free material. In recent years, many methods have been reported in the literature to provide the resin bonding of zirconia ceramics. The purpose of this in vitro study is to evaluate effects of different surface treatments and 10-metacryloxydecyl dihydrogen phosphate (MDP) monomer on shear bond strength between zirconia and resin cement. Methods: 120 zirconia specimens were treated as follows: Group I: sandblasting, group II: sandblasting + tribochemical silica coating + silane, group III: sandblasting + Nd:YAG (neodymium: yttrium-aluminum-garnet) laser. One specimen from each group was evaluated under scanning electron microscope (SEM). Specimens in each group were bonded either with conventional resin cement Variolink II or with a MDP containing resin cement Panavia F2.0. Subgroups of bonded specimens were stored in distilled water (37°C) for 24 hours or 14 days. Following water storage shear bond strength test was performed at a crosshead speed of 1 mm/min in a universal test machine. Then statistical analyses were performed. Results: Highest shear bond strength values were observed in group II. No significant difference between group I and III was found when Panavia F2.0 resin cement was used. When Variolink II resin cement was used group III showed significantly higher bond strength than group I. In group I, Panavia F2.0 resin cement showed statistically higher shear bond strength than Variolink II resin cement. In group II no significant difference was found between resin cements. No significant difference was found between specimens stored in 37°C distilled water for 24 hours and 14 days. In group I surface irregularities with sharp edges and grooves were observed. In group II less roughened surface was observed with silica particles. In group

  5. Effects of Different Surface Treatment Methods and MDP Monomer on Resin Cementation of Zirconia Ceramics an In Vitro Study.

    PubMed

    Tanış, Merve Çakırbay; Akçaboy, Cihan

    2015-01-01

    Resin cements are generally preferred for cementation of zirconia ceramics. Resin bonding of zirconia ceramics cannot be done with the same methods of traditional ceramics because zirconia is a silica-free material. In recent years, many methods have been reported in the literature to provide the resin bonding of zirconia ceramics. The purpose of this in vitro study is to evaluate effects of different surface treatments and 10-metacryloxydecyl dihydrogen phosphate (MDP) monomer on shear bond strength between zirconia and resin cement. 120 zirconia specimens were treated as follows: Group I: sandblasting, group II: sandblasting + tribochemical silica coating + silane, group III: sandblasting + Nd:YAG (neodymium: yttrium-aluminum-garnet) laser. One specimen from each group was evaluated under scanning electron microscope (SEM). Specimens in each group were bonded either with conventional resin cement Variolink II or with a MDP containing resin cement Panavia F2.0. Subgroups of bonded specimens were stored in distilled water (37°C) for 24 hours or 14 days. Following water storage shear bond strength test was performed at a crosshead speed of 1 mm/min in a universal test machine. Then statistical analyses were performed. Highest shear bond strength values were observed in group II. No significant difference between group I and III was found when Panavia F2.0 resin cement was used. When Variolink II resin cement was used group III showed significantly higher bond strength than group I. In group I, Panavia F2.0 resin cement showed statistically higher shear bond strength than Variolink II resin cement. In group II no significant difference was found between resin cements. No significant difference was found between specimens stored in 37°C distilled water for 24 hours and 14 days. In group I surface irregularities with sharp edges and grooves were observed. In group II less roughened surface was observed with silica particles. In group III surface microcracks

  6. Fabrication and Characterization of Dense Zirconia and Zirconia-Silica Ceramic Nanofibers

    PubMed Central

    Guo, Guangqing; Fan, Yuwei

    2011-01-01

    The objective of this study was to prepare dense zirconia-yttria (ZY), zirconia-silica (ZS) and zirconia-yttria-silica (ZYS) nanofibers as reinforcing elements for dental composites. Zirconium (IV) propoxide, yttrium nitrate hexahydrate, and tetraethyl orthosilicate (TEOS) were used as precursors for the preparation of zirconia, yttria, and silica sols. A small amount (1–1.5 wt%) of polyethylene oxide (PEO) was used as a carry polymer. The sols were preheated at 70 °C before electrospinning and their viscosity was measured with a viscometer at different heating time. The gel point was determined by viscosity–time (η–t) curve. The ZY, ZS and ZYS gel nanofibers were prepared using a special reactive electrospinning device under the conditions near the gel point. The as-prepared gel nanofibers had diameters between 200 and 400 nm. Dense (nonporous) ceramic nanofibers of zirconia-yttria (96/4), zirconia-silica (80/20) and zirconia-yttria-silica (76.8/3.2/20) with diameter of 100–300 nm were obtained by subsequent calcinations at different temperatures. The gel and ceramic nanofibers obtained were characterized by scanning electron microscope (SEM), high-resolution field-emission scanning electron microscope (FE-SEM), thermogravimetric analyzer (TGA), differential scanning calorimeter (DSC), Fourier transform infrared spectrometer (FT-IR), and X-ray diffraction (XRD). SEM micrograph revealed that ceramic ZY nanofibers had grained structure, while ceramic ZS and ZYS nanofibers had smooth surfaces, both showing no visible porosity under FE-SEM. Complete removal of the polymer PEO was confirmed by TGA/DSC and FT-IR. The formation of tetragonal phase of zirconia and amorphous silica was proved by XRD. In conclusion, dense zirconia-based ceramic nanofibers can be fabricated using the new reactive sol–gel electrospinning technology with minimum organic polymer additives. PMID:21133090

  7. Advanced bredigite-containing magnesium-matrix composites for biodegradable bone implant applications.

    PubMed

    Dezfuli, Sina Naddaf; Huan, Zhiguang; Mol, Arjan; Leeflang, Sander; Chang, Jiang; Zhou, Jie

    2017-10-01

    The present research was aimed at developing magnesium-matrix composites that could allow effective control over their physiochemical and mechanical responses when in contact with physiological solutions. A biodegradable, bioactive ceramic - bredigite was chosen as the reinforcing phase in the composites, based on the hypothesis that the silicon- and magnesium-containing ceramic could protect magnesium from fast corrosion and at the same time stimulate cell proliferation. Methods to prepare composites with integrated microstructures - a prerequisite to achieve controlled biodegradation were developed. A systematic experimental approach was taken in order to elucidate the in vitro biodegradation mechanisms and kinetics of the composites. It was found that the composites with 20-40% homogenously dispersed bredigite particles, prepared from powders, could indeed significantly decrease the degradation rate of magnesium by up to 24 times. Slow degradation of the composites resulted in the retention of the mechanical integrity of the composites within the strength range of cortical bone after 12days of immersion in a cell culture medium. Cell attachment, cytotoxicity and bioactivity tests confirmed the stimulatory effects of bredigite embedded in the composites on the attachment, viability and differentiation of bone marrow stromal cells. Thus, the multiple benefits of adding bredigite to magnesium in enhancing degradation behavior, mechanical properties, biocompatibility and bioactivity were obtained. The results from this research showed the excellent potential of the bredigite-containing composites for bone implant applications, thus warranting further in vitro and in vivo research. Copyright © 2017 Elsevier B.V. All rights reserved.

  8. Predictive Surface Roughness Model for End Milling of Machinable Glass Ceramic

    NASA Astrophysics Data System (ADS)

    Mohan Reddy, M.; Gorin, Alexander; Abou-El-Hossein, K. A.

    2011-02-01

    Advanced ceramics of Machinable glass ceramic is attractive material to produce high accuracy miniaturized components for many applications in various industries such as aerospace, electronics, biomedical, automotive and environmental communications due to their wear resistance, high hardness, high compressive strength, good corrosion resistance and excellent high temperature properties. Many research works have been conducted in the last few years to investigate the performance of different machining operations when processing various advanced ceramics. Micro end-milling is one of the machining methods to meet the demand of micro parts. Selecting proper machining parameters are important to obtain good surface finish during machining of Machinable glass ceramic. Therefore, this paper describes the development of predictive model for the surface roughness of Machinable glass ceramic in terms of speed, feed rate by using micro end-milling operation.

  9. Use of a two-body belt abrasion test to measure the grindability of advanced ceramic materials

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

    Blau, P.J.; Zanoria, E.S.

    1998-07-01

    Structural materials, such as superalloys, intermetallic alloys and engineering ceramics, have been developed to achieve high hardness, high temperature strength, and high fracture toughness. However, these strong materials also tend to be difficult to grind and finish. In the 1990's, the US Department of Energy supported a series of projects to help reduce the cost of machining advanced ceramics. The same properties that make engineering materials attractive for use on severe thermal and mechanical environments (e.g., high hardness, high temperature strength, high fracture toughness) generally tend to make those materials difficult to grind and finish. In the mid-1990's, a beltmore » abrasion test was developed under subcontract to Oak Ridge National Laboratory to help to assess the grindability of structural ceramic materials. The procedure involves applying a 10 N normal force to the end face of a 3 x 4 mm cross-section test bar for 30 seconds which is rubbed against a wet, 220 grit diamond belt moving at 10 m/s. By measuring the change in the bar length after at least six 30-second tests, a belt grindability index is computed and expressed using the same units as a traditional wear factor (i.e., mm{sup 3}/N-m). The test has shown an excellent capability to discriminate not only between ceramics of different basic compositions, e.g., Al{sub 2}O{sub 3}, SiC, and Si{sub 3}N{sub 4}, but also between different lots of the same basic ceramic. Test-to-test variability decreases if the belt is worn in on the material of interest. The surface roughness of the abraded ends of the test specimens does not correlate directly with the belt grindability index, but instead reflects another attribute of grindability; namely the ability of a material to abrade smoothly without leaving excessive rough and pitted areas.« less

  10. Advanced ceramic material for high temperature turbine tip seals

    NASA Technical Reports Server (NTRS)

    Solomon, N. G.; Vogan, J. W.

    1978-01-01

    Ceramic material systems are being considered for potential use as turbine blade tip gas path seals at temperatures up to 1370 1/4 C. Silicon carbide and silicon nitride structures were selected for study since an initial analysis of the problem gave these materials the greatest potential for development into a successful materials system. Segments of silicon nitride and silicon carbide materials over a range of densities, processed by various methods, a honeycomb structure of silicon nitride and ceramic blade tip inserts fabricated from both materials by hot pressing were tested singly and in combination. The evaluations included wear under simulated engine blade tip rub conditions, thermal stability, impact resistance, machinability, hot gas erosion and feasibility of fabrication into engine components. The silicon nitride honeycomb and low-density silicon carbide using a selected grain size distribution gave the most promising results as rub-tolerant shroud liners. Ceramic blade tip inserts made from hot-pressed silicon nitride gave excellent test results. Their behavior closely simulated metal tips. Wear was similar to that of metals but reduced by a factor of six.

  11. Glass formation and crystallization in high-temperature glass-ceramics and Si3N4

    NASA Technical Reports Server (NTRS)

    Drummond, Charles H., III

    1991-01-01

    The softening of glassy grain boundaries in ceramic matrix composites and Si3N4 at high temperatures reduces mechanical strength and the upper-use temperature. By crystallizing this glass to a more refractory crystalline phase, a material which performs at higher temperatures may result. Three systems were examined: a cordierite composition with ZrO2 as a nucleating agent; celsian compositions; and yttrium silicate glasses both in bulk and intergranular in Si3N4. For the cordierite compositions, a series of metastable phases was obtained. The crystallization of these compositions was summarized in terms of metastable ternary isothermal sections. Zircon formed at the expense of ZrO2 and spinel. In SiC composites, the transformations were slower. In celsian, two polymorphs were crystallized. One phase, hexacelsian, which always crystallized, even when metastable, had an undesirable volume change. The other phase, celsian, was very difficult to crystallize. In yttrium silicate bulk glasses, similar in composition to the intergranular glass in Si3N4, a number of polymorphs of Y2Si2O7 were crystallized. The conditions under which these polymorphs formed are compared with crystallization in Si3N4.

  12. Evaluation of sol-gel based magnetic 45S5 bioglass and bioglass-ceramics containing iron oxide.

    PubMed

    Shankhwar, Nisha; Srinivasan, A

    2016-05-01

    Multicomponent oxide powders with nominal compositions of (45-x)·SiO2·24.5CaO·24.5Na2O·6P2O5xFe2O3 (in wt.%) were prepared by a modified sol-gel procedure. X-ray diffraction (XRD) patterns and high resolution transmission electron microscope images of the sol-gel products show fully amorphous structure for Fe2O3 substitutions up to 2 wt.%. Sol-gel derived 43SiO2·24.5CaO·24.5Na2O·6P2O5·2Fe2O3 glass (or bioglass 45S5 with SiO2 substituted with 2 wt.% Fe2O3), exhibited magnetic behavior with a coercive field of 21 Oe, hysteresis loop area of 33.25 erg/g and saturation magnetization of 0.66 emu/g at an applied field of 15 kOe at room temperature. XRD pattern of this glass annealed at 850 °C for 1h revealed the formation of a glass-ceramic containing sodium calcium silicate and magnetite phases in nanocrystalline form. Temperature dependent magnetization and room temperature electron spin resonance data have been used to obtain information on the magnetic phase and distribution of iron ions in the sol-gel glass and glass-ceramic samples. Sol-gel derived glass and glass-ceramic exhibit in-vitro bioactivity by forming a hydroxyapatite surface layer under simulated physiological conditions and their bio-response is superior to their melt quenched bulk counterparts. This new form of magnetic bioglass and bioglass ceramics opens up new and more effective biomedical applications. Copyright © 2016 Elsevier B.V. All rights reserved.

  13. New high boron content polyborane precursors to advanced ceramic materials: New syntheses, new applications

    NASA Astrophysics Data System (ADS)

    Guron, Marta

    There is a need for new synthetic routes to high boron content materials for applications as polymeric precursors to ceramics, as well as in neutron shielding and potential medical applications. To this end, new ruthenium-catalyzed olefin metathesis routes have been devised to form new complex polyboranes and polymeric species. Metathesis of di-alkenyl substituted o-carboranes allowed the synthesis of ring-closed products fused to the carborane cage, many of which are new compounds and one that offers a superior synthetic method to one previously published. Acyclic diene metathesis of di-alkenyl substituted m-carboranes resulted in the formation of new main-chain carborane-containing polymers of modest molecular weights. Due to their extremely low char yields, and in order to explore other metathesis routes, ring opening metathesis polymerization (ROMP) was used to generate the first examples of poly(norbornenyl- o-carboranes). Monomer synthesis was achieved via a two-step process, incorporating Ti-catalyzed hydroboration to make 6-(5-norbornenyl)-decaborane, followed by alkyne insertion in ionic liquid media to achieve 1,2-R2 -3-norbornenyl o-carborane species. The monomers were then polymerized using ROMP to afford several examples of poly(norbornenyl- o-carboranes) with relatively high molecular weights. One such polymer, [1-Ph, 3-(=CH2-C5H7-CH2=)-1,2-C 2B10H10]n, had a char yield very close to the theoretical char yield of 44%. Upon random copolymerization with poly(6-(5-norbornenyl) decaborane), char yields significantly increased to 80%, but this number was well above the theoretical value implicating the formation of a boron-carbide/carbon ceramic. Finally, applications of polyboranes were explored via polymer blends toward the synthesis of ceramic composites and the use of polymer precursors as reagents for potential ultra high temperature ceramic applications. Upon pyrolysis, polymer blends of poly(6-(5-norbornenyl)-decaborane) and poly

  14. Holmium: yttrium aluminum garnet laser-assisted endoscopic sinus surgery: laboratory experience.

    PubMed

    Shapshay, S M; Rebeiz, E E; Bohigian, R K; Hybels, R L; Aretz, H T; Pankratov, M M

    1991-02-01

    Endoscopic sinus surgery has gained wide acceptance since its introduction into the United States. Complex sinus anatomy and troublesome bleeding have been associated with complications, which vary in severity from synechia to blindness and leakage of cerebrospinal fluid. Endoscopic sinus surgery using a holmium: yttrium aluminum garnet pulsed solid-state laser oscillating at 2.1 microns with fiberoptic delivery was performed in the laboratory, and the results were compared with those of conventional endoscopic sinus surgery. Three beagle dogs, six human cadaver heads, and one calf head were used in the in vivo and in vitro studies to evaluate the bone ablation, tissue coagulation, and hemostatic properties of the holmium: yttrium aluminum garnet laser. Modified endoscopic telescopes for sinus surgery, a newly developed handpiece for fiberoptic delivery, and other surgical instruments were used. The results indicate that the holmium: yttrium aluminum garnet laser and new delivery instrumentation provide good hemostasis and controlled soft-tissue ablation and bone removal. The access to all sinuses in the human cadaver model was very good. The canine in vivo study showed delayed but complete healing on the laser-treated side. Clinical evaluation of the holmium: yttrium aluminum garnet laser is warranted to increase the precision and safety of endoscopic sinus surgery.

  15. Monte carlo simulations of Yttrium reaction rates in Quinta uranium target

    NASA Astrophysics Data System (ADS)

    Suchopár, M.; Wagner, V.; Svoboda, O.; Vrzalová, J.; Chudoba, P.; Tichý, P.; Kugler, A.; Adam, J.; Závorka, L.; Baldin, A.; Furman, W.; Kadykov, M.; Khushvaktov, J.; Solnyshkin, A.; Tsoupko-Sitnikov, V.; Tyutyunnikov, S.; Bielewicz, M.; Kilim, S.; Strugalska-Gola, E.; Szuta, M.

    2017-03-01

    The international collaboration Energy and Transmutation of Radioactive Waste (E&T RAW) performed intensive studies of several simple accelerator-driven system (ADS) setups consisting of lead, uranium and graphite which were irradiated by relativistic proton and deuteron beams in the past years at the Joint Institute for Nuclear Research (JINR) in Dubna, Russia. The most recent setup called Quinta, consisting of natural uranium target-blanket and lead shielding, was irradiated by deuteron beams in the energy range between 1 and 8 GeV in three accelerator runs at JINR Nuclotron in 2011 and 2012 with yttrium samples among others inserted inside the setup to measure the neutron flux in various places. Suitable activation detectors serve as one of possible tools for monitoring of proton and deuteron beams and for measurements of neutron field distribution in ADS studies. Yttrium is one of such suitable materials for monitoring of high energy neutrons. Various threshold reactions can be observed in yttrium samples. The yields of isotopes produced in the samples were determined using the activation method. Monte Carlo simulations of the reaction rates leading to production of different isotopes were performed in the MCNPX transport code and compared with the experimental results obtained from the yttrium samples.

  16. Antibacterial and antibiofilm properties of yttrium fluoride nanoparticles

    PubMed Central

    Lellouche, Jonathan; Friedman, Alexandra; Gedanken, Aharon; Banin, Ehud

    2012-01-01

    Antibiotic resistance has prompted the search for new agents that can inhibit bacterial growth. Moreover, colonization of abiotic surfaces by microorganisms and the formation of biofilms is a major cause of infections associated with medical implants, resulting in prolonged hospitalization periods and patient mortality. In this study we describe a water-based synthesis of yttrium fluoride (YF3) nanoparticles (NPs) using sonochemistry. The sonochemical irradiation of an aqueous solution of yttrium (III) acetate tetrahydrate [Y(Ac)3 · (H2O)4], containing acidic HF as the fluorine ion source, yielded nanocrystalline needle-shaped YF3 particles. The obtained NPs were characterized by scanning electron microscopy and X-ray elemental analysis. NP crystallinity was confirmed by electron and powder X-ray diffractions. YF3 NPs showed antibacterial properties against two common bacterial pathogens (Escherichia coli and Staphylococcus aureus) at a μg/mL range. We were also able to demonstrate that antimicrobial activity was dependent on NP size. In addition, catheters were surface modified with YF3 NPs using a one-step synthesis and coating process. The coating procedure yielded a homogeneous YF3 NP layer on the catheter, as analyzed by scanning electron microscopy and energy dispersive spectroscopy. These YF3 NP-modified catheters were investigated for their ability to restrict bacterial biofilm formation. The YF3 NP-coated catheters were able to significantly reduce bacterial colonization compared to the uncoated surface. Taken together, our results highlight the potential to further develop the concept of utilizing these metal fluoride NPs as novel antimicrobial and antibiofilm agents, taking advantage of their low solubility and providing extended protection. PMID:23152681

  17. EMBOLIZATION OF DOG PROSTATES WITH YTTRIUM-90 MICROSPHERES

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

    Greene, W.M.

    1963-10-01

    Experiments exploring means for the protection of adjacent normal tissue while delivering a destructive dose of radiation to malignant tissue were conducted. By injection of radioactive ceramic spheres or particles, too large to pass through capillaries or arteriovenous shunts, relatively high doses of radiation can be distributed homogeneously to a circumscribed area. Attempts were made to determine the uniformity of distribution and the radiation effect of varying doses of spheres injected into the arterial supply of the dog prostate. Nonradioactive and radioactive ceramic microspheres of 60 mu dia were used since this size exceeds the diameter of capillaries and arteriovenousmore » shunts. Yttrium-90 microspheres of varying radioactivity were used. Doses injected into right and left hypogastric arteries varied from 0.69 to 28.4 mc/side (92-1260 mc/ g prostate). Homogeneous distribution of radioactivity within the prostate was demonstrated by autoradiography. Distribution to some other organs (rectum, penis, and bladder) occurred because arterial supply to these structures was not isolated and occluded. The amount of radioactivity found in the lungs suggested more venous drainage in some cases than seemed apparent, and because of the infarctions of pelvic organs may have leaked radioactive spheres into the venous circuit. In 6 of the 8 dogs which died prematurely (2 to 7 days after surgery) obvious infarction of the prostate and in some other pelvic structures had occurred. That the radioactivity contributed to the infarction is suggested by the results in the dogs which received large doses of radioactivity (18.9 and 28.4 mc per side) in minimal amounts of spheres (100to 150 mg per side). The intensely concentrated radioactivity within the arteriolar lumens may have caused vasculitis and subsequent thrombosis. Although homogeneous destruction of the prostate gland occurred, the effect of a given dose ranged unpredictably through three groups: no apparent

  18. Integrated Design Software Predicts the Creep Life of Monolithic Ceramic Components

    NASA Technical Reports Server (NTRS)

    1996-01-01

    Significant improvements in propulsion and power generation for the next century will require revolutionary advances in high-temperature materials and structural design. Advanced ceramics are candidate materials for these elevated-temperature applications. As design protocols emerge for these material systems, designers must be aware of several innate features, including the degrading ability of ceramics to carry sustained load. Usually, time-dependent failure in ceramics occurs because of two different, delayedfailure mechanisms: slow crack growth and creep rupture. Slow crack growth initiates at a preexisting flaw and continues until a critical crack length is reached, causing catastrophic failure. Creep rupture, on the other hand, occurs because of bulk damage in the material: void nucleation and coalescence that eventually leads to macrocracks which then propagate to failure. Successful application of advanced ceramics depends on proper characterization of material behavior and the use of an appropriate design methodology. The life of a ceramic component can be predicted with the NASA Lewis Research Center's Ceramics Analysis and Reliability Evaluation of Structures (CARES) integrated design programs. CARES/CREEP determines the expected life of a component under creep conditions, and CARES/LIFE predicts the component life due to fast fracture and subcritical crack growth. The previously developed CARES/LIFE program has been used in numerous industrial and Government applications.

  19. Synthesis of aluminum-based scandium-yttrium master alloys

    NASA Astrophysics Data System (ADS)

    Bazhin, V. Yu.; Kosov, Ya. I.; Lobacheva, O. L.; Dzhevaga, N. V.

    2015-07-01

    The preparation technology for an Al-2% Sc-0.5% Y master alloy using aluminum-manganese alloys has been developed and tested. The microstructure of the prepared master alloy is studied and the compositions of intermetallics is determined. The efficient technological parameters of the synthesis are determined. It is shown that varying the compositions of starting reagents and alloying additions and optimizing the process conditions (temperature, mixing, etc.) allow us to forecast the manufacturing and operating characteristics of aluminum-based master alloys. Joint additions of scandium and yttrium oxides to a charge favor a substantial decrease in the grain size of the formed intermetallics; this effect appears to the utmost in the case of microallying with yttrium up to 0.5 wt %.

  20. Metal-ceramic joint assembly

    DOEpatents

    Li, Jian

    2002-01-01

    A metal-ceramic joint assembly in which a brazing alloy is situated between metallic and ceramic members. The metallic member is either an aluminum-containing stainless steel, a high chromium-content ferritic stainless steel or an iron nickel alloy with a corrosion protection coating. The brazing alloy, in turn, is either an Au-based or Ni-based alloy with a brazing temperature in the range of 9500 to 1200.degree. C.

  1. Refractory Oxidative-Resistant Ceramic Carbon Insulation

    NASA Technical Reports Server (NTRS)

    Leiser, Daniel B. (Inventor); Hsu, Ming-Ta S. (Inventor); Chen, Timothy S. (Inventor)

    2001-01-01

    High-temperature, lightweight, ceramic carbon insulation is prepared by coating or impregnating a porous carbon substrate with a siloxane gel derived from the reaction of an organodialkoxy silane and an organotrialkoxy silane in an acid or base medium in the presence of the carbon substrate. The siloxane gel is subsequently dried on the carbon substrate to form a ceramic carbon precursor. The carbon precursor is pyrolyzed, in an inert atmosphere, to form the ceramic insulation containing carbon, silicon, and oxygen. The carbon insulation is characterized as a porous, fibrous, carbon ceramic tile which is particularly useful as lightweight tiles for spacecraft.

  2. Emerging Applications of Ceramic and Metal Matrix Composites

    NASA Astrophysics Data System (ADS)

    Krishnamoorthy, Divya; Ramolina, Dheeyana; Sandou, Sherleena

    2012-07-01

    Almost 500 papers were presented during the 43 sessions of the 27th Annual Cocoa Beach Conference & Exposition on Advanced Ceramics & Composites, which was organized by the Engineering Ceramics Division of the American Ceramic Society and sponsored by several federal agencies: NASA Glenn Research Center, the Army Research Office, the Department of Energy, and the Air Force Office of Scientific Research. Many of these papers focused on composites, both ceramic and metal matrix, and discussed mechanical behavior, design, fibers/interfaces, processing, and applications. Potential applications under development include components for armor, nuclear energy, and automobiles. A few of these applications have reached commercialization.

  3. Development of Detonation Flame Sprayed Cu-Base Coatings Containing Large Ceramic Particles

    NASA Astrophysics Data System (ADS)

    Tillmann, Wolfgang; Vogli, Evelina; Nebel, Jan

    2007-12-01

    Metal-matrix composites (MMCs) containing large ceramic particles as superabrasives are typically used for grinding stone, minerals, and concrete. Sintering and brazing are the key manufacturing technologies for grinding tool production. However, restricted geometry flexibility and the absence of repair possibilities for damaged tool surfaces, as well as difficulties of controlling material interfaces, are the main weaknesses of these production processes. Thermal spraying offers the possibility to avoid these restrictions. The research for this paper investigated a fabrication method based on the use of detonation flame spraying technology to bond large superabrasive particles (150-600 μm, needed for grinding minerals and stones) in a metallic matrix. Layer morphology and bonding quality are evaluated with respect to superabrasive material, geometry, spraying, and powder-injection parameters. The influence of process temperature and the possibilities of thermal treatment of MMC layers are analyzed.

  4. Ceramic on ceramic arthroplasty of the hip: new materials confirm appropriate use in young patients.

    PubMed

    Sentuerk, U; von Roth, P; Perka, C

    2016-01-01

    The leading indication for revision total hip arthroplasty (THA) remains aseptic loosening owing to wear. The younger, more active patients currently undergoing THA present unprecedented demands on the bearings. Ceramic-on-ceramic (CoC) bearings have consistently shown the lowest rates of wear. The recent advances, especially involving alumina/zirconia composite ceramic, have led to substantial improvements and good results in vitro. Alumina/zirconia composite ceramics are extremely hard, scratch resistant and biocompatible. They offer a low co-efficient of friction and superior lubrication and lower rates of wear compared with other bearings. The major disadvantage is the risk of fracture of the ceramic. The new composite ceramic has reduced the risk of fracture of the femoral head to 0.002%. The risk of fracture of the liner is slightly higher (0.02%). Assuming that the components are introduced without impingement, CoC bearings have major advantages over other bearings. Owing to the superior hardness, they produce less third body wear and are less vulnerable to intra-operative damage. The improved tribology means that CoC bearings are an excellent choice for young, active patients requiring THA. ©2016 The British Editorial Society of Bone & Joint Surgery.

  5. Cleanability evaluation of ceramic glazes with nanometer far-infrared materials using contact angle measurement.

    PubMed

    Wang, Lijuan; Liang, Jinsheng; Di, Xingfu; Tang, Qingguo

    2014-05-01

    The cleanability of easy-to-clean ceramic glazes doped with nanometer far-infrared materials was compared with that of some high-quality household ceramic glazes from the market. The cleanability was evaluated by the contact angle measurement using a sessile drop method with a Dataphysics OCA-30 contact angle analyzer. The results showed that the difference of contact angles of water on the glazes before soiling and after cleaning could be used as a parameter for evaluating the cleanability of the glazes. The relationship between cleanability and surface properties, such as surface free energy and surface topography, was investigated. The surface free energy of the samples and their components were calculated using van Oss acid-base approach. By measuring advancing and receding contact angles, the contact angle hysteresis of the ceramic glazes due to the surface topography was investigated. It was shown that the cleanability of ceramic glazes containing nanometer far-infrared materials (NFIM) is better than that of household ceramic glazes from market, due to a higher ratio of electron-acceptor parameter to electron-donor parameter, which led to the effect of water hydration as well as better hydrophilic property and increased smoothness. The contact angle measurement not only accurately evaluates the cleanability of the ceramic glazes, but also has a contribution to the study of cleanability theory. Moreover, this method is simple, convenient and less sample-consumption.

  6. Sol-Gel Synthesis and Antioxidant Properties of Yttrium Oxide Nanocrystallites Incorporating P-123.

    PubMed

    Mellado-Vázquez, Rebeca; García-Hernández, Margarita; López-Marure, Arturo; López-Camacho, Perla Yolanda; de Jesús Morales-Ramírez, Ángel; Beltrán-Conde, Hiram Isaac

    2014-09-19

    Yttrium oxide (Y₂O₃) nanocrystallites were synthesized by mean of a sol-gel method using two different precursors. Raw materials used were yttrium nitrate and yttrium chloride, in methanol. In order to promote oxygen vacancies, P-123 poloxamer was incorporated. Synthesized systems were heat-treated at temperatures from 700 °C to 900 °C. Systems at 900 °C were prepared in the presence and absence of P-123 using different molar ratios (P-123:Y = 1:1 and 2:1). Fourier transform infrared spectroscopy (FTIR) results revealed a characteristic absorption band of Y-O vibrations typical of Y₂O₃ matrix. The structural phase was analyzed by X-ray diffraction (XRD), showing the characteristic cubic phase in all systems. The diffraction peak that presented the major intensity corresponded to the sample prepared from yttrium chloride incorporating P-123 in a molar ratio of P-123:Y = 2:1 at 900 °C. Crystallites sizes were determined by Scherrer equation as between 21 nm and 32 nm. Antioxidant properties were estimated by 2,2-diphenyl-1-picrylhydrazyl (DPPH•) assays; the results are discussed.

  7. Catalysis, nanostructure and macroscopic property triangle in bioactive calcium-containing ceramic systems.

    PubMed

    Meiszterics, Anikó; Havancsák, Károly; Sinkó, Katalin

    2013-04-01

    Calcium silicate ceramics are intended for application as long-term implant materials. In the present work, attention was paid to understand the correlations between the nanostructure (aggregate size, crystallinity, porosity) and the macroscopic properties (solubility in water and simulated body fluids, SBF; hardness) varying the chemical composition. Varying the catalyst (from a base to various acids) during the chemical synthesis was shown to significantly impact on the pore size, crystallinity and mechanical properties. The basic catalyst yields the ceramics with the highest mechanical strength. Ammonia used in 1.0 or 10.0 molar ratio results in bulk ceramics with parameters required for a biomedical application, good hardness (180-200 HV) and low solubility (1-3%) in water and in SBF. The fine porosity (~50 nm) and homogeneous amorphous structure induce good mechanical character. Copyright © 2012 Elsevier B.V. All rights reserved.

  8. Development of BEM for ceramic composites

    NASA Technical Reports Server (NTRS)

    Henry, D. P.; Banerjee, P. K.; Dargush, G. F.

    1991-01-01

    It is evident that for proper micromechanical analysis of ceramic composites, one needs to use a numerical method that is capable of idealizing the individual fibers or individual bundles of fibers embedded within a three-dimensional ceramic matrix. The analysis must be able to account for high stress or temperature gradients from diffusion of stress or temperature from the fiber to the ceramic matrix and allow for interaction between the fibers through the ceramic matrix. The analysis must be sophisticated enough to deal with the failure of fibers described by a series of increasingly sophisticated constitutive models. Finally, the analysis must deal with micromechanical modeling of the composite under nonlinear thermal and dynamic loading. This report details progress made towards the development of a boundary element code designed for the micromechanical studies of an advanced ceramic composite. Additional effort has been made in generalizing the implementation to allow the program to be applicable to real problems in the aerospace industry.

  9. Method for molding ceramic powders

    DOEpatents

    Janney, Mark A.

    1990-01-01

    A method for molding ceramic powders comprises forming a slurry mixture including ceramic powder, a dispersant for the metal-containing powder, and a monomer solution. The monomer solution includes at least one multifunctional monomer, a free-radical initiator, and an organic solvent. The slurry mixture is transferred to a mold, and the mold containing the slurry mixture is heated to polymerize and crosslink the monomer and form a firm polymer-solvent gel matrix. The solid product may be removed from the mold and heated to first remove the solvent and subsequently remove the polymer, whereafter the product may be sintered.

  10. Method for molding ceramic powders

    DOEpatents

    Janney, M.A.

    1990-01-16

    A method for molding ceramic powders comprises forming a slurry mixture including ceramic powder, a dispersant for the metal-containing powder, and a monomer solution. The monomer solution includes at least one multifunctional monomer, a free-radical initiator, and an organic solvent. The slurry mixture is transferred to a mold, and the mold containing the slurry mixture is heated to polymerize and crosslink the monomer and form a firm polymer-solvent gel matrix. The solid product may be removed from the mold and heated to first remove the solvent and subsequently remove the polymer, where after the product may be sintered.

  11. High-temperature testing of glass/ceramic matrix composites

    NASA Technical Reports Server (NTRS)

    Mandell, John F.; Grande, Dodd H.; Dannemann, Kathryn A.

    1989-01-01

    Recent advances in ceramic and other high-temperature composites have created a need for test methods that can be used at 1000 C and above. Present test methods usually require adhesively bonded tabs that cannot be used at high temperatures. This paper discusses some of the difficulties with high-temperature test development and describes several promising test methods. Stress-strain data are given for Nicalon ceramic fiber reinforced glass and glass-ceramic matrix composites tested in air at temperatures up to 1000 C.

  12. Fracture strength and fatigue resistance of all-ceramic molar crowns manufactured with CAD/CAM technology.

    PubMed

    Zahran, Mohammed; El-Mowafy, Omar; Tam, Laura; Watson, Philip A; Finer, Yoav

    2008-07-01

    All-ceramic crowns are subject to fracture during function, especially in the posterior area. The use of yttrium-stabilized zirconium-oxide ceramic as a substructure for all-ceramic crowns to improve fracture resistance is unproven. The aim of this study was to compare fracture strength and fatigue resistance of new zirconium-oxide and feldspathic all-ceramic crowns made with computer-aided design/computer-aided manufacturing (CAD/CAM). An ivorine molar was prepared to receive an all-ceramic crown. Using epoxy resin, 40 replication dies were made of the prepared tooth. Twenty feldspathic all-ceramic crowns (Vita Mark II) (VMII) and 20 zirconium-oxide crown copings (In-Ceram YZ) (YZ) were made using CAD/CAM technique (CEREC-3D). The YZ copings were sintered and veneered manually with a fine-particle ceramic (VM9). All crowns were cemented to their respective dies using resin cement (Panavia F 2.0). Ten crowns in each group were subjected to compressive fatigue loading in a universal testing machine (instron). The other ten crowns from each group were loaded to fracture at a crosshead speed of 1 mm/min. Data were statistically analyzed using independent t-test and Fisher's exact test at alpha= 0.05. There was a significant difference between the survival rates of the two materials during the fatigue test (p < 0.001). All VMII crowns survived without any crack formation, while all YZ crowns fractured (40%) or developed cracks (60%). All the YZ crown fractures occurred within the veneering layer during the fatigue test. There was no significant difference in mean fracture load between the two materials (p= 0.268). Mean fracture loads (standard deviation) in N were: 1459 (492) for YZ crowns and 1272 (109) for VMII crowns. The performance of VMII crowns was superior to YZ crowns in the fatigue test. The premature fractures and cracks of the YZ crowns were attributed to weakness in the YZ veneer layer or in the core/veneer bond.

  13. Fractography of glasses and ceramics II

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

    Frechette, V.D.; Varner, J.R.

    1991-01-01

    Topics addressed include finite element stress analysis and crack path prediction of imploding CRT; fractography and fracture mechanics of combustion growth diamond thin films; the fracture behavior of machineable hydroxyapatite; a fractal approach to crack branching (bifurcation) in glass; the fracture of glass-ionomer cements; the effect of quartz particle size on the strength and toughness of whitewares; and a proposed standard practice for fractographic analysis of monolithic advanced ceramics. Also treated are thermal exposure effects on ceramic matrix composites, fractography applied to rock core analysis, fractography of flexurally fractured glass rods, the fractographic determination of K(IC) and effects of microstructuralmore » effects in ceramics.« less

  14. Protective coating for ceramic materials

    NASA Technical Reports Server (NTRS)

    Kourtides, Demetrius A. (Inventor); Churchward, Rex A. (Inventor); Lowe, David M. (Inventor)

    1994-01-01

    A protective coating for ceramic materials such as those made of silicon carbide, aluminum oxide, zirconium oxide, aluminoborosilicate and silicon dioxide, and a thermal control structure comprising a ceramic material having coated thereon the protective coating. The protective coating contains, in admixture, silicon dioxide powder, colloidal silicon dioxide, water, and one or more emittance agents selected from silicon tetraboride, silicon hexaboride, silicon carbide, molybdenum disilicide, tungsten disilicide and zirconium diboride. In another aspect, the protective coating is coated on a flexible ceramic fabric which is the outer cover of a composite insulation. In yet another aspect, a metallic foil is bonded to the outer surface of a ceramic fabric outer cover of a composite insulation via the protective coating. A primary application of this invention is as a protective coating for ceramic materials used in a heat shield for space vehicles subjected to very high aero-convective heating environments.

  15. Evaluation Of Shielding Efficacy Of A Ferrite Containing Ceramic Material

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

    Verst, C.

    2015-10-12

    The shielding evaluation of the ferrite based Mitsuishi ceramic material has produced for several radiation sources and possible shielding sizes comparative dose attenuation measurements and simulated projections. High resolution gamma spectroscopy provided uncollided and scattered photon spectra at three energies, confirming theoretical estimates of the ceramic’s mass attenuation coefficient, μ/ρ. High level irradiation experiments were performed using Co-60, Cs-137, and Cf-252 sources to measure penetrating dose rates through steel, lead, concrete, and the provided ceramic slabs. The results were used to validate the radiation transport code MCNP6 which was then used to generate dose rate attenuation curves as a functionmore » of shielding material, thickness, and mass for photons and neutrons ranging in energy from 200 keV to 2 MeV.« less

  16. Ceramic fibers from Si-B-C polymer precursors

    NASA Technical Reports Server (NTRS)

    Riccitiello, S. R.; Hsu, M. S.; Chen, T. S.

    1993-01-01

    Non-oxide ceramics such as silicon carbide (SiC), silicon nitride (Si3N4), and silicon borides (SiB4, SiB6) have thermal stability, oxidation resistance, hardness, and varied electrical properties. All these materials can be prepared in a fiber form from a suitable polymer precursor. The above mentioned fibers, when tested over a temperature range from 25 to 1400 C, experience degradation at elevated temperatures. Past work in ceramic materials has shown that the strength of ceramics containing both carbides and borides is sustained at elevated temperatures, with minimum oxidation. The work presented here describes the formation of ceramic fibers containing both elements, boron and silicon, prepared via the polymer precursor route previously reported by the authors, and discusses the fiber mechanical properties that are retained over the temperature range studied.

  17. Making Ceramic Cameras

    ERIC Educational Resources Information Center

    Squibb, Matt

    2009-01-01

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

  18. Preparation, Properties, and Development of Calcium Lanthanum Sulfide as an 8- to 12-micrometer Transmitting Ceramic

    DTIC Science & Technology

    1989-09-01

    Advanced Optical Ceramics Phase "O," by S. Musikant , R. A. Tanzilli, R. J. Charles, G. A. Slack, W. White, and R. M. Cannon. Philadelphia, Penna...1977-February 15, 1978, GE Document No. 78SDR2195.) 2. -----.- Advanced Optical Ceramics, Phase II, by S. Musikant , R. M. Cannon, Jr., C. E. Dulka, J...Document DIN:80SDR2172.) 3. - .....- Advanced Optical Ceramics, Phase I, by S. Musikant , R. M. Cannon, Jr., C. E. Dulka, A. Gatti, J. J. Gebhardt, W. A

  19. A Viscoplastic Constitutive Theory for Monolithic Ceramic Materials. Series 1

    NASA Technical Reports Server (NTRS)

    Janosik, Lesley A.; Duffy, Stephen F.

    1997-01-01

    With increasing use of ceramic materials in high temperature structural applications such as advanced heat engine components, the need arises to accurately predict thermomechanical behavior. This paper, which is the first of two in a series, will focus on inelastic deformation behavior associated with these service conditions by providing an overview of a viscoplastic constitutive model that accounts for time-dependent hereditary material deformation (e.g., creep, stress relaxation, etc.) in monolithic structural ceramics. Early work in the field of metal plasticity indicated that inelastic deformations are essentially unaffected by hydrostatic stress. This is not the case, however, for ceramic-based material systems, unless the ceramic is fully dense. The theory presented here allows for fully dense material behavior as a limiting case. In addition, ceramic materials exhibit different time-dependent behavior in tension and compression. Thus, inelastic deformation models for ceramics must be constructed in a fashion that admits both sensitivity to hydrostatic stress and differing behavior in tension and compression. A number of constitutive theories for materials that exhibit sensitivity to the hydrostatic component of stress have been proposed that characterize deformation using time-independent classical plasticity as a foundation. However, none of these theories allow different behavior in tension and compression. In addition, these theories are somewhat lacking in that they are unable to capture creep, relaxation, and rate-sensitive phenomena exhibited by ceramic materials at high temperature. When subjected to elevated service temperatures, ceramic materials exhibit complex thermomechanical behavior that is inherently time-dependent, and hereditary in the sense that current behavior depends not only on current conditions, but also on thermo-mechanical history. The objective of this work is to present the formulation of a macroscopic continuum theory that

  20. The Influence of Yttrium on High Temperature Oxidation of Valve Steels

    NASA Astrophysics Data System (ADS)

    Grzesik, Z.; Migdalska, M.; Mrowec, S.

    2015-04-01

    The influence of small amounts of yttrium, electrochemically deposited on the surface of four steels utilized in the production of valves in car engines, on the protective properties of the oxide scale and its adherence to the surface of the oxidized materials has been studied under isothermal and thermal cycle conditions. Oxidation measurements have been carried out at 1173 K. It has been found that yttrium addition improves considerably the scale adherence to the substrate surface, increasing thereby corrosion resistance of the studied materials.

  1. Role of laser beam radiance in different ceramic processing: A two wavelengths comparison

    NASA Astrophysics Data System (ADS)

    Shukla, Pratik; Lawrence, Jonathan

    2013-12-01

    Effects of laser beam radiance (brightness) of the fibre and the Nd3+:YAG laser were investigated during surface engineering of the ZrO2 and Si3N4 advanced ceramics with respect to dimensional size and microstructure of both of the advanced ceramics. Using identical process parameters, the effects of radiance of both the Nd3+:YAG laser and a fibre laser were compared thereon the two selected advanced ceramics. Both the lasers showed differences in each of the ceramics employed in relation to the microstructure and grain size as well as the dimensional size of the laser engineered tracks-notwithstanding the use of identical process parameters namely spot size; laser power; traverse speed; Gaussian beam modes; gas flow rate and gas composition as well the wavelengths. From this it was evident that the difference in the laser beam radiance between the two lasers would have had much to do with this effect. The high radiance fibre laser produced larger power per unit area in steradian when compared to the lower radiance of the Nd3+:YAG laser. This characteristically produced larger surface tracks through higher interaction temperature at the laser-ceramic interface. This in turn generated bigger melt-zones and different cooling rates which then led to the change in the microstructure of both the Si3N4 and ZrO2 advance ceramics. Owing to this, it was indicative that lasers with high radiance would result in much cheaper and cost effective laser assisted surface engineering processes, since lower laser power, faster traverse speeds, larger spot sizes could be used in comparison to lasers with lower radiance which require much slower traverse speed, higher power levels and finer spot sizes to induce the same effect thereon materials such as the advanced ceramics.

  2. Engulfment of ceramic particles by fibroblasts does not alter cell behavior.

    PubMed

    Faye, Pierre-Antoine; Roualdes, Olivier; Rossignol, Fabrice; Hartmann, Daniel Jean; Desmoulière, Alexis

    2017-02-17

    Despite many studies, the impact of ceramic particles on cell behavior remains unclear. The aim of the present study was to investigate the effects of nano-sized ceramic particles on fibroblastic cells. Fibroblasts (dermal fibroblasts freshly isolated from skin samples and WI26 fibroblastic cells) were cultured in a monolayer in the presence of alumina or cerium-zirconia particles (≈50 nm diameter) at two concentrations (100 or 500 μg ml -1 ). Fluorescent alumina particles were also used. The following properties were analyzed: cell morphology, cytoplasmic ceramic incorporation (using confocal and transmission electron microscopy) and migration (using a silicon insert). Sedimentation field-flow fractionation (SdFFF) was also used to evaluate the rate of incorporation of ceramic particles into the cells. Finally, after treatment with various concentrations of ceramic particles, fibroblasts were also included in a collagen type I lattice constituting a dermal equivalent (DE), and the collagen lattice retraction and cell proliferation were evaluated. In monolayer conditions, the presence of both alumina and cerium-zirconia ceramic particles did not cause any deleterious effects on cultured cells (dermal fibroblast and WI26 cells) and cell fate was not affected in any way by the presence of ceramic particles in the cytoplasm. Confocal (using fluorescent alumina particles) and electron microscopy (using both alumina and cerium-zirconia particles) showed that ceramic particles were internalized in the WI26 cells. Using fluorescent membrane labeling and fluorescent alumina particles, a membrane was observed around the particle-containing vesicles present in the cytoplasm. Electron microscopy on WI26 cells showed the presence of a classical bilayer membrane around the ceramic particles. Interestingly, SdFFF confirmed that some dermal fibroblasts contained many alumina ceramic particles while others contained very few; in WI26 cells, the uptake of alumina ceramic was

  3. Effect of Er:YAG Laser and Sandblasting in Recycling of Ceramic Brackets.

    PubMed

    Yassaei, Soghra; Aghili, Hossein; Hosseinzadeh Firouzabadi, Azadeh; Meshkani, Hamidreza

    2017-01-01

    Introduction: This study was performed to determine the shear bond strength of rebonded mechanically retentive ceramic brackets after recycling with Erbium-Doped Yttrium Aluminum Garnet (Er:YAG) laser or sandblasting. Methods: Twenty-eight debonded ceramic brackets plus 14 intact new ceramic brackets were used in this study. Debonded brackets were randomly divided into 2 groups of 14. One group was treated by Er:YAG laser and the other with sandblasting. All the specimens were randomly bonded to 42 intact human upper premolars. The shear bond strength of all specimens was determined with a universal testing machine at a crosshead speed of 0.5 mm/min until bond failure occurred. The recycled bracket base surfaces were observed under a scanning electron microscope (SEM). Analysis of variance (ANOVA) and Tukey tests were used to compare the shear bond strength of the 3 groups. Fisher exact test was used to evaluate the differences in adhesive remnant index (ARI) scores. Results: The highest bond strength belonged to brackets recycled by Sandblasting (16.83 MPa). There was no significant difference between the shear bond strength of laser and control groups. SEM photographs showed differences in 2 recycling methods. The laser recycled bracket appeared to have as well-cleaned base as the new bracket. Although the sandblasted bracket photographs showed no remnant adhesives, remarkable micro-roughening of the base of the bracket was apparent. Conclusion: According to the results of this study, both Er:YAG laser and sandblasting were efficient to mechanically recondition retentive ceramic brackets. Also, Er:YAG laser did not change the design of bracket base while removing the remnant adhesives which might encourage its application in clinical practice.

  4. Effect of Er:YAG Laser and Sandblasting in Recycling of Ceramic Brackets

    PubMed Central

    Yassaei, Soghra; Aghili, Hossein; Hosseinzadeh Firouzabadi, Azadeh; Meshkani, Hamidreza

    2017-01-01

    Introduction: This study was performed to determine the shear bond strength of rebonded mechanically retentive ceramic brackets after recycling with Erbium-Doped Yttrium Aluminum Garnet (Er:YAG) laser or sandblasting. Methods: Twenty-eight debonded ceramic brackets plus 14 intact new ceramic brackets were used in this study. Debonded brackets were randomly divided into 2 groups of 14. One group was treated by Er:YAG laser and the other with sandblasting. All the specimens were randomly bonded to 42 intact human upper premolars. The shear bond strength of all specimens was determined with a universal testing machine at a crosshead speed of 0.5 mm/min until bond failure occurred. The recycled bracket base surfaces were observed under a scanning electron microscope (SEM). Analysis of variance (ANOVA) and Tukey tests were used to compare the shear bond strength of the 3 groups. Fisher exact test was used to evaluate the differences in adhesive remnant index (ARI) scores. Results: The highest bond strength belonged to brackets recycled by Sandblasting (16.83 MPa). There was no significant difference between the shear bond strength of laser and control groups. SEM photographs showed differences in 2 recycling methods. The laser recycled bracket appeared to have as well-cleaned base as the new bracket. Although the sandblasted bracket photographs showed no remnant adhesives, remarkable micro-roughening of the base of the bracket was apparent. Conclusion: According to the results of this study, both Er:YAG laser and sandblasting were efficient to mechanically recondition retentive ceramic brackets. Also, Er:YAG laser did not change the design of bracket base while removing the remnant adhesives which might encourage its application in clinical practice. PMID:28912939

  5. A silica optical fiber doped with yttrium aluminosilicate nanoparticles for supercontinuum generation

    NASA Astrophysics Data System (ADS)

    Cheng, Tonglei; Liao, Meisong; Xue, Xiaojie; Li, Jiang; Gao, Weiqing; Li, Xia; Chen, Danping; Zheng, Shupei; Pan, Yubai; Suzuki, Takenobu; Ohishi, Yasutake

    2016-03-01

    We design and fabricate a silica optical fiber doped with yttrium aluminosilicate (YAS, Y2O3-Al2O3-SiO2) nanoparticles in the core. The optical fiber is drawn directly from a silica tube with YAG (Y3Al5O12) ceramics and silica powders (the molar ratio 1:18) in the core at the temperature of ∼1950 °C. The YAS nanoparticles are formed during the optical fiber drawing process. Supercontinuum (SC) generation in the optical fiber is investigated at different pump wavelength. At the pump wavelength of ∼1750 nm which is in the deep anomalous dispersion region, SC spectrum evolution is mainly due to multiple solitons and dispersive waves (DWs), and three pairs of multiple optical solitons and DWs are observed. When the pump wavelength shifts to ∼1500 nm which is close to the zero-dispersion wavelength (ZDW), flattened SC spectrum with ±7 dB uniformity is obtained at the wavelength region of ∼990-1980 nm, and only one obvious soliton and DW are observed. At the pump wavelength of ∼1100 nm, a narrow SC spectrum from ∼1020 to 1180 nm is obtained in the normal dispersion region due to self-phase modulation (SPM) effect.

  6. Mechanical Properties and Fracture Behaviors of the As-Extruded Mg-5Al-3Ca Alloys Containing Yttrium at Elevated Temperature.

    PubMed

    Son, Hyeon-Taek; Kim, Yong-Ho; Kim, Taek-Soo; Lee, Seong-Hee

    2016-02-01

    Effects of yttrium (Y) addition on mechanical properties and fracture behaviors of the as-extruded Mg-Al-Ca based alloys at elevated temperature were investigated by a tensile test. After hot extrusion, the average grain size was refined by Y addition and eutectic phases were broken down into fine particles. Y addition to Mg-5Al-3Ca based alloy resulted in the improvement of strength and ductility at elevated temperature due to fine grain and suppression of grain growth by formation of thermally stable Al2Y intermetallic compound.

  7. Advanced ceramic coating development for industrial/utility gas turbine applications

    NASA Technical Reports Server (NTRS)

    Andersson, C. A.; Lau, S. K.; Bratton, R. J.; Lee, S. Y.; Rieke, K. L.; Allen, J.; Munson, K. E.

    1982-01-01

    The effects of ceramic coatings on the lifetimes of metal turbine components and on the performance of a utility turbine, as well as of the turbine operational cycle on the ceramic coatings were determined. When operating the turbine under conditions of constant cooling flow, the first row blades run 55K cooler, and as a result, have 10 times the creep rupture life, 10 times the low cycle fatigue life and twice the corrosion life with only slight decreases in both specific power and efficiency. When operating the turbine at constant metal temperature and reduced cooling flow, both specific power and efficiency increases, with no change in component lifetime. The most severe thermal transient of the turbine causes the coating bond stresses to approach 60% of the bond strengths. Ceramic coating failures was studied. Analytic models based on fracture mechanics theories, combined with measured properties quantitatively assessed both single and multiple thermal cycle failures which allowed the prediction of coating lifetime. Qualitative models for corrosion failures are also presented.

  8. Sol-Gel Synthesis and Antioxidant Properties of Yttrium Oxide Nanocrystallites Incorporating P-123

    PubMed Central

    Mellado-Vázquez, Rebeca; García-Hernández, Margarita; López-Marure, Arturo; López-Camacho, Perla Yolanda; Morales-Ramírez, Ángel de Jesús; Beltrán-Conde, Hiram Isaac

    2014-01-01

    Yttrium oxide (Y2O3) nanocrystallites were synthesized by mean of a sol-gel method using two different precursors. Raw materials used were yttrium nitrate and yttrium chloride, in methanol. In order to promote oxygen vacancies, P-123 poloxamer was incorporated. Synthesized systems were heat-treated at temperatures from 700 °C to 900 °C. Systems at 900 °C were prepared in the presence and absence of P-123 using different molar ratios (P-123:Y = 1:1 and 2:1). Fourier transform infrared spectroscopy (FTIR) results revealed a characteristic absorption band of Y–O vibrations typical of Y2O3 matrix. The structural phase was analyzed by X-ray diffraction (XRD), showing the characteristic cubic phase in all systems. The diffraction peak that presented the major intensity corresponded to the sample prepared from yttrium chloride incorporating P-123 in a molar ratio of P-123:Y = 2:1 at 900 °C. Crystallites sizes were determined by Scherrer equation as between 21 nm and 32 nm. Antioxidant properties were estimated by 2,2-diphenyl-1-picrylhydrazyl (DPPH•) assays; the results are discussed. PMID:28788211

  9. Advanced Environmental Barrier Coating Development for SiC-SiC Ceramic Matrix Composite Components

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Harder, Bryan; Hurst, Janet B.; Halbig, Michael Charles; Puleo, Bernadette J.; Costa, Gustavo; Mccue, Terry R.

    2017-01-01

    This presentation reviews the NASA advanced environmental barrier coating (EBC) system development for SiC-SiC Ceramic Matrix Composite (CMC) combustors particularly under the NASA Environmentally Responsible Aviation, Fundamental Aeronautics and Transformative Aeronautics Concepts Programs. The emphases have been placed on the current design challenges of the 2700-3000F capable environmental barrier coatings for low NOX emission combustors for next generation turbine engines by using advanced plasma spray based processes, and the coating processing and integration with SiC-SiC CMCs and component systems. The developments also have included candidate coating composition system designs, degradation mechanisms, performance evaluation and down-selects; the processing optimizations using TriplexPro Air Plasma Spray Low Pressure Plasma Spray (LPPS), Plasma Spray Physical Vapor Deposition and demonstration of EBC-CMC systems. This presentation also highlights the EBC-CMC system temperature capability and durability improvements under the NASA development programs, as demonstrated in the simulated engine high heat flux, combustion environments, in conjunction with high heat flux, mechanical creep and fatigue loading testing conditions.

  10. Process for strengthening aluminum based ceramics and material

    DOEpatents

    Moorhead, Arthur J.; Kim, Hyoun-Ee

    2000-01-01

    A process for strengthening aluminum based ceramics is provided. A gaseous atmosphere consisting essentially of silicon monoxide gas is formed by exposing a source of silicon to an atmosphere consisting essentially of hydrogen and a sufficient amount of water vapor. The aluminum based ceramic is exposed to the gaseous silicon monoxide atmosphere for a period of time and at a temperature sufficient to produce a continuous, stable silicon-containing film on the surface of the aluminum based ceramic that increases the strength of the ceramic.

  11. Y-TZP ceramic processing from coprecipitated powders: a comparative study with three commercial dental ceramics.

    PubMed

    Lazar, Dolores R R; Bottino, Marco C; Ozcan, Mutlu; Valandro, Luiz Felipe; Amaral, Regina; Ussui, Valter; Bressiani, Ana H A

    2008-12-01

    (1) To synthesize 3mol% yttria-stabilized zirconia (3Y-TZP) powders via coprecipitation route, (2) to obtain zirconia ceramic specimens, analyze surface characteristics, and mechanical properties, and (3) to compare the processed material with three reinforced dental ceramics. A coprecipitation route was used to synthesize a 3mol% yttria-stabilized zirconia ceramic processed by uniaxial compaction and pressureless sintering. Commercially available alumina or alumina/zirconia ceramics, namely Procera AllCeram (PA), In-Ceram Zirconia Block (CAZ) and In-Ceram Zirconia (IZ) were chosen for comparison. All specimens (6mmx5mmx5mm) were polished and ultrasonically cleaned. Qualitative phase analysis was performed by XRD and apparent densities were measured on the basis of Archimedes principle. Ceramics were also characterized using SEM, TEM and EDS. The hardness measurements were made employing Vickers hardness test. Fracture toughness (K(IC)) was calculated. Data were analyzed using one-way analysis of variance (ANOVA) and Tukey's test (alpha=0.05). ANOVA revealed that the Vickers hardness (p<0.0001) and fracture toughness (p<0.0001) were affected by the ceramic materials composition. It was confirmed that the PA ceramic was constituted of a rhombohedral alumina matrix, so-called alpha-alumina. Both CAZ and IZ ceramics presented tetragonal zirconia and alpha-alumina mixture of phases. The SEM/EDS analysis confirmed the presence of aluminum in PA ceramic. In the IZ and CAZ ceramics aluminum, zirconium and cerium in grains involved by a second phase containing aluminum, silicon and lanthanum were identified. PA showed significantly higher mean Vickers hardness values (H(V)) (18.4+/-0.5GPa) compared to vitreous CAZ (10.3+/-0.2GPa) and IZ (10.6+/-0.4GPa) ceramics. Experimental Y-TZP showed significantly lower results than that of the other monophased ceramic (PA) (p<0.05) but it showed significantly higher fracture toughness (6.0+/-0.2MPam(1/2)) values when compared to the

  12. Development of structural ceramic components for automobile applications

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

    Kawamoto, H.

    1995-12-01

    Development efforts have been made in automobile technologies on heat engines to improve the power performance, the fuel economy, and so on. It is well recognized that ceramic applications are keys to succeed in such advanced heat engines, because of their good mechanical and thermal properties. This paper discusses present automobile applications of structural ceramic components and the expectations in automobile uses. The strength and reliability of mass-produced components for the engines are described with the manufacturing processes. The future R&D directions are recommended for structural ceramics.

  13. Oxidative toxic stress in workers occupationally exposed to ceramic dust: A study in a ceramic manufacturing industry.

    PubMed

    Shad, Mehri Keshvari; Barkhordari, Abolfaz; Mehrparvar, Amir Houshang; Dehghani, Ali; Ranjbar, Akram; Moghadam, Rashid Heidari

    2016-09-27

    Exposure to compounds used in ceramic industries appears to be associated with induction of oxidative toxic stress. This cross sectional study was undertaken to assess the oxidative toxic stress parameters associated with occupational exposure to ceramic dust. Forty ceramic-exposed workers from a ceramic manufacturing industry and 40 unexposed referent subjects were studied. A questionnaire containing information regarding demographic variables, occupational history, history of any chronic disease, antioxidant consumption, and use of therapeutic drugs was administrated to them. Oxidative toxic stress biomarkers including lipid peroxidation (LPO), total antioxidant power (TAP), levels of total Thiol groups (TTG) and catalase (CAT) activity were measured. Significant increments in blood LPO levels, CAT activity and concomitant lower TAP were observed in ceramic exposed workers in comparison to referent group. No statistically significant difference was noted between the means of TTG levels between the groups. Findings of the study indicate that occupational exposure to ceramic dust induces oxidative toxic stress. Supplementation of workers with antioxidants may have beneficial effects on oxidative damages in ceramic industries.

  14. OXIDATION-RESISTANT COATING ON ARTICLES OF YTTRIUM METAL

    DOEpatents

    Wilder, D.R.; Wirkus, C.D.

    1963-11-01

    A process for protecting yttrium metal from oxidation by applying thereto and firing thereon a liquid suspension of a fritted ground silicate or phosphate glass plus from 5 to 35% by weight of CeO/sub 2/ is presented. (AEC)

  15. Ceramic transactions - Materials processing and design: Grain-boundary-controlled properties of fine ceramics II. Volume 44

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

    Niihara, Koichi; Ishizaki, Kozo; Isotani, Mitsuo

    This volume contains selected papers presented at a workshop by the Japan Fine Ceramics Center, `Materials Processing and Design Through Better Control of Grain Boundaries: Emphasizing Fine Ceramics II,` which was held March 17-19, 1994, in Koda-cho, Aichi, Japan. The focus of the workshop was the application of grain boundary phenomena to materials processing and design. The topics covered included electronic materials, evaluation methods, structural materials, and interfaces. Also included is an illuminating overview of the current status of work on grain boundary assisted materials processing and design, particularly for fine ceramics. The volume`s chapter titles are: Electron Microscopy, Evaluation,more » Grain Boundary Control and Design, Functional Ceramics, Composite Materials, Synthesis and Sintering, and Mechanical Properties.« less

  16. Property Screening and Evaluation of Ceramic Turbine Materials

    DTIC Science & Technology

    1984-04-01

    Unless otherwise indicated, the upper and lower spans were 0.875 and 1.750 in., respectively. For room-temperature tests, a stainless steel fixture...Silicon Nitride High Temperature Properties Silicon Carbide Silicon Ceramics Transformation-Toughened Zirconia Structural Ceramics Mechanical Properties...3ilicon carbide and silicon nitride, that have potential as structural components in"advanced gas turbine engines, were evaluated. Thermal and

  17. Influences of powder granularity on crystallizing characteristics in mica-contained glass ceramic

    NASA Astrophysics Data System (ADS)

    Xu, L. N.; Kong, D. Y.; Tian, Q. B.; Lv, Z. J.

    2017-09-01

    A machinable mica-contained glass ceramic in the SiO2-Al2O3-MgO-F glassy system was prepared by ball milling and hot pressed sintering. Three kinds of powder sizes of base glass were chosen and the effects of the glass powder sizes on the crystallization were explored by x-ray diffraction and scanning electron microscopy techniques. The results indicate that mica crystal as a major phase and KFeSi2O6 and mullite as minor phases are crystallized. Applying pressure at 670°C has little influences on the types of crystal precipitated and the preferential growth of crystal. The powder sizes, however, have obvious effects on the morphology of precipitated mica crystals. In the glass sample with a powder size of d50=16.4 µm, the plate-shaped mica phase is precipitated. As the powder size decrease to 9.9 µm and 3.3 µm, however, the particle-shaped mica is formed instead of the plate-shaped crystals.

  18. Li.sub.2 O-Al.sub.2 O.sub.3 -SiO.sub.2 glass ceramic-aluminum containing austenitic stainless steel composite body and a method of producing the same

    DOEpatents

    Cassidy, Roger T.

    1990-05-01

    The present invention relates to a hermetically sealed Li.sub.2 O-Al.sub.2 O.sub.3 -SiO.sub.2 glass ceramic-aluminum containing stainless steel composite body and a method of producing the body. The composite body includes an oxide interfacial region between the glass ceramic and metal, wherein the interfacial region consists essentially of an Al.sub.2 O.sub.3 layer. The interfacial Al.sub.2 O.sub.3 region includes constituents of both the metal and glass ceramic.

  19. Crystallization of lanthanum and yttrium aluminosilicate glasses

    NASA Astrophysics Data System (ADS)

    Sadiki, Najim; Coutures, Jean Pierre; Fillet, Catherine; Dussossoy, Jean Luc

    2006-01-01

    The crystallization behaviour of aluminosilicate glasses of lanthanum (LAS) and yttrium (YAS) containing 2-8 mol% of Ln 2O 3 (Ln = La or Y), 12-30 mol% of Al 2O 3, and 64-80 mol% of SiO 2 has been studied by DTA, XRD and SEM-EDX analysis. X-ray diffraction results indicate the presence of the mullite phase and La 2Si 2O 7 in the monoclinic high-temperature G form (group space P2 1/c) for the LAS glasses, and mullite y-Y 2Si 2O 7 in the monoclinic structure (group space C2/m) and a small amount of β-Y 2Si 2O 7 in the orthorhombic structure (space group Pna2) for the YAS. For both cases, very little tridymite phase is observed. The results also show that the values of Tg for YAS are higher than those for LAS glasses. The crystallization of LAS glasses is more difficult than that of YAS. For all samples, we observed only one kind of mullite (Al/Si = 3.14).

  20. Ceramics for the advanced automotive gas turbine engine: A look at a single shaft design

    NASA Technical Reports Server (NTRS)

    Nosek, S. M.

    1977-01-01

    The results of a preliminary analysis of a single shaft regenerative design with a single stage radial turbine are presented to show the fuel economy that can be achieved at high turbine inlet temperatures, with this particular advanced design, if the turbine tip speed and regenerator inlet temperature are not limited. The engine size was 100 hp for application to a 3500 lb auto. The fuel economy was analyzed by coupling the engine to the auto through a continuously variable speed-ratio transmission and operating the system at constant turbine inlet temperature over the Composite Driving Cycle. The fuel was gasoline and the analysis was for a 85 F day. With a turbine inlet temperature of 2500 F the fuel economy was 26.2 mpg, an improvement of 18 percent over that of 22.3 mpg with a turbine inlet temperature of 1900 F. The turbine tip speed needed for best economy with the 2500 F engine was 2530 ft/sec. The regenerator temperature was approximately 2200 F at idle. Disk stresses were estimated for one single stage radial turbine and two two-stage radial-axial turbines and compared with maximum allowable stress curves estimated for a current ceramic material. Results show a need for higher Weibull Modulus, higher strength ceramics.

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

    PubMed

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

    2014-01-01

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

  2. Advanced Turbine Technology Applications Project (ATTAP)

    NASA Technical Reports Server (NTRS)

    1994-01-01

    Reports technical effort by AlliedSignal Engines in sixth year of DOE/NASA funded project. Topics include: gas turbine engine design modifications of production APU to incorporate ceramic components; fabrication and processing of silicon nitride blades and nozzles; component and engine testing; and refinement and development of critical ceramics technologies, including: hot corrosion testing and environmental life predictive model; advanced NDE methods for internal flaws in ceramic components; and improved carbon pulverization modeling during impact. ATTAP project is oriented toward developing high-risk technology of ceramic structural component design and fabrication to carry forward to commercial production by 'bridging the gap' between structural ceramics in the laboratory and near-term commercial heat engine application. Current ATTAP project goal is to support accelerated commercialization of advanced, high-temperature engines for hybrid vehicles and other applications. Project objectives are to provide essential and substantial early field experience demonstrating ceramic component reliability and durability in modified, available, gas turbine engine applications; and to scale-up and improve manufacturing processes of ceramic turbine engine components and demonstrate application of these processes in the production environment.

  3. Microstructure and dielectric properties of BaTiO{sub 3} ceramic doped with yttrium, magnesium, gallium and silicon for AC capacitor application

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

    Wang, Min-Jia; Yang, Hui; Zhejiang California International NanoSystems Institute, Hangzhou 310029

    2014-12-15

    Graphical abstract: Core–shell structure can be obtained in BaTiO{sub 3} ceramics co-doped with Y–Mg-Ga-Si. Y-Mg-Ga-Si co-dopant can obviously reduce dielectric loss, improve AC breakdown voltage and flatten temperature dependence of capacitance curve. - Highlights: • Y-Mg-Ga-Si co-doped BaTiO{sub 3} ceramics with core-shell structure were prepared. • Y{sup 3+}, Mg{sup 2+}, and Ga{sup 3+} dissolved in the lattice BaTiO{sub 3} replacing Ba{sup 2+} site or Ti{sup 4+} site. • Y{sup 3+} and Ga{sup 3+} tended to remain close to the grain boundaries as a shell maker. • Y-Mg-Ga-Si co-doped BaTiO{sub 3} ceramics show high AC breakdown voltage and low tanδ. -more » Abstract: The microstructures and dielectric properties of Y-Mg-Ga-Si co-doped barium titanate ceramics were investigated. Y{sup 3+} dissolved in the lattice of BaTiO{sub 3} replacing both Ba{sup 2+} site and Ti{sup 4+} site, and Mg{sup 2+} replaced Ti{sup 4+} site. The replacements of Y{sup 3+} and Mg{sup 2+} inhibit the grain growth, cause tetragonal-to-pseudocubic phase transition, reduce the dielectric loss, and flatten the temperature dependence of capacitance curve. The incorporation of Ga{sup 3+} can improve sintering and increase permittivity. Y{sup 3+} and Ga{sup 3+} tended to remain close to the grain boundaries, and play an important role as a shell maker in the formation of the core–shell structure in the co-doped BaTiO{sub 3} ceramics. Excellent dielectric properties: ϵ{sub r} = ∼2487, tanδ = ∼0.7% (at 1 kHz), ΔC/C{sub 25} < ∼6.56% (from −55 °C to 125 °C) and alternating current breakdown voltage E < ∼4.02 kV/mm can be achieved in the BaTiO{sub 3}–0.02Y{sub 2}O{sub 3}–0.03MgO–0.01Ga{sub 2}O{sub 3}–0.005SiO{sub 2} ceramics sintered at 1380 °C. This material has a potential application in alternating current multilayer ceramic capacitor.« less

  4. Proton trapping in yttrium-doped barium zirconate

    NASA Astrophysics Data System (ADS)

    Yamazaki, Yoshihiro; Blanc, Frédéric; Okuyama, Yuji; Buannic, Lucienne; Lucio-Vega, Juan C.; Grey, Clare P.; Haile, Sossina M.

    2013-07-01

    The environmental benefits of fuel cells have been increasingly appreciated in recent years. Among candidate electrolytes for solid-oxide fuel cells, yttrium-doped barium zirconate has garnered attention because of its high proton conductivity, particularly in the intermediate-temperature region targeted for cost-effective solid-oxide fuel cell operation, and its excellent chemical stability. However, fundamental questions surrounding the defect chemistry and macroscopic proton transport mechanism of this material remain, especially in regard to the possible role of proton trapping. Here we show, through a combined thermogravimetric and a.c. impedance study, that macroscopic proton transport in yttrium-doped barium zirconate is limited by proton-dopant association (proton trapping). Protons must overcome the association energy, 29 kJ mol-1, as well as the general activation energy, 16 kJ mol-1, to achieve long-range transport. Proton nuclear magnetic resonance studies show the presence of two types of proton environment above room temperature, reflecting differences in proton-dopant configurations. This insight motivates efforts to identify suitable alternative dopants with reduced association energies as a route to higher conductivities.

  5. Proton trapping in yttrium-doped barium zirconate.

    PubMed

    Yamazaki, Yoshihiro; Blanc, Frédéric; Okuyama, Yuji; Buannic, Lucienne; Lucio-Vega, Juan C; Grey, Clare P; Haile, Sossina M

    2013-07-01

    The environmental benefits of fuel cells have been increasingly appreciated in recent years. Among candidate electrolytes for solid-oxide fuel cells, yttrium-doped barium zirconate has garnered attention because of its high proton conductivity, particularly in the intermediate-temperature region targeted for cost-effective solid-oxide fuel cell operation, and its excellent chemical stability. However, fundamental questions surrounding the defect chemistry and macroscopic proton transport mechanism of this material remain, especially in regard to the possible role of proton trapping. Here we show, through a combined thermogravimetric and a.c. impedance study, that macroscopic proton transport in yttrium-doped barium zirconate is limited by proton-dopant association (proton trapping). Protons must overcome the association energy, 29 kJ mol(-1), as well as the general activation energy, 16 kJ mol(-1), to achieve long-range transport. Proton nuclear magnetic resonance studies show the presence of two types of proton environment above room temperature, reflecting differences in proton-dopant configurations. This insight motivates efforts to identify suitable alternative dopants with reduced association energies as a route to higher conductivities.

  6. The precursors effects on biomimetic hydroxyapatite ceramic powders.

    PubMed

    Yoruç, Afife Binnaz Hazar; Aydınoğlu, Aysu

    2017-06-01

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

  7. Multiscale Modeling of Ceramic Matrix Composites

    NASA Technical Reports Server (NTRS)

    Bednarcyk, Brett A.; Mital, Subodh K.; Pineda, Evan J.; Arnold, Steven M.

    2015-01-01

    Results of multiscale modeling simulations of the nonlinear response of SiC/SiC ceramic matrix composites are reported, wherein the microstructure of the ceramic matrix is captured. This micro scale architecture, which contains free Si material as well as the SiC ceramic, is responsible for residual stresses that play an important role in the subsequent thermo-mechanical behavior of the SiC/SiC composite. Using the novel Multiscale Generalized Method of Cells recursive micromechanics theory, the microstructure of the matrix, as well as the microstructure of the composite (fiber and matrix) can be captured.

  8. Advanced Ceramic Matrix Composites (CMCs) for High Temperature Applications

    NASA Technical Reports Server (NTRS)

    Singh, M.

    2005-01-01

    Advanced ceramic matrix composites (CMCs) are enabling materials for a number of demanding applications in aerospace, energy, and nuclear industries. In the aerospace systems, these materials are being considered for applications in hot sections of jet engines such as the combustor liner, vanes, nozzle components, nose cones, leading edges of reentry vehicles, and space propulsion components. Applications in the energy and environmental industries include radiant heater tubes, heat exchangers, heat recuperators, gas and diesel particulate filters, and components for land based turbines for power generation. These materials are also being considered for use in the first wall and blanket components of fusion reactors. In the last few years, a number of CMC components have been developed and successfully tested for various aerospace and ground based applications. However, a number of challenges still remain slowing the wide scale implementation of these materials. They include robust fabrication and manufacturing, assembly and integration, coatings, property modeling and life prediction, design codes and databases, repair and refurbishment, and cost. Fabrication of net and complex shape components with high density and tailorable matrix properties is quite expensive, and even then various desirable properties are not achievable. In this presentation, a number of examples of successful CMC component development and testing will be provided. In addition, critical need for robust manufacturing, joining and assembly technologies in successful implementation of these systems will be discussed.

  9. Stable Boron Nitride Interphases for Ceramic Matrix Composites

    NASA Technical Reports Server (NTRS)

    Morscher, Gregory N.

    1999-01-01

    Ceramic matrix composites (CMC's) require strong fibers for good toughness and weak interphases so that cracks which are formed in the matrix debond and deflect around the fibers. If the fibers are strongly bonded to the matrix, CMC's behave like monolithic ceramics (e.g., a ceramic coffee cup), and when subjected to mechanical loads that induce cracking, such CMC's fail catastrophically. Since CMC's are being developed for high temperature corrosive environments such as the combustor liner for advanced High Speed Civil Transport aircraft, the interphases need to be able to withstand the environment when the matrix cracks.

  10. Durability and CMAS Resistance of Advanced Environmental Barrier Coatings Systems for SiC/SiC Ceramic Matrix Composites

    NASA Technical Reports Server (NTRS)

    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.

  11. Mechanosynthesis of A Ferritic ODS (Oxide Dispersion Strengthened) Steel Containing 14% Chromium and Its Characterization

    NASA Astrophysics Data System (ADS)

    Rivai, A. K.; Dimyati, A.; Adi, W. A.

    2017-05-01

    One of the advanced materials for application at high temperatures which is aggressively developed in the world is ODS (Oxide Dispersion strengthened) steel. ODS ferritic steels are one of the candidate materials for future nuclear reactors in the world (Generation IV reactors) because it is able to be used in the reactor above 600 °C. ODS ferritic steels have also been developed for the interconnect material of SOFC (Solid Oxide Fuel Cell) which will be exposed to about 800 °C of temperature. The steel is strengthened by dispersing homogeneously of oxide particles (ceramic) in nano-meter sized in the matrix of the steel. Synthesis of a ferritic ODS steel by dispersion of nano-particles of yttrium oxide (yttria: Y2O3) as the dispersion particles, and containing high-chromium i.e. 14% has been conducted. Synthesis of the ODS steels was done mechanically (mechanosynthesis) using HEM (High Energy ball Milling) technique for 40 and 100 hours. The resulted samples were characterized using SEM-EDS (Scanning Electron Microscope-Energy Dispersive Spectroscope), and XRD (X-ray diffraction) to analyze the microstructure characteristics. The results showed that the crystal grains of the sample with 100 hours milling time was much smaller than the sample with 40 hours milling time, and some amount of alloy was formed during the milling process even for 40 hours milling time. Furthermore, the structure analysis revealed that some amount of iron atom substituted by a slight amount of chromium atom as a solid solution. The quantitative analysis showed that the phase mostly consisted of FeCr solid-solution with the structure was BCC (body-centered cubic).

  12. Thin-Film Ceramic Thermocouples Fabricated and Tested

    NASA Technical Reports Server (NTRS)

    Wrbanek, John D.; Fralick, Gustave C.; Farmer, Serene C.; Sayir, Ali; Gregory, Otto J.; Blaha, Charles A.

    2004-01-01

    The Sensors and Electronics Technology Branch of the NASA Glenn Research Center is developing thin-film-based sensors for surface measurement in propulsion system research. Thin-film sensors do not require special machining of the components on which they are mounted, and they are considerably thinner than wire- or foil-based sensors. One type of sensor being advanced is the thin-film thermocouple, specifically for applications in high-temperature combustion environments. Ceramics are being demonstrated as having the potential to meet the demands of thin-film thermocouples in advanced aerospace environments. The maximum-use temperature of noble metal thin-film thermocouples, 1500 C (2700 F), may not be adequate for components used in the increasingly harsh conditions of advanced aircraft and next-generation launch vehicles. Ceramic-based thermocouples are known for their high stability and robustness at temperatures exceeding 1500 C, but are typically in the form of bulky rods or probes. As part of ASTP, Glenn's Sensors and Electronics Technology Branch is leading an in-house effort to apply ceramics as thin-film thermocouples for extremely high-temperature applications as part of ASTP. Since the purity of the ceramics is crucial for the stability of the thermocouples, Glenn's Ceramics Branch and Case Western Reserve University are developing high-purity ceramic sputtering targets for fabricating high-temperature sensors. Glenn's Microsystems Fabrication Laboratory, supported by the Akima Corporation, is using these targets to fabricate thermocouple samples for testing. The first of the materials used were chromium silicide (CrSi) and tantalum carbide (TaC). These refractory materials are expected to survive temperatures in excess of 1500 C. Preliminary results indicate that the thermoelectric voltage output of a thin-film CrSi versus TaC thermocouple is 15 times that of the standard type R (platinum-rhodium versus platinum) thermocouple, producing 20 mV with a 200

  13. Lightweight Ceramic Composition of Carbon Silicon Oxygen and Boron

    NASA Technical Reports Server (NTRS)

    Leiser, Daniel B. (Inventor); Hsu, Ming-Ta (Inventor); Chen, Timothy S. (Inventor)

    1997-01-01

    Lightweight, monolithic ceramics resistant to oxidation in air at high temperatures are made by impregnating a porous carbon preform with a sol which contains a mixture of tetraethoxysilane, dimethyldiethoxysilane and trimethyl borate. The sol is gelled and dried on the carbon preform to form a ceramic precursor. The precursor is pyrolyzed in an inert atmosphere to form the ceramic which is made of carbon, silicon, oxygen and boron. The carbon of the preform reacts with the dried gel during the pyrolysis to form a component of the resulting ceramic. The ceramic is of the same size, shape and form as the carbon precursor. Thus, using a porous, fibrous carbon precursor, such as a carbon felt, results in a porous, fibrous ceramic. Ceramics of the invention are useful as lightweight tiles for a reentry spacecraft.

  14. The reactive element effect of yttrium and yttrium silicon on high temperature oxidation of NiCrAl coating

    NASA Astrophysics Data System (ADS)

    Ramandhany, S.; Sugiarti, E.; Desiati, R. D.; Martides, E.; Junianto, E.; Prawara, B.; Sukarto, A.; Tjahjono, A.

    2018-03-01

    The microstructure formed on the bond coat affects the oxidation resistance, particularly the formation of a protective oxide layer. The adhesion of bond coat and TGO increased significantly by addition of reactive element. In the present work, the effect of yttrium and yttrium silicon as reactive element (RE) on NiCrAl coating was investigated. The NiCrAl (without RE) and NiCrAlX (X:Y or YSi) bond coating were deposited on Hastelloy C-276 substrate by High Velocity Oxygen Fuel (HVOF) method. Isothermal oxidation was carried out at 1000 °C for 100 hours. The results showed that the addition of RE could prevent the breakaway oxidation. Therefore, the coating with reactive element were more protective against high temperature oxidation. Furthermore, the oxidation rate of NiCrAlY coating was lower than NiCrAlYSi coating with the total mass change was ±2.394 mg/cm2 after 100 hours of oxidation. The thickness of oxide scale was approximately 1.18 μm consisting of duplex oxide scale of spinel NiCr2O4 in outer scale and protective α-Al2O3 in inner scale.

  15. A Study on Factors Affecting the Degradation of Magnesium and a Magnesium-Yttrium Alloy for Biomedical Applications

    PubMed Central

    Johnson, Ian; Liu, Huinan

    2013-01-01

    Controlling degradation of magnesium or its alloys in physiological saline solutions is essential for their potential applications in clinically viable implants. Rapid degradation of magnesium-based materials reduces the mechanical properties of implants prematurely and severely increases alkalinity of the local environment. Therefore, the objective of this study is to investigate the effects of three interactive factors on magnesium degradation, specifically, the addition of yttrium to form a magnesium-yttrium alloy versus pure magnesium, the metallic versus oxide surfaces, and the presence versus absence of physiological salt ions in the immersion solution. In the immersion solution of phosphate buffered saline (PBS), the magnesium-yttrium alloy with metallic surface degraded the slowest, followed by pure magnesium with metallic or oxide surfaces, and the magnesium-yttrium alloy with oxide surface degraded the fastest. However, in deionized (DI) water, the degradation rate showed a different trend. Specifically, pure magnesium with metallic or oxide surfaces degraded the slowest, followed by the magnesium-yttrium alloy with oxide surface, and the magnesium-yttrium alloy with metallic surface degraded the fastest. Interestingly, only magnesium-yttrium alloy with metallic surface degraded slower in PBS than in DI water, while all the other samples degraded faster in PBS than in DI water. Clearly, the results showed that the alloy composition, presence or absence of surface oxide layer, and presence or absence of physiological salt ions in the immersion solution all influenced the degradation rate and mode. Moreover, these three factors showed statistically significant interactions. This study revealed the complex interrelationships among these factors and their respective contributions to degradation for the first time. The results of this study not only improved our understanding of magnesium degradation in physiological environment, but also presented the key

  16. Pilot evaluation of four experimental conditioning treatments to improve the bond strength between resin cement and Y-TZP ceramic.

    PubMed

    Monaco, Carlo; Cardelli, Paolo; Scotti, Roberto; Valandro, Luiz Felipe

    2011-02-01

    This study evaluated the bond strength between resin cement and Y-TZP ceramic (Yttrium-stabilized Tetragonal Zirconia Polycrystalline) submitted to different surface conditionings. Fifty Y-TZP ceramic discs (Ø= 10 mm) were allocated into five groups: Gr1 (control)-no conditioning; Gr2-tribochemical silica coating (30-μm SiO(2)) before sintering; Gr3-air abrasion with 50-μm Al(2)O(3) before sintering; Gr4-air abrasion with 110-μ Al(2)O(3) before sintering; Gr5 - air abrasion with 50-μm Al(2)O(3) after sintering. After specimen preparation, cylinders of composite resin were prepared and immediately cemented onto the ceramic. A shear test was performed. One-way ANOVA indicated a statistically significant difference among the groups (p= 0.0019). The mean shear bond strengths (MPa) were: Gr1 = 4.7 ± 0.8,(b) Gr2 = 4.6 ± 0.9,(b) Gr3 = 6.4 ± 1.0,(a) Gr4 = 6.5 ± 1.8,(a) Gr5 = 6 ± 1.3(ab) (same superscript letter indicates statistical similarity). Adhesive fracture between the ceramic and resin cement was the most common failure. No complete cohesive fracture at the ceramic or composite cylinders was noted. Within the limitations of this study, additional surface treatment with air abrasion before and after sintering provided a significant increase in bond strength. Tribochemical silica coating before sintering was not effective as a surface treatment. © 2011 by The American College of Prosthodontists.

  17. Ceramic regenerator program

    NASA Technical Reports Server (NTRS)

    Franklin, Jerrold E.

    1991-01-01

    The feasibility of fabricating an Air Turbo Ramjet (ATR) regenerator containing intricate hydraulic passages from a ceramic material in order to allow operation with high temperature combustion gas and to reduce weight as compared with metallic materials was demonstrated. Platelet technology, ceramic tape casting, and multilayer ceramic packaging techniques were used in this fabrication of subscale silicon nitride components. Proof-of-concept demonstrations were performed to simulate a methane cooled regenerator for an ATR engine. The regenerator vane was designed to operate at realistic service conditions, i.e., 600 psi in a 3500 R (3040 F), 500 fps combustion gas environment. A total of six regenerators were fabricated and tested. The regenerators were shown to be able to withstand internal pressurization to 1575 psi. They were subjected to testing in 500 fps, 3560 R (3100 F) air/propane combustion products and were operated satisfactorily for an excess of 100 hr and 40 thermal cycles which exceeded 2460 R (2000 F).

  18. Current progress in inorganic artificial biomaterials.

    PubMed

    Li, Zhixia; Kawashita, Masakazu

    2011-09-01

    In this review, recent advances in bioceramics, metallic biomaterials, and their composites are discussed in terms of their material properties and new medical applications. Porous calcium phosphate ceramics have attracted a lot attention as scaffolds for tissue-engineering purposes since the porous structure allows bone ingrowth. The addition of biodegradable polymers like chitosan, gelatin, and collagen have modified the degradability of the ceramics and their mechanical properties. Titanium (Ti) alloys are being developed for the fabrication of medical devices for the replacement of hard tissue such as artificial hip joints, bone plates, and dental implants because they are very reliable from the viewpoint of mechanical performance. Physical treatment such as grooving or setting a spatial gap on the surface of materials is applicable to improve the apatite formation on the Ti alloys. Blood-compatible polymers such as poly(ethylene glycol) have been successfully fixed on the surface of Ti via chemical bonding by an electrodeposition method. New functions have been explored in Ni-free, Co-Cr-Mo alloys and Mg alloys. In addition, yttrium-containing or phosphorus-containing glass microspheres (20-30 μm in diameter) and ferrimagnetic ceramic particles have exhibited great potential to realize minimally invasive treatment of cancer without surgical operation via in situ radiotherapy or hyperthermia of cancer, but it is still a major challenge to clarify the biological reaction between the artificial implants and living body before their application.

  19. COMPOSITION AND METHOD FOR COATING A CERAMIC BODY

    DOEpatents

    Blanchard, M.K.

    1958-11-01

    A method is presented for protecting a beryllium carbide-graphite body. The method consists in providing a ceramic coating which must contain at least one basic oxide component, such as CaO, at least one amphoteric oxide component, such as Al/sub 2/O/sub 3/, and at least one acidic oxide component, such as SiO/ sub 2/. Various specific formulations for this ceramic coating are given and the coating is applied by conventional ceramic techniques.

  20. FATIGUE OF DENTAL CERAMICS

    PubMed Central

    Zhang, Yu; Sailer, Irena; Lawn, Brian R

    2013-01-01

    Objectives Clinical data on survival rates reveal that all-ceramic dental prostheses are susceptible to fracture from repetitive occlusal loading. The objective of this review is to examine the underlying mechanisms of fatigue in current and future dental ceramics. Data/sources The nature of various fatigue modes is elucidated using fracture test data on ceramic layer specimens from the dental and biomechanics literature. Conclusions Failure modes can change over a lifetime, depending on restoration geometry, loading conditions and material properties. Modes that operate in single-cycle loading may be dominated by alternative modes in multi-cycle loading. While post-mortem examination of failed prostheses can determine the sources of certain fractures, the evolution of these fractures en route to failure remains poorly understood. Whereas it is commonly held that loss of load-bearing capacity of dental ceramics in repetitive loading is attributable to chemically-assisted 'slow crack growth' in the presence of water, we demonstrate the existence of more deleterious fatigue mechanisms, mechanical rather than chemical in nature. Neglecting to account for mechanical fatigue can lead to gross overestimates in predicted survival rates. Clinical significance Strategies for prolonging the clinical lifetimes of ceramic restorations are proposed based on a crack-containment philosophy. PMID:24135295

  1. Fatigue of dental ceramics.

    PubMed

    Zhang, Yu; Sailer, Irena; Lawn, Brian R

    2013-12-01

    Clinical data on survival rates reveal that all-ceramic dental prostheses are susceptible to fracture from repetitive occlusal loading. The objective of this review is to examine the underlying mechanisms of fatigue in current and future dental ceramics. The nature of various fatigue modes is elucidated using fracture test data on ceramic layer specimens from the dental and biomechanics literature. Failure modes can change over a lifetime, depending on restoration geometry, loading conditions and material properties. Modes that operate in single-cycle loading may be dominated by alternative modes in multi-cycle loading. While post-mortem examination of failed prostheses can determine the sources of certain fractures, the evolution of these fractures en route to failure remains poorly understood. Whereas it is commonly held that loss of load-bearing capacity of dental ceramics in repetitive loading is attributable to chemically assisted 'slow crack growth' in the presence of water, we demonstrate the existence of more deleterious fatigue mechanisms, mechanical rather than chemical in nature. Neglecting to account for mechanical fatigue can lead to gross overestimates in predicted survival rates. Strategies for prolonging the clinical lifetimes of ceramic restorations are proposed based on a crack-containment philosophy. Copyright © 2013 Elsevier Ltd. All rights reserved.

  2. Reactive Processing of Environment Conscious, Biomorphic Ceramics: A Novel and Eco-friendly Route to Advanced Ceramic

    NASA Technical Reports Server (NTRS)

    Singh, M.

    2002-01-01

    Environment-conscious, biomorphic ceramics (Ecoceramics) are a new class of materials that can be produced with renewable resources (wood) and wood wastes (wood sawdust). These materials have tailorable properties with numerous potential applications. Silicon carbide-based ecoceramics have been fabricated by the infiltration of wood-derived carbonaceous preforms with oxide and silicon based materials. The wood-derived carbonaceous preforms have been shown to be quite useful in producing porous or dense materials with different microstructures and compositions. The microstructure and mechanical properties (flexural strength, fracture toughness, elastic modulus, and compressive strength) of a wide variety of Sic-based ecoceramics have been measured. Ecoceramics have tailorable properties and behave like ceramic materials manufactured by conventional approaches. In this presentation the fabrication approach, microstructure, and thermomechanical properties of a wide variety of Sic-based Ecoceramics will be reported.

  3. Micro-domain controlled anisotropic laser ceramics assisted by rare-earth trivalent

    NASA Astrophysics Data System (ADS)

    Sato, Yoichi; Akiyama, Jun; Taira, Takunori

    2012-01-01

    Principles that enable to synthesize anisotropic laser ceramics have been established. Anisotropic laser ceramics contain micro domains made of anisotropic crystals, and we have invented the novel alignment technology of micro domain structure in laser ceramics assisted by rare-earth trivalent. Our novel process is essentially superior to the traditional electromagnetic processing from the viewpoint of mass production. We discussed the significance of anisotropic laser ceramics, and we also show the result of evaluations to our orientation controlled RE:FAP ceramics.

  4. Treatment of unresectable intrahepatic cholangiocarcinoma with yttrium-90 radioembolization: a systematic review and pooled analysis.

    PubMed

    Al-Adra, D P; Gill, R S; Axford, S J; Shi, X; Kneteman, N; Liau, S-S

    2015-01-01

    Radioembolization with yttrium-90 microspheres offers an alternative treatment option for patients with unresectable intrahepatic cholangiocarcinoma (ICC). However, the rarity and heterogeneity of ICC makes it difficult to draw firm conclusions about treatment efficacy. Therefore, the goal of the current study is to systematically review the existing literature surrounding treatment of unresectable ICCs with yttrium-90 microspheres and provide a comprehensive review of the current experience and clinical outcome of this treatment modality. We performed a comprehensive search of electronic databases for ICC treatment and identified 12 studies with relevant data regarding radioembolization therapy with yttrium-90 microspheres. Based on pooled analysis, the overall weighted median survival was 15.5 months. Tumour response based on radiological studies demonstrated a partial response in 28% and stable disease in 54% of patients at three months. Seven patients were able to be downstaged to surgical resection. The complication profile of radioembolization is similar to that of other intra-arterial treatment modalities. Overall survival of patients with ICC after treatment with yttrium-90 microspheres is higher than historical survival rates and shows similar survival to those patients treated with systemic chemotherapy and/or trans-arterial chemoembolization therapy. Therefore, the use of yttrium-90 microspheres should be considered in the list of available treatment options for ICC. However, future randomized trials comparing systemic chemotherapy, TACE and local radiation will be required to identify the optimal treatment modality for unresectable ICC. Crown Copyright © 2014. Published by Elsevier Ltd. All rights reserved.

  5. Environmental Barrier Coatings for Ceramics and Ceramic Composites

    NASA Technical Reports Server (NTRS)

    Lee, Kang N.; Fox, Dennis; Eldridge, Jeffrey; Robinson, R. Craig; Bansal, Narottam

    2004-01-01

    One key factor that limits the performance of current gas turbine engines is the temperature capability of hot section structural components. Silicon-based ceramics, such as SiC/SiC composites and monolithic Si3N4, are leading candidates to replace superalloy hot section components in the next generation gas turbine engines due to their excellent high temperature properties. A major stumbling block to realizing Si-based ceramic hot section components is the recession of Si-based ceramics in combustion environments due to the volatilization of silica scale by water vapor. An external environmental barrier coating (EBC) is the most promising approach to preventing the recession. Current EBCs are based on silicon, mullite (3A12O3-2SiO2) and BSAS (barium strontium aluminum silicate with celsian structure). Volatility of BSAS, BSAS-silica chemical reaction, and low melting point of silicon limit the durability and temperature capability of current EBCs. Research is underway to develop EBCs with longer life and enhanced temperature capability. Understanding key issues affecting the performance of current EBCs is necessary for successful development of advanced EBCs. These issues include stress, chemical compatibility, adherence, and water vapor stability. Factors that affect stress are thermal expansion mismatch, phase stability, chemical stability, elastic modulus, etc. The current understanding on these issues will be discussed.

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

    NASA Technical Reports Server (NTRS)

    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. Chemoembolic Hepatopulmonary Shunt Reduction to Allow Safe Yttrium-90 Radioembolization Lobectomy of Hepatocellular Carcinoma

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

    Gaba, Ron C., E-mail: rgaba@uic.edu; VanMiddlesworth, Kyle A.

    2012-12-15

    Yttrium-90 ({sup 90}Y) radioembolization represents an emerging transcatheter treatment option for the management of hepatocellular carcinoma (HCC). Elevation of the hepatopulmonary shunt fraction risks nontarget radiation to the lungs and may limit the use of {sup 90}Y therapy in patients with locally advanced disease with vascular invasion, who often demonstrate increased shunting. We present two cases in which patients with HCC and portal vein invasion resulting in elevated hepatopulmonary shunt fractions underwent chemoembolic shunt closure to allow safe {sup 90}Y radioembolization. Both patients demonstrated excellent tumor response and patient survival. On this basis, we propose a role for chemoembolic reductionmore » of the lung shunt fraction before {sup 90}Y radioembolization in patients with extensive tumor-related hepatopulmonary shunting.« less

  8. Photonuclear production of yttrium-88 - A high energy gamma emitter for hydrocarbon extraction applications.

    PubMed

    Dale, Daniel S; Starovoitova, Valeriia N; Forest, Tony A; Oliphant, Emily

    2018-05-05

    The use of fracing has risen over the past decade and revolutionized energy production in the US. However, there is still an impetus for further optimization of the extraction of oil and natural gas from vast shale reservoirs. In this work, we discuss photonuclear production of yttrium-88 as a promising radiotracer for fracing operations. Single neutron knock-out from natural monoisotopic yttrium-89 is an inexpensive process resulting in high activity of 88 Y with minimal impurities. MCNPX simulations were performed to estimate the 88 Y yield. Irradiations of natural yttrium using a 32 MeV electron linac equipped with a tungsten bremsstrahlung converter were done to benchmark the simulations. Activities of 88 Y, 87g Y, and 87m Y were measured and found to be in good agreement with the predictions. Copyright © 2018 Elsevier Ltd. All rights reserved.

  9. Ceramic component for electrodes

    DOEpatents

    Marchant, David D.

    1979-01-01

    A ceramic component suitable for preparing MHD generator electrodes consists of HfO.sub.2 and sufficient Tb.sub.4 O.sub.7 to stabilize at least 60 volume percent of the HfO.sub.2 into the cubic structure. The ceramic component may also contain a small amount of PrO.sub.2, Yb.sub.2 O.sub.3 or a mixture of both to improve stability and electronic conductivity of the electrode. The component is highly resistant to corrosion by molten potassium seed and molten coal slag in the MHD fluid and exhibits both ionic and electronic conductivity.

  10. Overview of NASA Studies on High-Temperature Ceramic Fibers

    NASA Technical Reports Server (NTRS)

    DiCarlo, James A.; Yun, Hee Mann

    2001-01-01

    NASA, DOD, and DOE are currently looking to the NASA UEET Program to develop ceramic matrix composites (CMC) for hot-section components in advanced power and propulsion systems - Success will depend strongly on developing ceramic fibers with a variety of key thermostructural properties, in particular, high as-produced tensile strength and retention of a large fraction of this strength for long times under the anticipated CMC service conditions. - Current UEET approach centers on selecting the optimum fiber type from commercially available fibers since the costs for development of advanced fibers are high and the markets for high-temperature CMC have yet to be established.

  11. Modeling the impact behavior of high strength ceramics. Final report

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

    Rajendran, A.M.

    1993-12-01

    An advanced constitutive model is used to describe the shock and high strain rate behaviors of silicon carbide (SC), boron carbide B4C, and titanium diboride (TiB2) under impact loading conditions. The model's governing equations utilize a set of microphysically-based constitutive relationships to model the deformation and damage processes in a ceramic. The total strain is decomposed into elastic, plastic, and microcracking components. The plastic strain component was calculated using conventional viscoplastic equations. The strain components due to microcracking utilized relationships derived for a penny-shaped crack containing elastic solids. The main features of the model include degradation of strength and stiffnessmore » under both compressive and tensile loading conditions. When loaded above the Hugoniot elastic limit (HEL), the strength is limited by the strain rate dependent strength equation. However, below the HEL, the strength variation with respect to strain rate and pressure is modeled through microcracking relationships assuming no plastic flow. The ceramic model parameters were determined using a set of VISAR data from the plate impact experiments.« less

  12. Influence of nanopowders sedimentation on characteristics of Yb-doped Y2O3 transparent ceramics

    NASA Astrophysics Data System (ADS)

    Aleksandrov, E. O.; Shitov, V. A.; Maksimov, R. N.; Basyrova, L. R.

    2017-09-01

    In this work we report on the effects induced by different conditions of nanopowders sedimentation on the microstructure features and optical properties of ytterbium-doped yttrium oxide (Yb:Y2O3) transparent ceramics sintered at 1780 °C for 20 h under a vacuum. The nanopowder of (Yb0.005Y0.995)2O3 co-doped with 5 at % ZrO2 was synthesized by laser ablation and used as the starting material for the fabrication of ceramics. The obtained nanoparticles were annealed at 1100 °C for 3 h in air in order to transform a metastable monoclinic phase into a main cubic phase. After sedimentation for 24 h in isopropyl alcohol the useful suspension was dried using a rotary evaporator operating at different temperatures and pressures. The use of lower evaporation temperature (37 °C) and higher vacuum level (10 mbar) lead to complete removal of organic species from the nanopowder and promote homogeneous densification of the powder compact. Under optimal treatment conditions the optical transmittance and the average content of the scattering centers were measured to be 77 % at a wavelength of 1080 nm and 0.25 ppm, respectively.

  13. Characterizing the residual glass in a MgO/Al2O3/SiO2/ZrO2/Y2O3 glass-ceramic

    PubMed Central

    Seidel, Sabrina; Patzig, Christian; Wisniewski, Wolfgang; Gawronski, Antje; Hu, Yongfeng; Höche, Thomas; Rüssel, Christian

    2016-01-01

    The non-isochemical crystallization of glasses leads to glass-ceramics in which the chemical composition of the amorphous matrix differs from that of the parent glass. It is challenging to solely analyse the properties of these residual glassy phases because they frequently contain finely dispersed crystals. In this study, the composition of the residual glass matrix after the crystallization of a glass with the mol% composition 50.6 SiO2 · 20.7 MgO · 20.7 Al2O3 · 5.6 ZrO2 · 2.4 Y2O3 is analysed by scanning transmission electron microscopy (STEM) including energy dispersive X-ray analysis (EDXS). A batch of the residual glass with the determined composition is subsequently melted and selected properties are analysed. Furthermore, the crystallization behaviour of this residual glass is studied by X-ray diffraction, scanning electron microscopy including electron backscatter diffraction and STEM-EDXS analyses. The residual glass shows sole surface crystallization of indialite and multiple yttrium silicates while bulk nucleation does not occur. This is in contrast to the crystallization behaviour of the parent glass, in which a predominant bulk nucleation of spinel and ZrO2 is observed. The crystallization of the residual glass probably leads to different crystalline phases when it is in contact to air, rather than when it is enclosed within the microstructure of the parent glass-ceramics. PMID:27734918

  14. Ceramic Nanocomposites from Tailor-Made Preceramic Polymers

    PubMed Central

    Mera, Gabriela; Gallei, Markus; Bernard, Samuel; Ionescu, Emanuel

    2015-01-01

    The present Review addresses current developments related to polymer-derived ceramic nanocomposites (PDC-NCs). Different classes of preceramic polymers are briefly introduced and their conversion into ceramic materials with adjustable phase compositions and microstructures is presented. Emphasis is set on discussing the intimate relationship between the chemistry and structural architecture of the precursor and the structural features and properties of the resulting ceramic nanocomposites. Various structural and functional properties of silicon-containing ceramic nanocomposites as well as different preparative strategies to achieve nano-scaled PDC-NC-based ordered structures are highlighted, based on selected ceramic nanocomposite systems. Furthermore, prospective applications of the PDC-NCs such as high-temperature stable materials for thermal protection systems, membranes for hot gas separation purposes, materials for heterogeneous catalysis, nano-confinement materials for hydrogen storage applications as well as anode materials for secondary ion batteries are introduced and discussed in detail. PMID:28347023

  15. Advanced diesel engine component development program, tasks 4-14

    NASA Astrophysics Data System (ADS)

    Kaushal, Tony S.; Weber, Karen E.

    1994-11-01

    This report summarizes the Advanced Diesel Engine Component Development (ADECD) Program to develop and demonstrate critical technology needed to advance the heavy-duty low heat rejection engine concept. Major development activities reported are the design, analysis, and fabrication of monolithic ceramic components; vapor phase and solid film lubrication; electrohydraulic valve actuation; and high pressure common rail injection. An advanced single cylinder test bed was fabricated as a laboratory tool in studying these advanced technologies. This test bed simulates the reciprocator for a system having no cooling system, turbo compounding, Rankine bottoming cycle, common rail injection, and variable valve actuation to achieve fuel consumption of 160 g/kW-hr (.26 lb/hp-hr). The advanced concepts were successfully integrated into the test engine. All ceramic components met their functional and reliability requirements. The firedeck, cast-in-place ports, valves, valve guides, piston cap, and piston ring were made from silicon nitride. Breakthroughs required to implement a 'ceramic' engine included the fabrication of air-gap cylinder heads, elimination of compression gaskets, machining of ceramic valve seats within the ceramic firedeck, fabrication of cast-in-place ceramic port liners, implementation of vapor phase lubrication, and elimination of the engine coolant system. Silicon nitride valves were successfully developed to meet several production abuse test requirements and incorporated into the test bed with a ceramic valve guide and solid film lubrication. The ADECD cylinder head features ceramic port shields to increase insulation and exhaust energy recovery. The combustion chamber includes a ceramic firedeck and piston cap. The tribological challenge posed by top ring reversal temperatures of 550 C was met through the development of vapor phase lubrication using tricresyl phosphate at the ring-liner interface. A solenoid-controlled, variable valve actuation system

  16. Advanced diesel engine component development program, tasks 4-14

    NASA Technical Reports Server (NTRS)

    Kaushal, Tony S.; Weber, Karen E.

    1994-01-01

    This report summarizes the Advanced Diesel Engine Component Development (ADECD) Program to develop and demonstrate critical technology needed to advance the heavy-duty low heat rejection engine concept. Major development activities reported are the design, analysis, and fabrication of monolithic ceramic components; vapor phase and solid film lubrication; electrohydraulic valve actuation; and high pressure common rail injection. An advanced single cylinder test bed was fabricated as a laboratory tool in studying these advanced technologies. This test bed simulates the reciprocator for a system having no cooling system, turbo compounding, Rankine bottoming cycle, common rail injection, and variable valve actuation to achieve fuel consumption of 160 g/kW-hr (.26 lb/hp-hr). The advanced concepts were successfully integrated into the test engine. All ceramic components met their functional and reliability requirements. The firedeck, cast-in-place ports, valves, valve guides, piston cap, and piston ring were made from silicon nitride. Breakthroughs required to implement a 'ceramic' engine included the fabrication of air-gap cylinder heads, elimination of compression gaskets, machining of ceramic valve seats within the ceramic firedeck, fabrication of cast-in-place ceramic port liners, implementation of vapor phase lubrication, and elimination of the engine coolant system. Silicon nitride valves were successfully developed to meet several production abuse test requirements and incorporated into the test bed with a ceramic valve guide and solid film lubrication. The ADECD cylinder head features ceramic port shields to increase insulation and exhaust energy recovery. The combustion chamber includes a ceramic firedeck and piston cap. The tribological challenge posed by top ring reversal temperatures of 550 C was met through the development of vapor phase lubrication using tricresyl phosphate at the ring-liner interface. A solenoid-controlled, variable valve actuation system

  17. Phonon anharmonicity of monoclinic zirconia and yttrium-stabilized zirconia

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

    Li, Chen W.; Smith, Hillary L.; Lan, Tian

    2015-04-13

    Inelastic neutron scattering measurements on monoclinic zirconia (ZrO 2) and 8 mol% yttrium-stabilized zirconia were performed at temperatures from 300 to 1373 ωK. We reported temperature-dependent phonon densities of states (DOS) and Raman spectra obtained at elevated temperatures. First-principles lattice dynamics calculations with density functional theory gave total and partial phonon DOS curves and mode Grüneisen parameters. These mode Grüneisen parameters were used to predict the experimental temperature dependence of the phonon DOS with partial success. However, substantial anharmonicity was found at elevated temperatures, especially for phonon modes dominated by the motions of oxygen atoms. Yttrium-stabilized zirconia (YSZ) was somewhatmore » more anharmonic and had a broader phonon spectrum at low temperatures, owing in part to defects in its structure. YSZ also has a larger vibrational entropy than monoclinic zirconia.« less

  18. Transparent ceramic garnet scintillator optimization via composition and co-doping for high-energy resolution gamma spectrometers (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Cherepy, Nerine J.; Payne, Stephen A.; Seeley, Zachary M.; Beck, Patrick R.; Swanberg, Erik L.; Hunter, Steven L.

    2016-09-01

    Breakthrough energy resolution, R(662keV) <4%, has been achieved with an oxide scintillator, Cerium-doped Gadolinium Yttrium Gallium Aluminum Garnet, or GYGAG(Ce), by optimizing fabrication conditions. Here we describe the dependence of scintillation light yield and energy resolution on several variables: (1) Stoichiometry, in particular Gd/Y and Ga/Al ratios which modify the bandgap energy, (2) Processing methods, including vacuum vs. oxygen sintering, and (3) Trace co-dopants that influence the formation of Ce4+ and modify the intra-bandgap trap distribution. To learn about how chemical composition influences the scintillation properties of transparent ceramic garnet scintillators, we have measured: scintillation decay component amplitudes; intensity and duration of afterglow; thermoluminescence glow curve peak positions and amplitudes; integrated light yield; light yield non-proportionality, as measured in the Scintillator Light Yield Non-Proportionality Characterization Instrument (SLYNCI); and energy resolution for gamma spectroscopy. Optimized GYGAG(Ce) provides R(662 keV) =3.0%, for 0.05 cm3 size ceramics with Silicon photodiode readout, and R(662 keV) =4.6%, at 2 in3 size with PMT readout.

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

    NASA Technical Reports Server (NTRS)

    Sliney, Harold E.; Dellacorte, Christopher

    1993-01-01

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

  20. Quantifying the Effects of the Influence of a Tungsten Long-rod Projectile into Confined Ceramics at High-velocity Impact

    DTIC Science & Technology

    2008-01-29

    be conducted to demonstrate how the confined, brittle samples behave. The study shows that silicon carbide and boron carbide are the optimal...Exposition on Advanced Ceramics and Composites - 27 JAN to 1 FEB 2008, Daytona Beach, FL, The original document contains color images. 14. ABSTRACT 15...specimens investigated were aluminum nitride, boron carbide, 9606 pyroceram, and silicon carbide. The confining sleeve was modeled with RHA and had a

  1. Development of BEM for ceramic composites

    NASA Technical Reports Server (NTRS)

    Henry, D. P.; Banerjee, P. K.; Dargush, G. F.

    1990-01-01

    Details on the progress made during the first three years of a five-year program towards the development of a boundary element code are presented. This code was designed for the micromechanical studies of advance ceramic composites. Additional effort was made in generalizing the implementation to allow the program to be applicable to real problems in the aerospace industry. The ceramic composite formulations developed were implemented in the three-dimensional boundary element computer code BEST3D. BEST3D was adopted as the base for the ceramic composite program, so that many of the enhanced features of this general purpose boundary element code could by utilized. Some of these facilities include sophisticated numerical integration, the capability of local definition of boundary conditions, and the use of quadratic shape functions for modeling geometry and field variables on the boundary. The multi-region implementation permits a body to be modeled in substructural parts; thus dramatically reducing the cost of the analysis. Furthermore, it allows a body consisting of regions of different ceramic matrices and inserts to be studied.

  2. Characterization of yttrium-rich precipitates in a titanium alloy weld

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

    Kolli, R. Prakash, E-mail: pkolli@umd.edu

    The yttrium-rich (Y-rich) precipitates that form in the fusion zone (FZ) of a Ti–5Al–1Sn–1Zr–1V–0.8Mo (wt.%) alloy, or Ti-5111, gas-tungsten arc welds (GTAW) were characterized. The filler metal was modified by a small concentration of Y in order to refine the microstructure and thus improve the FZ ductility. A high number density of nanoscale Y-rich precipitates were characterized in the weld FZ by atom probe tomography (APT) and scanning transmission electron microscopy (STEM). - Highlights: •A high number density of nanoscale precipitates were observed in the FZ matrix. •The nanoscale precipitates are enriched in yttrium. •Oxygen and sulfur are also presentmore » in the Y-rich precipitates and their interfaces.« less

  3. Use of ceramics in point-focus solar receivers

    NASA Technical Reports Server (NTRS)

    Smoak, R. H.; Kudirka, A. A.

    1981-01-01

    One of the research and development efforts in the Solar Thermal Energy Systems Project at the Jet Propulsion Laboratory has been focused on application of ceramic components for advanced point-focus solar receivers. The impetus for this effort is a need for high efficiency, low cost solar receivers which operate in a temperature regime where use of metal components is impractical. The current status of the work on evaluation of ceramic components at JPL and elsewhere is outlined and areas where lack of knowledge is currently slowing application of ceramics are discussed. Future developments of ceramic processing technology and reliability assurance methodology should open up applications for the point-focus solar concentrator system in fuels and chemicals production, in thermochemical energy transport and storage, in detoxification of hazardous materials and in high temperature process heat as well as for electric power generation.

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

    NASA Technical Reports Server (NTRS)

    Stecura, S.

    1979-01-01

    A cyclic furnace study was conducted between 990 - 280 C and 1095 - 280 C to evaluate the effects of yttrium, chromium, and aluminum concentrations in nickel base alloy bond coatings and also the effect of the bond coating thickness on the performance of yttria-stabilized zirconia thermal barrier coatings. The presence and the concentration of yttrium is very critical. Without yttrium, rapid oxidation of Ni-Al, Ni-Cr, and Ni-Cr-Al bond coatings causes zirconia thermal barrier coatings to fail very rapidly. Concentrations of chrominum and aluminum in Ni-Cr-Al-Y bond coating have a very significant effect on the thermal barrier coating life. This effect, however, is not as great as that due to yttrium. Furthermore, the thickness and the thickness uniformity also have a very significant effect on the life of the thermal barrier system.

  5. Ceramic composites reinforced with modified silicon carbide whiskers

    DOEpatents

    Tiegs, Terry N.; Lindemer, Terrence B.

    1990-01-01

    Silicon carbide whisker-reinforced ceramic composites are fabricated in a highly reproducible manner by beneficating the surfaces of the silicon carbide whiskers prior to their usage in the ceramic composites. The silicon carbide whiskers which contain considerable concentrations of surface oxides and other impurities which interact with the ceramic composite material to form a chemical bond are significantly reduced so that only a relatively weak chemical bond is formed between the whisker and the ceramic material. Thus, when the whiskers interact with a crack propagating into the composite the crack is diverted or deflected along the whisker-matrix interface due to the weak chemical bonding so as to deter the crack propagation through the composite. The depletion of the oxygen-containing compounds and other impurities on the whisker surfaces and near surface region is effected by heat treating the whiskers in a suitable oxygen sparaging atmosphere at elevated temperatures. Additionally, a sedimentation technique may be utilized to remove whiskers which suffer structural and physical anomalies which render them undesirable for use in the composite. Also, a layer of carbon may be provided on the surface of the whiskers to further inhibit chemical bonding of the whiskers to the ceramic composite material.

  6. Biodegradable ceramic-polymer composites for biomedical applications: A review.

    PubMed

    Dziadek, Michal; Stodolak-Zych, Ewa; Cholewa-Kowalska, Katarzyna

    2017-02-01

    The present work focuses on the state-of-the-art of biodegradable ceramic-polymer composites with particular emphasis on influence of various types of ceramic fillers on properties of the composites. First, the general needs to create composite materials for medical applications are briefly introduced. Second, various types of polymeric materials used as matrices of ceramic-containing composites and their properties are reviewed. Third, silica nanocomposites and their material as well as biological characteristics are presented. Fourth, different types of glass fillers including silicate, borate and phosphate glasses and their effect on a number of properties of the composites are described. Fifth, wollastonite as a composite modifier and its effect on composite characteristics are discussed. Sixth, composites containing calcium phosphate ceramics, namely hydroxyapatite, tricalcium phosphate and biphasic calcium phosphate are presented. Finally, general possibilities for control of properties of composite materials are highlighted. Copyright © 2016 Elsevier B.V. All rights reserved.

  7. Ceramic composites for rocket engine turbines

    NASA Technical Reports Server (NTRS)

    Herbell, Thomas P.; Eckel, Andrew J.

    1991-01-01

    The use of ceramic materials in the hot section of the fuel turbopump of advanced reusable rocket engines promises increased performance and payload capability, improved component life and economics, and greater design flexibility. Severe thermal transients present during operation of the Space Shuttle Main Engine (SSME), push metallic components to the limit of their capabilities. Future engine requirements might be even more severe. In phase one of this two-phase program, performance benefits were quantified and continuous fiber reinforced ceramic matrix composite components demonstrated a potential to survive the hostile environment of an advaced rocket engine turbopump.

  8. Fracture resistance measurement of advanced ceramics at elevated-temperatures using Chevron-notched specimens and other novel techniques

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

    Jenkins, M.G.

    1995-12-31

    The quasi-static fracture behavior of advanced ceramics was assessed in the temperature range of 20{degrees} to 1400{degrees}C. Chevron-notched, three-point flexure specimens and a laser-based CMOD measurement systems were used in testing. Types of materials characterized included monolithic ceramics (SiC, Si{sub 3}N{sub 4}, MgAl{sub 2}O{sub 4}), self-reinforced monoliths (acicular-grained Si{sub 3}N{sub 4}, acicular grained mullite), and ceramic matrix composites (SiC whisker/Al{sub 2}O{sub 3} matrix, TiB{sub 2} particulate/SiC matrix, SiC fibre/CVI SiC matrix, Al{sub 2}O{sub 3} fibre/CVI SiC matrix). Fracture resistance behaviour of the materials was quantified as three distinct regimes of the fracture histories. At crack initiation, the apparent fracture toughnessmore » was evaluated as the critical stress intensity factor, K{sub IC}. During stable crack propagation, the crack growth resistance was characterized by the instantaneous strain energy release rate, G{sub R} using a compliance method assuming linear-elastic unloading to calculate the effective crack lengths. At final fracture, the complete fracture process was quantified using the work-of-fracture, WOF, which can be equated to the fracture surface energy for linearelastic materials. Results indicate that the chevron-notched, three-point flexure specimen facilitates the study of fracture behavior in a wide range of brittle and quasi-brittle materials at elevated temperatures. The unique features of the chevron geometry, which are automatic, in-situ crack initiation and inherent stable crack growth, are crucial to the successful evaluation of the fracture tests.« less

  9. Chemistry of electronic ceramic materials. Proceedings of the International Conference on the Chemistry of Electronic Ceramic Materials

    NASA Technical Reports Server (NTRS)

    Davies, P. K.; Roth, R. S.

    1991-01-01

    The conference was held at Jackson Hole, Wyoming from August 17 to 22, 1990, and in an attempt to maximize the development of this rapidly moving, multidisciplinary field, this conference brought together major national and international researchers to bridge the gap between those primarily interested in the pure chemistry of inorganic solids and those interested in the physical and electronic properties of ceramics. With the many major discoveries that have occurred over the last decade, one of the goals of this meeting was to evaluate the current understanding of the chemistry of electronic ceramic materials, and to assess the state of a field that has become one of the most important areas of advanced materials research. The topics covered include: crystal chemistry; dielectric ceramics; low temperature synthesis and characterization; solid state synthesis and characterization; surface chemistry; superconductors; theory and modeling.

  10. [Experimental research on the effect of nanophase ceramics on osteoblasts functions].

    PubMed

    Wen, Bo; Chen, Zhiqing; Jiang, Yinshan; Yang, Zhengwen; Xu, Yongzhong

    2005-06-01

    In order to study the cytocompatibility of nanophase hydroxyapatite ceramic in vitro, we prepared hydroxyapatite by use of the wet chemistry techniques. The grain size of hydroxyapatite of interest to the present study was determined by scanning electron microscopy and atomic force microscopy with image analysis software. Primary culture of osteoblast from rat calvaria was established. Protein content, synthesis of alkaline phosphatase and deposition of calcium-containing mineral by osteoblasts cultured on nanophase hydroxyapatite ceramics and on conventional hydroxyapatite ceramics for 7, 14, 21 and 28 days were examined. The results showed that the average surface grain size of the nanophase and that of the conventional HA compact formulations was 55 (nanophase) and 780 (conventional) nm, respectively. More importantly, compared to the synthesis of alkaline phosphatase and deposition of calcium-containing mineral by osteoblasts cultured on nanophase was significantly greater than that on conventional ceramics after 21 and 28 days. The cytocompatibility was significantly greater on nanophase HA than on conventional formulations of the same ceramic.

  11. Intraprocedural yttrium-90 positron emission tomography/CT for treatment optimization of yttrium-90 radioembolization.

    PubMed

    Bourgeois, Austin C; Chang, Ted T; Bradley, Yong C; Acuff, Shelley N; Pasciak, Alexander S

    2014-02-01

    Radioembolization with yttrium-90 ((90)Y) microspheres relies on delivery of appropriate treatment activity to ensure patient safety and optimize treatment efficacy. We report a case in which (90)Y positron emission tomography (PET)/computed tomography (CT) was performed to optimize treatment planning during a same-day, three-part treatment session. This treatment consisted of (i) an initial (90)Y infusion with a dosage determined using an empiric treatment planning model, (ii) quantitative (90)Y PET/CT imaging, and (iii) a secondary infusion with treatment planning based on quantitative imaging data with the goal of delivering a specific total tumor absorbed dose. © 2014 SIR Published by SIR All rights reserved.

  12. Development of BEM for ceramic composites

    NASA Technical Reports Server (NTRS)

    Banerjee, P. K.; Dargush, G. F.; Henry, D. P.

    1988-01-01

    Progress is summarized in the development of a boundary element code BEST3D, designed for the micromechanical studies of advanced ceramic composites. Additional effort was made in generalizing the implementation to allow the program to be applicable to real problems in the aerospace industry.

  13. Engineering long term clinical success of advanced ceramic prostheses.

    PubMed

    Rekow, Dianne; Thompson, Van P

    2007-01-01

    Biocompatability and, in some applications, esthetics make all-ceramic prostheses compelling choices but despite significant improvements in materials properties and toughening mechanisms, these still have significant failure rates. Factors that contribute to the degradation in strength and survival include material selection and prosthesis design which set the upper limit for performance. However, fabrication operations introduce damage that can be exacerbated by environmental conditions and clinical function. Using all-ceramic dental crowns as an example, experimentally derived models provide insight into the relationships between materials properties and initial critical loads to failure. Analysis of fabrication operations suggests strategies to minimize damage. Environmental conditions can create viscoplastic flow of supporting components which can contribute additional stress within the prosthesis. Fatigue is a particularly challenging problem, not only providing the energy to propagate existing damage but, when combined with the wet environment, can create new damage modes. While much is known, the influence of these new damage modes has not been completely elucidated. The role of complex prosthesis geometry and its interaction with other factors on damage initiation and propagation has yet to be well characterized.

  14. How Do You Measure That Ceramic Property?

    NASA Technical Reports Server (NTRS)

    Salem, Jonathan; Helfinstine, John; Quinn, George; Gonczy, Stephen

    2011-01-01

    By using the dozens of consensus test standards and practices developed by the Advanced Ceramics Committee of ASTM, C-28, the measurement of mechanical, physical, thermal, and performance properties can be properly performed. The what, how, how not, and why are clearly illustrated for beginning as well as experienced testers. Using these standards will provide accurate, reliable, and complete data for rigorous comparisons with other test results. The C-28 Committee has involved academics, and producers, and users of ceramics to write and continually update more than 45 standards since the committee's inception in 1986.

  15. Boron-containing organosilane polymers and ceramic materials thereof

    NASA Technical Reports Server (NTRS)

    Riccitiello, Salvatore R. (Inventor); Hsu, Ming-Ta S. (Inventor); Chen, Timothy S. (Inventor)

    1989-01-01

    The present invention relates to a polyorgano borosilane ceramic precursor polymer comprising a plurality of repeating units of the formula: (R(sup 1) single bond B)(sub p) being linked together at B by second units of the formula: single bond (R sup 2) single bond (Si single bond R sup 3) single bond (sub q), where R(sup 1) is a lower alkyl, cycloalkyl, phenyl, or (R(sup 2)R(sup 3) single bond Si single bond B single bond)(sub n) and R(sup 2) and R(sup 3) are each independently selected from hydrogen, lower alkyl, vinyl, cycloalkyl, or aryl, n is an integer between 1 and 100; p is an integer between 1 and 100; and q is an integer between 1 and 100. These materials are prepared by combining an organo borohalide of the formula R(sup 4) single bond B single bond (X sup 1) (sub 2) where R(sup 4) is selected from halogen, lower alkyl, cycloalkyl, or aryl, and an organo halosilane of the formula: R(sup 2)(R sup 3)Si(X sup 2)(sub 2) where R(sup 2) and R (sup 3) are each independently selected from lower alkyl, cycloalkyl, or aryl, and X(sup 1) and X(sup 2) are each independently selected from halogen, in an anhydrous aprotic solvent having a boiling point at ambient pressure of not greater than 160 C with in excess of four equivalents of an alkali metal, heating the reaction mixture and recovering the polyorgano borosilane. These silicon boron polymers are useful to generate high-temperature ceramic materials, such as SiC, SiB4, and B4C, upon thermal degradation above 600 C.

  16. Organosilicon Polymers as Precursors for Silicon Containing Ceramics: Recent Developments.

    DTIC Science & Technology

    1987-08-14

    the polymer to a ceramic material, hopefully of the desired composition . In the latter alternative, shrinkage during pyrolysis should not be great...carbon-carbon composite materials. In order to have a useful preceramic polymer . considerations of structure and reactivitv are of paramount importance...process so that on pyrolysis non-volatile, three-dimensional networks (which lead to maximum weight retention) are formed. Thus. preceramic polymer

  17. MCrAlY bond coat with enhanced Yttrium layer

    DOEpatents

    Jablonski, Paul D; Hawk, Jeffrey A

    2015-04-21

    One or more embodiments relates to an MCrAlY bond coat comprising an MCrAlY layer in contact with a Y--Al.sub.2O.sub.3 layer. The MCrAlY layer is comprised of a .gamma.-M solid solution, a .beta.-MAl intermetallic phase, and Y-type intermetallics. The Y--Al.sub.2O.sub.3 layer is comprised of Yttrium atoms coordinated with oxygen atoms comprising the Al.sub.2O.sub.3 lattice. Both the MCrAlY layer and the Y--Al.sub.2O.sub.3 layer have a substantial absence of Y--Al oxides, providing advantage in the maintainability of the Yttrium reservoir within the MCrAlY bulk. The MCrAlY bond coat may be fabricated through application of a Y.sub.2O.sub.3 paste to an MCrAlY material, followed by heating in a non-oxidizing environment.

  18. Environmental durability of ceramics and ceramic composites

    NASA Technical Reports Server (NTRS)

    Fox, Dennis S.

    1992-01-01

    An account is given of the current understanding of the environmental durability of both monolithic ceramics and ceramic-matrix composites, with a view to the prospective development of methods for the characterization, prediction, and improvement of ceramics' environmental durability. Attention is given to the environmental degradation behaviors of SiC, Si3N4, Al2O3, and glass-ceramic matrix compositions. The focus of corrosion prevention in Si-based ceramics such as SiC and Si3N4 is on the high and low sulfur fuel combustion-product effects encountered in heat engine applications of these ceramics; sintering additives and raw material impurities are noted to play a decisive role in ceramics' high temperature environmental response.

  19. Assessments of Fracture Toughness of Monolithic Ceramics-SEPB Versus SEVNB Methods

    NASA Technical Reports Server (NTRS)

    Choi, Sung R.; Gyekenyesi, John P.

    2006-01-01

    Fracture toughness of a total of 13 advanced monolithic ceramics including silicon nitrides, silicon carbide, aluminas, and glass ceramic was determined at ambient temperature by using both single edge precracked beam (SEPB) and single edge v-notched beam (SEVNB) methods. Relatively good agreement in fracture toughness between the two methods was observed for advanced ceramics with flat R-curves; whereas, poor agreement in fracture toughness was seen for materials with rising R-curves. The discrepancy in fracture toughness between the two methods was due to stable crack growth with crack closure forces acting in the wake region of cracks even in SEVNB test specimens. The effect of discrepancy in fracture toughness was analyzed in terms of microstructural feature (grain size and shape), toughening exponent in R-curve, and stable crack growth determined using back-face strain gaging.

  20. Abscopal Effects and Yttrium-90 Radioembolization

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

    Ghodadra, Anish; Bhatt, Sumantha; Camacho, Juan C.

    2016-07-15

    We present the case of an 80-year-old male with squamous cell carcinoma with bilobar hepatic metastases who underwent targeted Yttrium-90 radioembolization of the right hepatic lobe lesion. Subsequently, there was complete regression of the nontargeted, left hepatic lobe lesion. This may represent the first ever reported abscopal effect in radioembolization. The abscopal effect refers to the phenomenon of tumor response in nontargeted sites after targeted radiotherapy. In this article, we briefly review the immune-mediated mechanisms responsible for the abscopal effect.

  1. Isotope shifts from collinear laser spectroscopy of doubly charged yttrium isotopes

    NASA Astrophysics Data System (ADS)

    Vormawah, L. J.; Vilén, M.; Beerwerth, R.; Campbell, P.; Cheal, B.; Dicker, A.; Eronen, T.; Fritzsche, S.; Geldhof, S.; Jokinen, A.; Kelly, S.; Moore, I. D.; Reponen, M.; Rinta-Antila, S.; Stock, S. O.; Voss, A.

    2018-04-01

    Collinear laser spectroscopy has been performed on doubly charged ions of radioactive yttrium in order to study the isotope shifts of the 294.6-nm 5 s 1/2 2S →5 p 1/2 2P line. The potential of such an alkali-metal-like transition to improve the reliability of atomic-field-shift and mass-shift factor calculations, and hence the extraction of nuclear mean-square radii, is discussed. Production of yttrium ion beams for such studies is available at the IGISOL IV Accelerator Laboratory, Jyväskylä, Finland. This newly recommissioned facility is described here in relation to the on-line study of accelerator-produced short-lived isotopes using collinear laser spectroscopy and application of the technique to doubly charged ions.

  2. The influence of implanted yttrium on the cyclic oxidation behaviour of 304 stainless steel

    NASA Astrophysics Data System (ADS)

    Riffard, F.; Buscail, H.; Caudron, E.; Cueff, R.; Issartel, C.; Perrier, S.

    2006-03-01

    High-temperature alloys are frequently used in power plants, gasification systems, petrochemical industry, combustion processes and in aerospace applications. Depending on the application, materials are subjected to corrosive atmospheres and thermal cycling. In the present work, thermal cycling was carried out in order to study the influence of implanted yttrium on the oxide scale adherence on 304 steel specimens oxidised in air at 1273 K. In situ X-ray diffraction indicates that the oxides formed at 1273 K are different on blank specimens compared to implanted specimens. Glancing angle XRD allows to analyse the oxide scale composition after cooling to room temperature. Experimental results show that yttrium implantation at a nominal dose of 10 17 ions cm -2 does not improve significantly the cyclic oxidation behaviour of the austenitic AISI 304 steel. However, it appears that yttrium implantation remarkably enhance the oxidation resistance during isothermal oxidation. It reduces the transient oxidation stage and the parabolic oxidation rate constant by one order of magnitude.

  3. Slow crack growth versus creep cavity coalescence: Competing failure mechanisms during high-temperature deformation of advanced ceramics

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

    Jenkins, M.G.; Kohles, S.S.; Stevens, T.L.

    1996-12-31

    Duality of failure mechanisms (slow crack growth from pre-existing defects versus cumulative creep damage) is examined in a silicon nitride advanced ceramic recently tested at elevated-temperatures. Static (constant stress over time), dynamic (monotonically-increasing stress over time), and cyclic (fluctuating stress over time) fatigue behaviors were evaluated in tension in ambient air at temperatures of 1150, 1260, and 1370{degrees}C for a hot-isostatically pressed monolithic {beta}-silicon nitride. At 1150{degrees}C, all three types of fatigue results showed the similar failure mechanism of slow crack growth (SCG). At 1260 and 1370{degrees}C the failure mechanism was more complex. Failure under static fatigue was dominated bymore » the accumulation of creep damage via diffusion-controlled cavities. In dynamic fatigue, failure occurred by SCG at high stress rates (>10{sup {minus}2}MPa/s) and by creep damage at low stress rates ({le}10{sup {minus}2} MPa/s). For cyclic fatigue, such rate effects influenced the stress rupture results in which times to failure were greater for dynamic and cyclic fatigue than for static fatigue. Elucidation of failure mechanisms is necessary for accurate prediction of long-term survivability and reliability of structural ceramics.« less

  4. Experimental Techniques for Thermodynamic Measurements of Ceramics

    NASA Technical Reports Server (NTRS)

    Jacobson, Nathan S.; Putnam, Robert L.; Navrotsky, Alexandra

    1999-01-01

    Experimental techniques for thermodynamic measurements on ceramic materials are reviewed. For total molar quantities, calorimetry is used. Total enthalpies are determined with combustion calorimetry or solution calorimetry. Heat capacities and entropies are determined with drop calorimetry, differential thermal methods, and adiabatic calorimetry . Three major techniques for determining partial molar quantities are discussed. These are gas equilibration techniques, Knudsen cell methods, and electrochemical techniques. Throughout this report, issues unique to ceramics are emphasized. Ceramic materials encompass a wide range of stabilities and this must be considered. In general data at high temperatures is required and the need for inert container materials presents a particular challenge.

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

    NASA Technical Reports Server (NTRS)

    Halbig, Michael Charles; Singh, Mrityunjay

    2015-01-01

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

  6. Advanced ceramic matrix composite materials for current and future propulsion technology applications

    NASA Astrophysics Data System (ADS)

    Schmidt, S.; Beyer, S.; Knabe, H.; Immich, H.; Meistring, R.; Gessler, A.

    2004-08-01

    Current rocket engines, due to their method of construction, the materials used and the extreme loads to which they are subjected, feature a limited number of load cycles. Various technology programmes in Europe are concerned, besides developing reliable and rugged, low cost, throwaway equipment, with preparing for future reusable propulsion technologies. One of the key roles for realizing reusable engine components is the use of modern and innovative materials. One of the key technologies which concern various engine manufacturers worldwide is the development of fibre-reinforced ceramics—ceramic matrix composites. The advantages for the developers are obvious—the low specific weight, the high specific strength over a large temperature range, and their great damage tolerance compared to monolithic ceramics make this material class extremely interesting as a construction material. Over the past years, the Astrium company (formerly DASA) has, together with various partners, worked intensively on developing components for hypersonic engines and liquid rocket propulsion systems. In the year 2000, various hot-firing tests with subscale (scale 1:5) and full-scale nozzle extensions were conducted. In this year, a further decisive milestone was achieved in the sector of small thrusters, and long-term tests served to demonstrate the extraordinary stability of the C/SiC material. Besides developing and testing radiation-cooled nozzle components and small-thruster combustion chambers, Astrium worked on the preliminary development of actively cooled structures for future reusable propulsion systems. In order to get one step nearer to this objective, the development of a new fibre composite was commenced within the framework of a regionally sponsored programme. The objective here is to create multidirectional (3D) textile structures combined with a cost-effective infiltration process. Besides material and process development, the project also encompasses the development of

  7. Evaluating the improvement of corrosion residual strength by adding 1.0 wt.% yttrium into an AZ91D magnesium alloy

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

    Wang Qiang; Liu Yaohui, E-mail: liuyaohui2005@yahoo.com; Fang Shijie

    2010-06-15

    The influence of yttrium on the corrosion residual strength of an AZ91D magnesium alloy was investigated detailedly. Scanning electron microscope was employed to analyze the microstructure and the fractography of the studied alloys. The microstructure of AZ91D magnesium alloy is remarkably refined due to the addition of yttrium. The electrochemical potentiodynamic polarization curve of the studied alloy was performed with a CHI 660b electrochemical station in the three-electrode system. The result reveals that yttrium significantly promotes the overall corrosion resistance of AZ91D magnesium alloy by suppressing the cathodic reaction in corrosion process. However, the nucleation and propagation of corrosion pitsmore » on the surface of the 1.0 wt.% Y modified AZ91D magnesium alloy indicate that pitting corrosion still emerges after the addition of yttrium. Furthermore, stress concentration caused by corrosion pits should be responsible for the drop of corrosion residual strength although the addition of yttrium remarkably weakens the effect of stress concentration at the tip of corrosion pits in loading process.« less

  8. Ceramic pressure housing with metal endcaps

    DOEpatents

    Downing, Jr., John P.; DeRoos, Bradley G.; Hackman, Donald J.

    1995-01-01

    A housing for the containment of instrumentation in a high pressure fluid environment that consists of a metallic endcap and ceramic cylinder bonded together. The improvement comprises a structure which results in the improved sealing of said housing as the fluid pressure increases. The cylindrical ceramic tube and endcap are dimensioned such that mechanical failure does not occur when exposed to the desired external operating pressures which includes up to 36,000 feet of water. The housing is designed to withstand the external operating pressures without being subject to mechanical failure or excessive deformation which results in the loss of pressure housing integrity via cracking or deformation of the ceramic tube, deformation of the endcap, or from failure of the bonding agent.

  9. Ceramic pressure housing with metal endcaps

    DOEpatents

    Downing, J.P. Jr.; DeRoos, B.G.; Hackman, D.J.

    1995-06-27

    A housing is disclosed for the containment of instrumentation in a high pressure fluid environment that consists of a metallic endcap and ceramic cylinder bonded together. The improvement comprises a structure which results in the improved sealing of said housing as the fluid pressure increases. The cylindrical ceramic tube and endcap are dimensioned such that mechanical failure does not occur when exposed to the desired external operating pressures which includes up to 36,000 feet of water. The housing is designed to withstand the external operating pressures without being subject to mechanical failure or excessive deformation which results in the loss of pressure housing integrity via cracking or deformation of the ceramic tube, deformation of the endcap, or from failure of the bonding agent. 9 figs.

  10. Recent advancements in transparent ceramics and crystal fibers for high power lasers

    NASA Astrophysics Data System (ADS)

    Kim, W.; Baker, C.; Villalobos, G.; Florea, C.; Gibson, D.; Shaw, L. B.; Bowman, S.; Bayya, S.; Sadowski, B.; Hunt, M.; Askins, C.; Peele, J.; Aggarwal, I. D.; Sanghera, J. S.

    2013-05-01

    In this paper, we present our recent progress in the development of rare-earth (Yb3+ or Ho3+) doped Lu2O3 and Y2O3 sesquioxides for high power solid state lasers. We have fabricated high quality transparent ceramics using nano-powders synthesized by a co-precipitation method. This was accomplished by developments in high purity powder synthesis and low temperature scalable sintering technology developed at NRL. The optical, spectral and morphological properties as well as the lasing performance from our highly transparent ceramics are presented. In the second part of the paper, we discuss our recent research effort in developing cladded-single crystal fibers for high power single frequency fiber lasers has the potential to significantly exceed the capabilities of existing silica fiber based lasers. Single crystal fiber cores with diameters as small as 35μm have been drawn using high purity rare earth doped ceramic or single crystal feed rods by the Laser Heated Pedestal Growth (LHPG) process. Our recent results on the development of suitable claddings on the crystal fiber core are discussed.

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

    PubMed

    Quran, Firas Al; Haj-Ali, Reem

    2012-03-01

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

  12. Ceramics engineering today and tomorrow: Impact on energy

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

    Korwin, M.L.

    1997-12-01

    Ceramic engineering has had a profound impact on the development and use of energy. Perhaps nothing has influenced the growth of human society as much as the presence of energy technology. Today, ceramics are incorporated at all levels of the energy discipline, including dams, electric insulators, capacitors, refractories and fiberglass for home insulation. Tomorrow, leaders are going to expect new ways of harnessing, using and conserving clean and abundant energy. Superconductors and nuclear containment vessels are two developing areas of new ceramic applications. With new environmental regulations, the time of passing-on accepted methods of fabrication will come to an end.more » Ceramic engineers of the future will need to better understand the mechanisms of how materials behave. Through continuous research and joint efforts between different ceramic fields, the future of energy and power, and the technology that it will bring, looks most promising.« less

  13. Manufacturing of PZT-nickel functionally graded piezoelectric ceramics

    NASA Astrophysics Data System (ADS)

    Rubio, Wilfredo M.; Silva, Emílio C. N.; Buiochi, Flávio

    2012-05-01

    A recent approach for designing and manufacturing piezoelectric ceramics consists of using the functionally graded materials (FGM) concept. In this work, nickel (Ni) is used to generate a new PZT-Ni graded ceramic and its dynamic behavior is experimentally explored. The PZT-Ni graded ceramic is manufactured by using the technique of Spark Plasma Sintering (SPS). The ceramic is graded from the top to the bottom surface (along 6 mm of thickness). Specifically, five layers of green powders are sintered: 100 wt% PZT-5A, 90 wt% PZT-5A and 10 wt% Ni, 80 wt% PZT-5A and 20 wt% Ni, 70 wt% PZT-5A and 30 wt% Ni, 60 wt% PZT-5A and 40 wt% Ni. Thus, Ni is used as a second phase, which is added to a PZT-5A matrix, changing its concentration. No manufacturing defects or cracks or exfoliated layers are observed. However, graphite diffusion is observed from the graphite die into the graded ceramic, which does not affect its performance; hence, the ceramic contains enough piezoelectric properties, which allows its polarization and dynamic characterization by determining the impedance curve of the PZT-Ni graded ceramic. The PZT-Ni graded ceramic vibrates at 1.04 MHz, 1.55 MHz and 2.07 MHz.

  14. Radiative properties of ceramic metal-halide high intensity discharge lamps containing additives in argon plasma

    NASA Astrophysics Data System (ADS)

    Cressault, Yann; Teulet, Philippe; Zissis, Georges

    2016-07-01

    The lighting represents a consumption of about 19% of the world electricity production. We are thus searching new effective and environment-friendlier light sources. The ceramic metal-halide high intensity lamps (C-MHL) are one of the options for illuminating very high area. The new C-MHL lamps contain additives species that reduce mercury inside and lead to a richer spectrum in specific spectral intervals, a better colour temperature or colour rendering index. This work is particularly focused on the power radiated by these lamps, estimated using the net emission coefficient, and depending on several additives (calcium, sodium, tungsten, dysprosium, and thallium or strontium iodides). The results show the strong influence of the additives on the power radiated despite of their small quantity in the mixtures and the increase of visible radiation portion in presence of dysprosium.

  15. Novel, Ceramic Membrane System For Hydrogen Separation

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

    Elangovan, S.

    2012-12-31

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

  16. Do sanitary ceramic workers have a worse presentation of chest radiographs or pulmonary function tests than other ceramic workers?

    PubMed

    Tsao, Yu-Chung; Liu, Su-Hsun; Tzeng, I-Shiang; Hsieh, Tsung-Han; Chen, Jau-Yuan; Luo, Jiin-Chyuan John

    2017-03-01

    Silicosis remains the most prevalent occupational disease worldwide. There have been no specific studies focusing on the association between exposure settings at work and the clinical severity in silicosis patients. In this study, we describe and compare the clinical characteristics and silicosis-associated exposure history at work among workers from several types of ceramic production facilities in Taiwan. We reviewed the medical records of 221 patients who were first diagnosed with silicosis at the Occupational Medicine Clinic of Northern Taiwan in 2012. For each patient, we collected data on demographic characteristics, smoking habits, working history, duration of exposure, and years on the first relevant job. We also retrieved clinical reports of the pulmonary function test and the baseline chest radiography used for silicosis staging. As compared to other ceramic workers, sanitary ceramic workers had a worse X-ray type (p=0.044), more advanced age (p<0.001), longer working duration (p=0.029), and a higher proportion of starting the first relevant job prior to the year 1975 (p=0.003). However, after adjusting for age, work duration, and an initial occupational exposure prior to 1975, sanitary ceramic workers showed a comparable risk for worse X-ray findings to other ceramic workers (adjusted odds ratio=1.18, p=0.704). Results of multivariable regression models on individual lung function parameter also suggested comparably impaired lung function tests between sanitary and other ceramic workers (p>0.05). In this study, we found that sanitary ceramic workers were at a similar risk to other ceramic workers for moderate to severe silicosis when older age and longer working duration were accounted for. Copyright © 2016. Published by Elsevier B.V.

  17. Bioactive and inert dental glass-ceramics.

    PubMed

    Montazerian, Maziar; Zanotto, Edgar Dutra

    2017-02-01

    The global market for dental materials is predicted to exceed 10 billion dollars by 2020. The main drivers for this growth are easing the workflow of dentists and increasing the comfort of patients. Therefore, remarkable research projects have been conducted and are currently underway to develop improved or new dental materials with enhanced properties or that can be processed using advanced technologies, such as CAD/CAM or 3D printing. Among these materials, zirconia, glass or polymer-infiltrated ceramics, and glass-ceramics (GCs) are of great importance. Dental glass-ceramics are highly attractive because they are easy to process and have outstanding esthetics, translucency, low thermal conductivity, high strength, chemical durability, biocompatibility, wear resistance, and hardness similar to that of natural teeth, and, in certain cases, these materials are bioactive. In this review article, we divide dental GCs into the following two groups: restorative and bioactive. Most restorative dental glass-ceramics (RDGCs) are inert and biocompatible and are used in the restoration and reconstruction of teeth. Bioactive dental glass-ceramics (BDGCs) display bone-bonding ability and stimulate positive biological reactions at the material/tissue interface. BDGCs are suggested for dentin hypersensitivity treatment, implant coating, bone regeneration and periodontal therapy. Throughout this paper, we elaborate on the history, processing, properties and applications of RDGCs and BDGCs. We also report on selected papers that address promising types of dental glass-ceramics. Finally, we include trends and guidance on relevant open issues and research possibilities. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 619-639, 2017. © 2016 Wiley Periodicals, Inc.

  18. Method For Removing Volatile Components From A Gel-Cast Ceramic Article

    DOEpatents

    Klug, Frederic Joseph; DeCarr, Sylvia Marie

    2004-09-07

    A method of removing substantially all of the volatile component in a green, volatile-containing ceramic article is disclosed. The method comprises freezing the ceramic article; and then subjecting the frozen article to a vacuum for a sufficient time to freeze-dry the article. Frequently, the article is heated while being freeze-dried. Use of this method efficiently reduces the propensity for any warpage of the article. The article is often formed from a ceramic slurry in a gel-casting process. A method for fabricating a ceramic core used in investment casting is also described.

  19. Modeling the Mechanical Behavior of Ceramic Matrix Composite Materials

    NASA Technical Reports Server (NTRS)

    Jordan, William

    1998-01-01

    Ceramic matrix composites are ceramic materials, such as SiC, that have been reinforced by high strength fibers, such as carbon. Designers are interested in using ceramic matrix composites because they have the capability of withstanding significant loads while at relatively high temperatures (in excess of 1,000 C). Ceramic matrix composites retain the ceramic materials ability to withstand high temperatures, but also possess a much greater ductility and toughness. Their high strength and medium toughness is what makes them of so much interest to the aerospace community. This work concentrated on two different tasks. The first task was to do an extensive literature search into the mechanical behavior of ceramic matrix composite materials. This report contains the results of this task. The second task was to use this understanding to help interpret the ceramic matrix composite mechanical test results that had already been obtained by NASA. Since the specific details of these test results are subject to the International Traffic in Arms Regulations (ITAR), they are reported in a separate document (Jordan, 1997).

  20. Method of making a modified ceramic-ceramic composite

    DOEpatents

    Weaver, Billy L.; McLaughlin, Jerry C.; Stinton, David P.

    1995-01-01

    The present invention provides a method of making a shaped ceramic-ceramic composite articles, such as gas-fired radiant heat burner tubes, heat exchangers, flame dispersers, and other furnace elements, having a formed-on ceramic-ceramic composite thereon.

  1. Chemically Derived Dense Alumina-Zirconia Composites for Improved Mechanical and Wear Erosion Properties

    NASA Technical Reports Server (NTRS)

    1998-01-01

    As a result of this funded project high purity Zirconia-Toughened Alumina (ZTA) ceramic powders with and without yttria were produced using metal alkoxide precursors. ZTA ceramic powders with varying volume percents of zirconia were prepared (7, 15, and 22%). Aluminum tri-sec butoxide, zirconium propoxide, and yttrium isopropoxide were the reagents used. Synthesis conditions were varied to control the hydrolysis and the aging conditions for the sol to gel transition. FTIR analysis and rheological characterization were used to follow the structural evolution during the sol to gel transition. The greater extent of hydrolysis and the build-up of structure measured from viscoelastic properties were consistent. Heat treatment was conducted to produce submicron grain fully crystalline ZTA ceramic powders. This improved materials should have enhanced properties such strength, toughness, and wear resistance for advanced structural applications, for example engine components in high technology aerospace applications.

  2. Ceramic Integration Technologies for Aerospace and Energy Systems: Technical Challenges and Opportunities

    NASA Technical Reports Server (NTRS)

    Singh, Mrityunjay

    2007-01-01

    Ceramic integration technology has been recognized as an enabling technology for the implementation of advanced ceramic systems in a number of high-temperature applications in aerospace, power generation, nuclear, chemical, and electronic industries. Various ceramic integration technologies (joining, brazing, attachments, repair, etc.) play a role in fabrication and manufacturing of large and complex shaped parts of various functionalities. However, the development of robust and reliable integrated systems with optimum performance requires the understanding of many thermochemical and thermomechanical factors, particularly for high temperature applications. In this presentation, various challenges and opportunities in design, fabrication, and testing of integrated similar (ceramic-ceramic) and dissimilar (ceramic-metal) material systems will be discussed. Experimental results for bonding and integration of SiC based LDI fuel injector, high conductivity C/C composite based heat rejection system, solid oxide fuel cells system, ultra high temperature ceramics for leading edges, and ceramic composites for thermostructural applications will be presented. Potential opportunities and need for the development of innovative design philosophies, approaches, and integrated system testing under simulated application conditions will also be discussed.

  3. Radiopaque Strontium Fluoroapatite Glass-Ceramics.

    PubMed

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

    2015-01-01

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

  4. Radiopaque Strontium Fluoroapatite Glass-Ceramics

    PubMed Central

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

    2015-01-01

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

  5. Process of producing a ceramic matrix composite article and article formed thereby

    DOEpatents

    Corman, Gregory Scot [Ballston Lake, NY; McGuigan, Henry Charles [Duanesburg, NY; Brun, Milivoj Konstantin [Ballston Lake, NY

    2011-10-25

    A CMC article and process for producing the article to have a layer on its surface that protects a reinforcement material within the article from damage. The method entails providing a body containing a ceramic reinforcement material in a matrix material that contains a precursor of a ceramic matrix material. A fraction of the reinforcement material is present and possibly exposed at a surface of the body. The body surface is then provided with a surface layer formed of a slurry containing a particulate material but lacking the reinforcement material of the body. The body and surface layer are heated to form the article by converting the precursor within the body to form the ceramic matrix material in which the reinforcement material is contained, and by converting the surface layer to form the protective layer that covers any fraction of the reinforcement material exposed at the body surface.

  6. Braze material for joining ceramic to metal and ceramic to ceramic surfaces and joined ceramic to metal and ceramic to ceramic article

    DOEpatents

    Hunt, T.K.; Novak, R.F.

    1991-05-07

    An improved active metal braze filler material is provided in which the coefficient of thermal expansion of the braze filler is more closely matched with that of the ceramic and metal, or two ceramics, to provide ceramic to metal, or ceramic to ceramic, sealed joints and articles which can withstand both high temperatures and repeated thermal cycling without failing. The braze filler material comprises a mixture of a material, preferably in the form of a powder, selected from the group consisting of molybdenum, tungsten, silicon carbide and mixtures thereof, and an active metal filler material selected from the group consisting of alloys or mixtures of nickel and titanium, alloys or mixtures of nickel and zirconium, alloys or mixtures of nickel, titanium, and copper, alloys or mixtures of nickel, titanium, and zirconium, alloys or mixtures of niobium and nickel, alloys or mixtures of niobium and zirconium, alloys or mixtures of niobium and titanium, alloys or mixtures of niobium, titanium, and nickel, alloys or mixtures of niobium, zirconium, and nickel, and alloys or mixtures of niobium, titanium, zirconium, and nickel. The powder component is selected such that its coefficient of thermal expansion will effect the overall coefficient of thermal expansion of the braze material so that it more closely matches the coefficients of thermal expansion of the ceramic and metal parts to be joined. 3 figures.

  7. Braze material for joining ceramic to metal and ceramic to ceramic surfaces and joined ceramic to metal and ceramic to ceramic article

    DOEpatents

    Hunt, Thomas K.; Novak, Robert F.

    1991-01-01

    An improved active metal braze filler material is provided in which the coefficient of thermal expansion of the braze filler is more closely matched with that of the ceramic and metal, or two ceramics, to provide ceramic to metal, or ceramic to ceramic, sealed joints and articles which can withstand both high temperatures and repeated thermal cycling without failing. The braze filler material comprises a mixture of a material, preferably in the form of a powder, selected from the group consisting of molybdenum, tungsten, silicon carbide and mixtures thereof, and an active metal filler material selected from the group consisting of alloys or mixtures of nickel and titanium, alloys or mixtures of nickel and zirconium, alloys or mixtures of nickel, titanium, and copper, alloys or mixtures of nickel, titanium, and zirconium, alloys or mixtures of niobium and nickel, alloys or mixtures of niobium and zirconium, alloys or mixtures of niobium and titanium, alloys or mixtures of niobium, titanium, and nickel, alloys or mixtures of niobium, zirconium, and nickel, and alloys or mixtures of niobium, titanium, zirconium, and nickel. The powder component is selected such that its coefficient of thermal expansion will effect the overall coefficient of thermal expansion of the braze material so that it more closely matches the coefficients of thermal expansion of the ceramic and metal parts to be joined.

  8. Portfolio: Ceramics.

    ERIC Educational Resources Information Center

    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…

  9. Thermal shock resistance ceramic insulator

    DOEpatents

    Morgan, Chester S.; Johnson, William R.

    1980-01-01

    Thermal shock resistant cermet insulators containing 0.1-20 volume % metal present as a dispersed phase. The insulators are prepared by a process comprising the steps of (a) providing a first solid phase mixture of a ceramic powder and a metal precursor; (b) heating the first solid phase mixture above the minimum decomposition temperature of the metal precursor for no longer than 30 minutes and to a temperature sufficiently above the decomposition temperature to cause the selective decomposition of the metal precursor to the metal to provide a second solid phase mixture comprising particles of ceramic having discrete metal particles adhering to their surfaces, said metal particles having a mean diameter no more than 1/2 the mean diameter of the ceramic particles, and (c) densifying the second solid phase mixture to provide a cermet insulator having 0.1-20 volume % metal present as a dispersed phase.

  10. NDE of ceramics and ceramic composites

    NASA Technical Reports Server (NTRS)

    Vary, Alex; Klima, Stanley J.

    1991-01-01

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

  11. Coated ceramic breeder materials

    DOEpatents

    Tam, Shiu-Wing; Johnson, Carl E.

    1987-01-01

    A breeder material for use in a breeder blanket of a nuclear reactor is disclosed. The breeder material comprises a core material of lithium containing ceramic particles which has been coated with a neutron multiplier such as Be or BeO, which coating has a higher thermal conductivity than the core material.

  12. Coated ceramic breeder materials

    DOEpatents

    Tam, Shiu-Wing; Johnson, Carl E.

    1987-04-07

    A breeder material for use in a breeder blanket of a nuclear reactor is disclosed. The breeder material comprises a core material of lithium containing ceramic particles which has been coated with a neutron multiplier such as Be or BeO, which coating has a higher thermal conductivity than the core material.

  13. Dense nanocrystalline yttrium iron garnet films formed at room temperature by aerosol deposition

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

    Johnson, Scooter D., E-mail: scooter.johnson@nrl.navy.mil; Glaser, Evan R.; Cheng, Shu-Fan

    Highlights: • We deposit yttrium iron garnet films at room temperature using aerosol deposition. • Films are 96% of theoretical density for yttrium iron garnet. • We report magnetic and structural properties post-deposition and post-annealing. • Low-temperature annealing decreases the FMR linewidth. • We discuss features of the FMR spectra at each anneal temperature. - Abstract: We have employed aerosol deposition to form polycrystalline yttrium iron garnet (YIG) films on sapphire at room temperature that are 90–96% dense. We characterize the structural and dynamic magnetic properties of the dense films using scanning electron microscopy, X-ray diffraction, and ferromagnetic resonance techniques.more » We find that the as-deposited films are pure single-phase YIG formed of compact polycrystallites ∼20 nm in size. The ferromagnetic resonance mode occurs at 2829 G with a linewidth of 308 G. We perform a series of successive anneals up to 1000 °C on a film to explore heat treatment on the ferromagnetic resonance linewidth. We find the narrowest linewidth of 98 G occurs after a 750 °C anneal.« less

  14. Ceramic Bearings For Gas-Turbine Engines

    NASA Technical Reports Server (NTRS)

    Zaretsky, Erwin V.

    1989-01-01

    Report reviews data from three decades of research on bearings containing rolling elements and possibly other components made of ceramics. Ceramic bearings attractive for use in gas-turbine engines because ceramics generally retain strengths and resistances to corrosion over range of temperatures greater than typical steels used in rolling-element bearings. Text begins with brief description of historical developments in field. Followed by discussion of effects of contact stress on fatigue life of rolling element. Supplemented by figures and tables giving data on fatigue lives of rolling elements made of various materials. Analyzes data on effects of temperature and speed on fatigue lives for several materials and operating conditions. Followed by discussion of related topic of generation of heat in bearings, with consideration of effects of bearing materials, lubrication, speeds, and loads.

  15. Biocompatibility of polymer-infiltrated-ceramic-network (PICN) materials with Human Gingival Fibroblasts (HGFs).

    PubMed

    Grenade, Charlotte; De Pauw-Gillet, Marie-Claire; Gailly, Patrick; Vanheusden, Alain; Mainjot, Amélie

    2016-09-01

    Polymer-infiltrated-ceramic-network (PICN) materials constitute an innovative class of CAD-CAM materials offering promising perspectives in prosthodontics, but no data are available in the literature regarding their biological properties. The objective of the present study was to evaluate the in vitro biocompatibility of PICNs with human gingival fibroblasts (HGFs) in comparison with materials typically used for implant prostheses and abutments. HGF attachment, proliferation and spreading on discs made of PICN, grade V titanium (Ti), yttrium zirconia (Zi), lithium disilicate glass-ceramic (eM) and polytetrafluoroethylene (negative control), were evaluated using a specific insert-based culture system (IBS-R). Sample surface properties were characterized by XPS, contact angle measurement, profilometry and SEM. Ti and Zi gave the best results regarding HGF viability, morphology, number and coverage increase with time in comparison with the negative control, while PICN and eM gave intermediate results, cell spreading being comparable for PICN, Ti, Zi and eM. Despite the presence of polymers and their related hydrophobicity, PICN exhibited comparable results to glass-ceramic materials, which could be explained by the mode of polymerization of the monomers. The results of the present study confirm that the currently employed materials, i.e. Ti and Zi, can be considered to be the gold standard of materials in terms of HGF behavior, while PICN gave intermediate results comparable to eM. The impact of the present in vitro results needs to be further investigated clinically, particularly in the view of the utilization of PICNs for prostheses on bone-level implants. Copyright © 2016 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  16. Artificial organs: recent progress in metals and ceramics.

    PubMed

    Nomura, Naoyuki

    2010-04-01

    The superior properties and novel functions of biomaterials, including metals and ceramics commonly used as implants and medical devices, have been the focus of a number of recent papers. New functions have been explored in metastable beta-Ti alloys, Ni-free Co-Cr-Mo alloys, Mg alloys, and other materials. In addition, porous metals and ceramics with sophisticated structures have been studied as scaffolds for regenerative medicine. In this review, recent advances in bioceramics, metallic biomaterials, and their composites are discussed in terms of their material properties and morphology.

  17. Structure-substitution limit correlation study on Cr{sup 3+} substituted polycrystalline yttrium iron garnet

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

    Modi, K. B.; Saija, K. G.; Sharma, P. U.

    2016-05-06

    Polycrystalline samples of Cr{sup 3+} - substituted yttrium iron garnet (Y{sub 3}Fe{sub 5}O{sub 12}) system with general chemical formula, Y{sub 3}Fe{sub 5-x}Cr{sub x}O{sub 12}, x = 0.0, 0.2, 0.4 and 0.6 were synthesized by double sintering ceramic technique and characterized by X-ray powder diffractometry. The Rietveld fitted X-ray diffraction patterns analysis revealed mono phase formation for x = 0.0 - 0.4 compositions while x = 0.6 composition possesses mixed phase character. The observed substitution limit has been discussed in the light of ionic size of substituent, electrostatic energy, electronic configuration and synthesis parameters. These observations strongly suggest that the electronicmore » configuration of Cr{sup 3+}, which is favorable to the formation of d2sp3 (octahedral) type bonds, must be important. In the case of Cr{sup 3+}, the substitution does not appear to proceed well for x much greater than 0.5, this limitation probably is a consequence of the strong preference of a smaller ion Cr{sup 3+}, for a larger octahedral site which quickly leads to a condition not comparable with the requirement of the structure. The distribution of cations, mean ionic radii and theoretical lattice constant values have been determined.« less

  18. Development of Thin Film Ceramic Thermocouples for High Temperature Environments

    NASA Technical Reports Server (NTRS)

    Wrbanek, John D.; Fralick, Gustave C.; Farmer, Serene C.; Sayir, Ali; Blaha, Charles A.; Gonzalez, Jose M.

    2004-01-01

    The maximum use temperature of noble metal thin film thermocouples of 1100 C (2000 F) may not be adequate for use on components in the increasingly harsh conditions of advanced aircraft and next generation launch technology. Ceramic-based thermocouples are known for their high stability and robustness at temperatures exceeding 1500 C, but are typically found in the form of rods or probes. NASA Glenn Research Center is investigating the feasibility of ceramics as thin film thermocouples for extremely high temperature applications to take advantage of the stability and robustness of ceramics and the non-intrusiveness of thin films. This paper will discuss the current state of development in this effort.

  19. Modeling of Mechanical Properties of Advanced Nanostructured Ceramic Composites

    DTIC Science & Technology

    2010-03-15

    of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently...nucleation of nanograins near crack tips and its role as a special toughening mechanism in ceramic nanocomposites; (vii) generation of nanoscale tracks at...mechanical properties 16. SECURITY CLASSIFICATION OF : a . REPORT b. ABSTRACT c. THIS PAGE 17. LIMITATION OF ABSTRACT 18. NUMBER OF PAGES

  20. The Structural Ceramics Database: Technical Foundations

    PubMed Central

    Munro, R. G.; Hwang, F. Y.; Hubbard, C. R.

    1989-01-01

    The development of a computerized database on advanced structural ceramics can play a critical role in fostering the widespread use of ceramics in industry and in advanced technologies. A computerized database may be the most effective means of accelerating technology development by enabling new materials to be incorporated into designs far more rapidly than would have been possible with traditional information transfer processes. Faster, more efficient access to critical data is the basis for creating this technological advantage. Further, a computerized database provides the means for a more consistent treatment of data, greater quality control and product reliability, and improved continuity of research and development programs. A preliminary system has been completed as phase one of an ongoing program to establish the Structural Ceramics Database system. The system is designed to be used on personal computers. Developed in a modular design, the preliminary system is focused on the thermal properties of monolithic ceramics. The initial modules consist of materials specification, thermal expansion, thermal conductivity, thermal diffusivity, specific heat, thermal shock resistance, and a bibliography of data references. Query and output programs also have been developed for use with these modules. The latter program elements, along with the database modules, will be subjected to several stages of testing and refinement in the second phase of this effort. The goal of the refinement process will be the establishment of this system as a user-friendly prototype. Three primary considerations provide the guidelines to the system’s development: (1) The user’s needs; (2) The nature of materials properties; and (3) The requirements of the programming language. The present report discusses the manner and rationale by which each of these considerations leads to specific features in the design of the system. PMID:28053397

  1. Silicon-Based Ceramic-Matrix Composites for Advanced Turbine Engines: Some Degradation Issues

    NASA Technical Reports Server (NTRS)

    Thomas-Ogbuji, Linus U. J.

    2000-01-01

    SiC/BN/SiC composites are designed to take advantage of the high specific strengths and moduli of non-oxide ceramics, and their excellent resistance to creep, chemical attack, and oxidation, while circumventing the brittleness inherent in ceramics. Hence, these composites have the potential to take turbine engines of the future to higher operating temperatures than is achievable with metal alloys. However, these composites remain developmental and more work needs to be done to optimize processing techniques. This paper highlights the lingering issue of pest degradation in these materials and shows that it results from vestiges of processing steps and can thus be minimized or eliminated.

  2. Optical properties of CAD-CAM ceramic systems.

    PubMed

    Della Bona, Alvaro; Nogueira, Audrea D; Pecho, Oscar E

    2014-09-01

    To evaluate the direct transmittance (T%), translucency, opacity and opalescence of CAD-CAM ceramic systems and the correlation between the translucency parameter (TP) and the contrast ratio (CR). Specimens of shades A1, A2 and A3 (n=5) were fabricated from CAD-CAM ceramic blocks (IPS e.max(®) CAD HT and LT, IPS Empress(®) CAD HT and LT, Paradigm™ C, and VITABLOCS(®) Mark II) and polished to 1.0±0.01mm in thickness. A spectrophotometer (Lambda 20) was used to measure T% on the wavelength range of 400-780nm. Another spectrophotometer (VITA Easyshade(®) Advance) was used to measure the CIE L(*)a(*)b(*) coordinates and the reflectance value (Y) of samples on white and black backgrounds. TP, CR and the opalescence parameter (OP) were calculated. Data were statistically analysed using VAF (variance accounting for) coefficient with Cauchy-Schwarz inequality, one-way ANOVA, Tukey's test, Bonferroni correction and Pearson's correlation. T% of some ceramic systems is dependent on the wavelength. The spectral behaviour showed a slight and constant increase in T% up to approximately 550nm, then some ceramics changed the behaviour as the wavelength gets longer. TP and CR values ranged, respectively, from 16.79 to 21.69 and from 0.52 to 0.64 (r(2)=-0.97). OP values ranged from 3.01 to 7.64. The microstructure of CAD-CAM ceramic systems influenced the optical properties. TP and CR showed a strong correlation for all ceramic systems evaluated. Yet, all ceramics showed some degree of light transmittance. In addition to shade, this study showed that other optical properties influence on the natural appearance of dental ceramics. Copyright © 2014 Elsevier Ltd. All rights reserved.

  3. Design and characterization of Yb and Nd doped transparent ceramics for high power laser applications: recent advancements

    NASA Astrophysics Data System (ADS)

    Lapucci, A.; Vannini, M.; Ciofini, M.; Pirri, A.; Nikl, M.; Li, J.; Esposito, L.; Biasini, V.; Hostasa, J.; Goto, T.; Boulon, G.; Maksimov, R.; Gizzi, L.; Labate, L.; Toci, G.

    2017-01-01

    We report a review on our recent developments in Yttebium and Neodymium doped laser ceramics, along two main research lines. The first is the design and development of Yb:YAG ceramics with non uniform doping distribution, for the management of thermo-mechanical stresses and for the mitigation of ASE: layered structures have been produced by solid state reactive sintering, using different forming processes (spray drying and cold press of the homogenized powders, tape cast of the slurry); samples have been characterized and compared to FEM analysis. The second is the investigation of Lutetium based ceramics (such as mixed garnets LuYAG and Lu2O3); this interest is mainly motivated by the favorable thermal properties of these hosts under high doping. We recently obtained for the first time high efficiency laser emission from Yb doped LuYAG ceramics. The investigation on sesquioxides has been focused on Nddoped Lu2O3 ceramics, fabricated with the Spark Plasma Sintering method (SPS). We recently achieved the first laser emission above 1 W from Nd doped Lu2O3 ceramics fabricated by SPS.

  4. AGT (Advanced Gas Turbine) technology project

    NASA Technical Reports Server (NTRS)

    1988-01-01

    An overall summary documentation is provided for the Advanced Gas Turbine Technology Project conducted by the Allison Gas Turbine Division of General Motors. This advanced, high risk work was initiated in October 1979 under charter from the U.S. Congress to promote an engine for transportation that would provide an alternate to reciprocating spark ignition (SI) engines for the U.S. automotive industry and simultaneously establish the feasibility of advanced ceramic materials for hot section components to be used in an automotive gas turbine. As this program evolved, dictates of available funding, Government charter, and technical developments caused program emphases to focus on the development and demonstration of the ceramic turbine hot section and away from the development of engine and powertrain technologies and subsequent vehicular demonstrations. Program technical performance concluded in June 1987. The AGT 100 program successfully achieved project objectives with significant technology advances. Specific AGT 100 program achievements are: (1) Ceramic component feasibility for use in gas turbine engines has been demonstrated; (2) A new, 100 hp engine was designed, fabricated, and tested for 572 hour at operating temperatures to 2200 F, uncooled; (3) Statistical design methodology has been applied and correlated to experimental data acquired from over 5500 hour of rig and engine testing; (4) Ceramic component processing capability has progressed from a rudimentary level able to fabricate simple parts to a sophisticated level able to provide complex geometries such as rotors and scrolls; (5) Required improvements for monolithic and composite ceramic gas turbine components to meet automotive reliability, performance, and cost goals have been identified; (6) The combustor design demonstrated lower emissions than 1986 Federal Standards on methanol, JP-5, and diesel fuel. Thus, the potential for meeting emission standards and multifuel capability has been initiated

  5. Novel technique for preparing Ca- and P-containing ceramic coating on Ti-6Al-4V by micro-arc oxidation.

    PubMed

    Yu, Sirong; Yang, Xizhen; Yang, Long; Liu, Yaohui; Yu, Yingjie

    2007-11-01

    A novel technique for preparing the Ca- and P-containing ceramic coating on Ti-6Al-4V alloy by micro-arc oxidation (MAO) was developed successfully in this paper. In the new technique, Ti alloy first was micro-arc oxidated in P-containing electrolyte, and then it was micro-arc oxidated in Ca-containing electrolyte. This technique can avoid the undesired chemical reaction between Ca-containing salt and P-containing salt in electrolyte. The surface morphologies, composition, and phases of MAO coatings were studied by means of SEM, EDS, and XRD. The results show that the P- and Ca-containing coating on Ti-6Al-4V alloy contains Ti, TiO(2) (rutile), alpha-Ca(PO(3))(2), CaTiO(3), and AlTi(3). There are many small and uniform pores in the coating. Most of these pores are coterminous. The microhardness of the coating is 720 HV and higher than that of Ti-6Al-4V alloy (220 HV). The coating is more wear-resistant than Ti-6Al-4V alloy under the lubricant of the artificial saliva and not easy to desquamate from the substrate of Ti-6Al-4V alloy.

  6. High-throughput method to predict extrusion pressure of ceramic pastes.

    PubMed

    Cao, Kevin; Liu, Yang; Tucker, Christopher; Baumann, Michael; Grit, Grote; Lakso, Steven

    2014-04-14

    A new method was developed to measure the rheology of extrudable ceramic pastes using a Hamilton MicroLab Star liquid handler. The Hamilton instrument, normally used for high throughput liquid processing, was expanded to function as a low pressure capillary rheometer. Diluted ceramic pastes were forced through the modified pipettes, which produced pressure drop data that was converted to standard rheology data. A known ceramic paste containing cellulose ether was made and diluted to various concentrations in water. The most dilute paste samples were tested in the Hamilton instrument and the more typical, highly concentrated, ceramic paste were tested with a hydraulic ram extruder fitted with a capillary die and pressure measurement system. The rheology data from this study indicates that the dilute high throughput method using the Hamilton instrument correlates to, and can predict, the rheology of concentrated ceramic pastes normally used in ceramic extrusion production processes.

  7. Ceramics-bonded Nd-Fe-B-type magnet with high electrical resistivity

    NASA Astrophysics Data System (ADS)

    Kang, M. S.; Kwon, H. W.; Kim, D. H.; Lee, J. G.; Yu, J. H.

    2018-05-01

    Ceramics-bonded magnet with remarkably high electrical resistivity was fabricated by hot-pressing the mixture of Nd13.6Fe73.6Co6.6Ga0.6B5.6 alloy melt-spun flakes and dielectric Bi2O3-SiO2-B2O3 ceramics powder with low melting point. Coercivity of the ceramics-bonded magnet decreased with increasing the addition of ceramics binder, and this was attributed to the increased demagnetizing factor. Thin oxidized layer on the flake surface formed by reaction between the flake and oxide binder also contributed to reducing coercivity in the ceramics-bonded magnet. Highly resistive ceramics-bonded magnet containing 30 vol% ceramics binder still had good magnetic performance and high mechanical strength at 175 oC: iHc = 5 kOe, Mr = 4.8 kG, (BH)max = 4.3 MGOe, and over 900 MPa.

  8. Interpreting equilibrium-conductivity and conductivity-relaxation measurements to establish thermodynamic and transport properties for multiple charged defect conducting ceramics.

    PubMed

    Zhu, Huayang; Ricote, Sandrine; Coors, W Grover; Kee, Robert J

    2015-01-01

    A model-based interpretation of measured equilibrium conductivity and conductivity relaxation is developed to establish thermodynamic, transport, and kinetics parameters for multiple charged defect conducting (MCDC) ceramic materials. The present study focuses on 10% yttrium-doped barium zirconate (BZY10). In principle, using the Nernst-Einstein relationship, equilibrium conductivity measurements are sufficient to establish thermodynamic and transport properties. However, in practice it is difficult to establish unique sets of properties using equilibrium conductivity alone. Combining equilibrium and conductivity-relaxation measurements serves to significantly improve the quantitative fidelity of the derived material properties. The models are developed using a Nernst-Planck-Poisson (NPP) formulation, which enables the quantitative representation of conductivity relaxations caused by very large changes in oxygen partial pressure.

  9. Evaluation of the bond strength of resin cements used to lute ceramics on laser-etched dentin.

    PubMed

    Giray, Figen Eren; Duzdar, Lale; Oksuz, Mustafa; Tanboga, Ilknur

    2014-07-01

    The purpose of this study was to investigate the shear bond strength (SBS) of two different adhesive resin cements used to lute ceramics on laser-etched dentin. Erbium, chromium: yttrium, scandium, gallium, garnet (Er,Cr:YSGG) laser irradiation has been claimed to improve the adhesive properties of dentin, but results to date have been controversial, and its compatibility with existing adhesive resin cements has not been conclusively determined. Two adhesive cements, one "etch-and-rinse" [Variolink II (V)] and one "self-etch" [Clearfil Esthetic Cement (C)] luting cement, were used to lute ceramic blocks (Vita Celay Blanks, Vita) onto dentin surfaces. In total, 80 dentin specimens were distributed randomly into eight experimental groups according to the dentin surface-etching technique used Er,Cr:YSGG laser and Er:YAG laser: (1) 37% orthophosphoric acid+V (control group), (2) Er,Cr:YSGG laser+V, (3) Er,Cr:YSGG laser+acid+V, (4) Er:YAG laser+V, (5) Er:YAG laser+acid+V, (6) C, (7) Er,Cr:YSGG laser+C, and (8) Er:YAG laser+C. Following these applications, the ceramic discs were bonded to prepared surfaces and were shear loaded in a universal testing machine until fracture. SBS was recorded for each group in MPa. Shear test values were evaluated statistically using the Mann-Whitney U test. No statistically significant differences were evident between the control group and the other groups (p>0.05). The Er,Cr:YSGG laser+A+V group demonstrated significantly higher SBS than did the Er,Cr:YSGG laser+V group (p=0.034). The Er,Cr:YSGG laser+C and Er:YAG laser+C groups demonstrated significantly lower SBS than did the C group (p<0.05). Dentin surfaces prepared with lasers may provide comparable ceramic bond strengths, depending upon the adhesive cement used.

  10. Better ceramics through chemistry. 4

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

    Zelinski, B.J.J.; Brinker, C.J.; Clark, D.E.

    1990-01-01

    At this year's meeting, research into the area of reaction mechanisms and kinetics of silicon species remained strong, while significant advances in the area of structure and properties of modified and unmodified metal alkoxide species were reported. The complementary area of processing in water based systems also received considerable attention with emphasis being placed on the hydrolysis behavior of ions in solution. The nature of particle/aggregate growth was also a major topic of discussion with papers being presented on the role of aggregation in particle growth and on the nature and rheology of concentrated suspensions. Important developments in the areamore » of mechanical properties of aerogels, fibers and films were presented as well as research into techniques for in situ monitoring of films during dip coating. Continued advances in applications which utilize solution derived ceramics were also reported. These applications included GRIN lenses, planar waveguides, optical filters and switches, transpiration cooled windows, dye-polymer composites for nonlinear optics, dielectrics and electro-optic materials including PLZT's and the niobates, and chemical sensors. Finally, one of the meeting highlights was a special evening session on biomimetics: ceramic processing in natural systems.« less

  11. Process of producing a ceramic matrix composite article and article formed thereby

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

    Corman, Gregory Scot; McGuigan, Henry Charles; Brun, Milivoj Konstantin

    A CMC article and process for producing the article to have a layer on its surface that protects a reinforcement material within the article from damage. The method entails providing a body containing a ceramic reinforcement material in a matrix material that contains a precursor of a ceramic matrix material. A fraction of the reinforcement material is present and possibly exposed at a surface of the body. The body surface is then provided with a surface layer formed of a slurry containing a particulate material but lacking the reinforcement material of the body. The body and surface layer are heatedmore » to form the article by converting the precursor within the body to form the ceramic matrix material in which the reinforcement material is contained, and by converting the surface layer to form the protective layer that covers any fraction of the reinforcement material exposed at the body surface.« less

  12. Continuous fiber ceramic matrix composites for heat engine components

    NASA Technical Reports Server (NTRS)

    Tripp, David E.

    1988-01-01

    High strength at elevated temperatures, low density, resistance to wear, and abundance of nonstrategic raw materials make structural ceramics attractive for advanced heat engine applications. Unfortunately, ceramics have a low fracture toughness and fail catastrophically because of overload, impact, and contact stresses. Ceramic matrix composites provide the means to achieve improved fracture toughness while retaining desirable characteristics, such as high strength and low density. Materials scientists and engineers are trying to develop the ideal fibers and matrices to achieve the optimum ceramic matrix composite properties. A need exists for the development of failure models for the design of ceramic matrix composite heat engine components. Phenomenological failure models are currently the most frequently used in industry, but they are deterministic and do not adequately describe ceramic matrix composite behavior. Semi-empirical models were proposed, which relate the failure of notched composite laminates to the stress a characteristic distance away from the notch. Shear lag models describe composite failure modes at the micromechanics level. The enhanced matrix cracking stress occurs at the same applied stress level predicted by the two models of steady state cracking. Finally, statistical models take into consideration the distribution in composite failure strength. The intent is to develop these models into computer algorithms for the failure analysis of ceramic matrix composites under monotonically increasing loads. The algorithms will be included in a postprocessor to general purpose finite element programs.

  13. Impedance spectroscopic and dielectric properties of nanosized Y2/3Cu3Ti4O12 ceramic

    NASA Astrophysics Data System (ADS)

    Sharma, Sunita; Yadav, Shiv Sundar; Singh, M. M.; Mandal, K. D.

    2014-11-01

    Yttrium Copper Titanate (Y2/3Cu3Ti4O12) nanoceramic is structurally analogous to CaCu3Ti4O12 (CCTO). X-ray diffraction (XRD) of Y2/3Cu3Ti4O12 (YCTO) shows the presence of all normal peaks of CCTO. SEM micrograph exhibits the presence of bimodal grains of size ranging from 1-2 μm. Bright field TEM image clearly displays nanocrystalline particle which is supported by presence of a few clear rings in the corresponding selected area electron diffraction (SAED) pattern. It exhibits a high value of dielectric constant (ɛ‧ = 8434) at room temperature and 100 Hz frequency with characteristic relaxation peaks. Impedance and modulus studies revealed the presence of temperature-dependent Maxwell-Wagner type of relaxation in the ceramic.

  14. Performance Evaluations of Ceramic Wafer Seals

    NASA Technical Reports Server (NTRS)

    Dunlap, Patrick H., Jr.; DeMange, Jeffrey J.; Steinetz, Bruce M.

    2006-01-01

    Future hypersonic vehicles will require high temperature, dynamic seals in advanced ramjet/scramjet engines and on the vehicle airframe to seal the perimeters of movable panels, flaps, and doors. Seal temperatures in these locations can exceed 2000 F, especially when the seals are in contact with hot ceramic matrix composite sealing surfaces. NASA Glenn Research Center is developing advanced ceramic wafer seals to meet the needs of these applications. High temperature scrub tests performed between silicon nitride wafers and carbon-silicon carbide rub surfaces revealed high friction forces and evidence of material transfer from the rub surfaces to the wafer seals. Stickage between adjacent wafers was also observed after testing. Several design changes to the wafer seals were evaluated as possible solutions to these concerns. Wafers with recessed sides were evaluated as a potential means of reducing friction between adjacent wafers. Alternative wafer materials are also being considered as a means of reducing friction between the seals and their sealing surfaces and because the baseline silicon nitride wafer material (AS800) is no longer commercially available.

  15. [Study on high strength mica-based machinable glass-ceramic].

    PubMed

    Li, Hong; Ran, Junguo; Gou, Li; Wang, Fanghu

    2004-02-01

    The phase constitution, microstructure and properties of a new type of machinable glass-ceramics containing fluorophlogopite-type (FPT) Ca-mica for used in restorative dentistry were investigated. According to the results of X-ray diffraction (XRD) and energy-dispersive spectrometry(EDS), its main crystalline phases were FPT Ca-mica and t-ZrO2, together with few KxCa(1-x)/2Mg2Si4O10F2, m-ZrO2. The flexible strength was 235 MPa, which was nearly two times larger than that of the present mica-based dental materials, and the highest fracture toughness was 2.17 MPa.m1/2. The microstructure had a great effect on properties, the glass-ceramics contained a large volume, and the fine crystals showed higher strength. The material possessed typical microstructure of machinable glass-ceramics and displayed excellent machinability during drilling test and CAD/CAM.

  16. Electrolytic production of high purity aluminum using ceramic inert anodes

    DOEpatents

    Ray, Siba P.; Liu, Xinghua; Weirauch, Douglas A.; DiMilia, Robert A.; Dynys, Joseph M.; Phelps, Frankie E.; LaCamera, Alfred F.

    2002-01-01

    A method of producing commercial purity aluminum in an electrolytic reduction cell comprising ceramic inert anodes is disclosed. The method produces aluminum having acceptable levels of Fe, Cu and Ni impurities. The ceramic inert anodes used in the process may comprise oxides containing Fe and Ni, as well as other oxides, metals and/or dopants.

  17. Lithotripsy of gallstones by means of a quality-switched giant-pulse neodymium:yttrium-aluminum-garnet laser. Basic in vitro studies using a highly flexible fiber system.

    PubMed

    Hochberger, J; Gruber, E; Wirtz, P; Dürr, U; Kolb, A; Zanger, U; Hahn, E G; Ell, C

    1991-11-01

    The quality-switched neodymium:yttrium-aluminum-garnet laser represents a new instrument for athermal fragmentation of gallstones by transformation of optical energy into mechanical energy in the form of shock waves via local plasma formation. A highly flexible 300-micron fiber transmission system was used in basic investigations to determine the influence of varying pulse repetition rates (5-30 Hz) and pulse energies (15 and 20 mJ) on shock wave intensity and stone fragmentation in vitro for 105 biliary calculi of known size and chemical composition. After performance of 1200 shock wave pressure measurements using polyvinylidenefluoride hydrophones, stone fragmentation was analyzed by determination of fragment removal rates (volume of fragments removed per fragmentation time), ablation rates (mean volume removed per laser pulse), and median fragment sizes for each laser setting. With the quality-switched neodymium:yttrium-aluminum-garnet laser system, all concrements could be reliably disintegrated into small fragments (median diameter, 0.7-1.7 mm). Compared with pure cholesterol stones, a significantly higher fragment removal rate was achieved in cholesterol stones containing 30% calcium phosphate (P = 0.039), in cholesterol stones containing 20% pigment (P = 0.015), and in pure pigment stones (P = 0.007). Fragment removal rates, local shock wave pressures, and median grain sizes were significantly higher at a pulse energy of 20 mJ than with 15 mJ. Shock wave pressures showed a distinct dependence on pulse repetition rates at 20 mJ, yet not at 15 mJ. Because there is no evident hazard of thermal damage to tissue using the quality-switched neodymium:yttrium-aluminum-garnet laser, it appears to be a promising device for nonsurgical biliary stone therapy.

  18. Recent advances in understanding the reinforcing ability and mechanism of carbon nanotubes in ceramic matrix composites.

    PubMed

    Estili, Mehdi; Sakka, Yoshio

    2014-12-01

    Since the discovery of carbon nanotubes (CNTs), commonly referred to as ultimate reinforcement, the main purpose for fabricating CNT-ceramic matrix composites has been mainly to improve the fracture toughness and strength of the ceramic matrix materials. However, there have been many studies reporting marginal improvements or even the degradation of mechanical properties. On the other hand, those studies claiming noticeable toughening measured using indentation, which is an indirect/unreliable characterization method, have not demonstrated the responsible mechanisms applicable to the nanoscale, flexible CNTs; instead, those studies proposed those classical methods applicable to microscale fiber/whisker reinforced ceramics without showing any convincing evidence of load transfer to the CNTs. Therefore, the ability of CNTs to directly improve the macroscopic mechanical properties of structural ceramics has been strongly questioned and debated in the last ten years. In order to properly discuss the reinforcing ability (and possible mechanisms) of CNTs in a ceramic host material, there are three fundamental questions to our knowledge at both the nanoscale and macroscale levels that need to be addressed: (1) does the intrinsic load-bearing ability of CNTs change when embedded in a ceramic host matrix?; (2) when there is an intimate atomic-level interface without any chemical reaction with the matrix, could one expect any load transfer to the CNTs along with effective load bearing by them during crack propagation?; and (3) considering their nanometer-scale dimensions, flexibility and radial softness, are the CNTs able to improve the mechanical properties of the host ceramic matrix at the macroscale when individually, intimately and uniformly dispersed? If so, how? Also, what is the effect of CNT concentration in such a defect-free composite system? Here, we briefly review the recent studies addressing the above fundamental questions. In particular, we discuss the new

  19. Recent advances in understanding the reinforcing ability and mechanism of carbon nanotubes in ceramic matrix composites

    PubMed Central

    Estili, Mehdi; Sakka, Yoshio

    2014-01-01

    Since the discovery of carbon nanotubes (CNTs), commonly referred to as ultimate reinforcement, the main purpose for fabricating CNT–ceramic matrix composites has been mainly to improve the fracture toughness and strength of the ceramic matrix materials. However, there have been many studies reporting marginal improvements or even the degradation of mechanical properties. On the other hand, those studies claiming noticeable toughening measured using indentation, which is an indirect/unreliable characterization method, have not demonstrated the responsible mechanisms applicable to the nanoscale, flexible CNTs; instead, those studies proposed those classical methods applicable to microscale fiber/whisker reinforced ceramics without showing any convincing evidence of load transfer to the CNTs. Therefore, the ability of CNTs to directly improve the macroscopic mechanical properties of structural ceramics has been strongly questioned and debated in the last ten years. In order to properly discuss the reinforcing ability (and possible mechanisms) of CNTs in a ceramic host material, there are three fundamental questions to our knowledge at both the nanoscale and macroscale levels that need to be addressed: (1) does the intrinsic load-bearing ability of CNTs change when embedded in a ceramic host matrix?; (2) when there is an intimate atomic-level interface without any chemical reaction with the matrix, could one expect any load transfer to the CNTs along with effective load bearing by them during crack propagation?; and (3) considering their nanometer-scale dimensions, flexibility and radial softness, are the CNTs able to improve the mechanical properties of the host ceramic matrix at the macroscale when individually, intimately and uniformly dispersed? If so, how? Also, what is the effect of CNT concentration in such a defect-free composite system? Here, we briefly review the recent studies addressing the above fundamental questions. In particular, we discuss the new

  20. Progress in NMR Studies of Liquid Ceramic Materials

    NASA Astrophysics Data System (ADS)

    Marzke, Robert F.; Piwowarczyk, Jeremy; Boucher, Susan; Wolf, George H.

    2003-10-01

    The availability of molten, levitated samples of Al-containing ceramics at temperatures of 2,000^oC and higher permits a broad range of important materials to be investigated by the powerful techniques of NMR.footnote Coutures, J-P., Massiot, D., Bessada, C., Echegut, P., Rifflet, J-C. & Taulelle F., Etude par RMN 27Al daluminates liquides dans le domaine 1600-2100 ^oC. C.R. Acad. Sci. Paris, 1990, 310, 1041. Standard measurements of chemical shift as a function of composition yield information concerning the bonding of Al and the structure of liquid phases, for both novel and well-studied refractory materials. Studies of incoherent motions in a sample, such as Al diffusion or time-dependent convective currents, may also be performed when magnetic field gradients are incorporated into the experimental NMR probe. Recent advances are reviewed, in several research areas.

  1. Advanced Turbine Technology Applications Project (ATTAP)

    NASA Technical Reports Server (NTRS)

    1989-01-01

    ATTAP activities during the past year were highlighted by an extensive materials assessment, execution of a reference powertrain design, test-bed engine design and development, ceramic component design, materials and component characterization, ceramic component process development and fabrication, component rig design and fabrication, test-bed engine fabrication, and hot gasifier rig and engine testing. Materials assessment activities entailed engine environment evaluation of domestically supplied radial gasifier turbine rotors that were available at the conclusion of the Advanced Gas Turbine (AGT) Technology Development Project as well as an extensive survey of both domestic and foreign ceramic suppliers and Government laboratories performing ceramic materials research applicable to advanced heat engines. A reference powertrain design was executed to reflect the selection of the AGT-5 as the ceramic component test-bed engine for the ATTAP. Test-bed engine development activity focused on upgrading the AGT-5 from a 1038 C (1900 F) metal engine to a durable 1371 C (2500 F) structural ceramic component test-bed engine. Ceramic component design activities included the combustor, gasifier turbine static structure, and gasifier turbine rotor. The materials and component characterization efforts have included the testing and evaluation of several candidate ceramic materials and components being developed for use in the ATTAP. Ceramic component process development and fabrication activities were initiated for the gasifier turbine rotor, gasifier turbine vanes, gasifier turbine scroll, extruded regenerator disks, and thermal insulation. Component rig development activities included combustor, hot gasifier, and regenerator rigs. Test-bed engine fabrication activities consisted of the fabrication of an all-new AGT-5 durability test-bed engine and support of all engine test activities through instrumentation/build/repair. Hot gasifier rig and test-bed engine testing

  2. Estimation of Slow Crack Growth Parameters for Constant Stress-Rate Test Data of Advanced Ceramics and Glass by the Individual Data and Arithmetic Mean Methods

    NASA Technical Reports Server (NTRS)

    Choi, Sung R.; Salem, Jonathan A.; Holland, Frederic A.

    1997-01-01

    The two estimation methods, individual data and arithmetic mean methods, were used to determine the slow crack growth (SCG) parameters (n and D) of advanced ceramics and glass from a large number of room- and elevated-temperature constant stress-rate ('dynamic fatigue') test data. For ceramic materials with Weibull modulus greater than 10, the difference in the SCG parameters between the two estimation methods was negligible; whereas, for glass specimens exhibiting Weibull modulus of about 3, the difference was amplified, resulting in a maximum difference of 16 and 13 %, respectively, in n and D. Of the two SCG parameters, the parameter n was more sensitive to the estimation method than the other. The coefficient of variation in n was found to be somewhat greater in the individual data method than in the arithmetic mean method.

  3. Determination of elastic modulus of ceramics using ultrasonic testing

    NASA Astrophysics Data System (ADS)

    Sasmita, Firmansyah; Wibisono, Gatot; Judawisastra, Hermawan; Priambodo, Toni Agung

    2018-04-01

    Elastic modulus is important material property on structural ceramics application. However, bending test as a common method for determining this property require particular specimen preparation. Furthermore, elastic modulus of ceramics could vary because it depends on porosity content. For structural ceramics industry, such as ceramic tiles, this property is very important. This drives the development of new method to improve effectivity or verification method as well. In this research, ultrasonic testing was conducted to determine elastic modulus of soda lime glass and ceramic tiles. The experiment parameter was frequency of probe (1, 2, 4 MHz). Characterization of density and porosity were also done for analysis. Results from ultrasonic testing were compared with elastic modulus resulted from bending test. Elastic modulus of soda-lime glass based on ultrasonic testing showed excellent result with error 2.69% for 2 MHz probe relative to bending test result. Testing on red and white ceramic tiles were still contained error up to 41% and 158%, respectively. The results for red ceramic tile showed trend that 1 MHz probe gave better accuracy in determining elastic modulus. However, testing on white ceramic tile showed different trend. It was due to the presence of porosity and near field effect.

  4. SPIO-labeled Yttrium Microspheres for MR Imaging Quantification of Transcatheter Intrahepatic Delivery in a Rodent Model

    PubMed Central

    Li, Weiguo; Zhang, Zhuoli; Gordon, Andrew C.; Chen, Jeane; Nicolai, Jodi; Lewandowski, Robert J.; Omary, Reed A.

    2016-01-01

    Purpose To investigate the qualitative and quantitative impacts of labeling yttrium microspheres with increasing amounts of superparamagnetic iron oxide (SPIO) material for magnetic resonance (MR) imaging in phantom and rodent models. Materials and Methods Animal model studies were approved by the institutional Animal Care and Use Committee. The r2* relaxivity for each of four microsphere SPIO compositions was determined from 32 phantoms constructed with agarose gel and in eight concentrations from each of the four compositions. Intrahepatic transcatheter infusion procedures were performed in rats by using each of the four compositions before MR imaging to visualize distributions within the liver. For quantitative studies, doses of 5, 10, 15, or 20 mg 2% SPIO-labeled yttrium microspheres were infused into 24 rats (six rats per group). MR imaging R2* measurements were used to quantify the dose delivered to each liver. Pearson correlation, analysis of variance, and intraclass correlation analyses were performed to compare MR imaging measurements in phantoms and animal models. Results Increased r2* relaxivity was observed with incremental increases of SPIO microsphere content. R2* measurements of the 2% SPIO–labeled yttrium microsphere concentration were well correlated with known phantom concentrations (R2 = 1.00, P < .001) over a broader linear range than observed for the other three compositions. Microspheres were heterogeneously distributed within each liver; increasing microsphere SPIO content produced marked signal voids. R2*-based measurements of 2% SPIO–labeled yttrium microsphere delivery were well correlated with infused dose (intraclass correlation coefficient, 0.98; P < .001). Conclusion MR imaging R2* measurements of yttrium microspheres labeled with 2% SPIO can quantitatively depict in vivo intrahepatic biodistribution in a rat model. © RSNA, 2015 Online supplemental material is available for this article. PMID:26313619

  5. Method for removing volatile components from a ceramic article, and related processes

    DOEpatents

    Klug, Frederic Joseph; DeCarr, Sylvia Marie

    2002-01-01

    A method of removing substantially all of the volatile component in a green, volatile-containing ceramic article is disclosed. The method comprises freezing the ceramic article; and then subjecting the frozen article to a vacuum for a sufficient time to freeze-dry the article. Frequently, the article is heated while being freeze-dried. Use of this method efficiently reduces the propensity for any warpage of the article. The article is often formed from a ceramic slurry in a gel-casting process. A method for fabricating a ceramic core used in investment casting is also described.

  6. Effect of yttrium on martensite-austenite phase transformation temperatures and high temperature oxidation kinetics of Ti-Ni-Hf high-temperature shape memory alloys

    NASA Astrophysics Data System (ADS)

    Kim, Jeoung Han; Kim, Kyong Min; Yeom, Jong Taek; Young, Sung

    2016-03-01

    The effect of yttrium (< 5.5 at%) on the martensite-austenite phase transformation temperatures, microstructural evolution, and hot workability of Ti-Ni-Hf high-temperature shape memory alloys is investigated. For these purposes, differential scanning calorimetry, hot compression, and thermo-gravimetric tests are conducted. The phase transformation temperatures are not noticeably influenced by the addition of yttrium up to 4.5 at%. Furthermore, the hot workability is not significantly affected by the yttrium addition up to 1.0 at%. However, when the amount of yttrium addition exceeds 1.0 at%, the hot workability deteriorates significantly. In contrast, remarkable improvement in the high temperature oxidation resistance due to the yttrium addition is demonstrated. The total thickness of the oxide layers is substantially thinner in the Y-added specimen. In particular, the thickness of (Ti,Hf) oxide layer is reduced from 200 µm to 120 µm by the addition of 0.3 at% Y.

  7. Interdisciplinary research on the nature and properties of ceramic materials

    NASA Technical Reports Server (NTRS)

    1980-01-01

    The advancement of material performance and design methodology as related to brittle materials was investigated. The processing and properties of ceramic materials as related to design requirements was also studied.

  8. Constitutive Theory Developed for Monolithic Ceramic Materials

    NASA Technical Reports Server (NTRS)

    Janosik, Lesley A.

    1998-01-01

    With the increasing use of advanced ceramic materials in high-temperature structural applications such as advanced heat engine components, the need arises to accurately predict thermomechanical behavior that is inherently time-dependent and that is hereditary in the sense that the current behavior depends not only on current conditions but also on the material's thermomechanical history. Most current analytical life prediction methods for both subcritical crack growth and creep models use elastic stress fields to predict the time-dependent reliability response of components subjected to elevated service temperatures. Inelastic response at high temperatures has been well documented in the materials science literature for these material systems, but this issue has been ignored by the engineering design community. From a design engineer's perspective, it is imperative to emphasize that accurate predictions of time-dependent reliability demand accurate stress field information. Ceramic materials exhibit different time-dependent behavior in tension and compression. Thus, inelastic deformation models for ceramics must be constructed in a fashion that admits both sensitivity to hydrostatic stress and differing behavior in tension and compression. A number of constitutive theories for materials that exhibit sensitivity to the hydrostatic component of stress have been proposed that characterize deformation using time-independent classical plasticity as a foundation. However, none of these theories allow different behavior in tension and compression. In addition, these theories are somewhat lacking in that they are unable to capture the creep, relaxation, and rate-sensitive phenomena exhibited by ceramic materials at high temperatures. The objective of this effort at the NASA Lewis Research Center has been to formulate a macroscopic continuum theory that captures these time-dependent phenomena. Specifically, the effort has focused on inelastic deformation behavior associated

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

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

    Crawford, Charles L.

    2015-09-24

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

  10. Surfaces and interfaces of glass and ceramics; Proceedings of the International Symposium on Special Topics in Ceramics, Alfred University, Alfred, N.Y., August 27-29, 1973

    NASA Technical Reports Server (NTRS)

    Frechette, V. D. (Editor); Lacourse, W. C.; Burdick, V. L.

    1974-01-01

    The characterization of surfaces and interfaces is considered along with the infrared spectra of several N-containing compounds absorbed on montmorillonites, applications of surface characterization techniques to glasses, the observation of electronic spectra in glass and ceramic surfaces, a method for determining the preferred orientation of crystallites normal to a surface, and the friction and wear behavior of glasses and ceramics. Attention is given to the wear behavior of cast surface composites, an experimental investigation of the dynamic and thermal characteristics of the ceramic stock removal process, a dynamic elastic model of ceramic stock removal, and the structure and properties of solid surfaces. Individual items are announced in this issue.

  11. Creep of Refractory Fibers and Modeling of Metal and Ceramic Matrix Composite Creep Behavior

    NASA Technical Reports Server (NTRS)

    Tewari, S.N.

    1995-01-01

    Our concentration during this research was on the following subprograms. (1) Ultra high vacuum creep tests on 218, ST300 and WHfC tungsten and MoHfC molybdenum alloy wires, temperature range from 1100 K to 1500 K, creep time of 1 to 500 hours. (2) High temperature vacuum tensile tests on 218, ST300 and WHfC tungsten and MoHfC molybdenum alloy wires. (3) Air and vacuum tensile creep tests on polycrystalline and single crystal alumina fibers, such as alumina-mullite Nextel fiber, yttrium aluminum ganet (YAG) and Saphikon, temperature range from 1150 K to 1470 K, creep time of 2 to 200 hours. (4) Microstructural evaluation of crept fibers, TEM study on the crept metal wires, SEM study on the fracture surface of ceramic fibers. (5) Metal Matrix Composite creep models, based on the fiber creep properties and fiber-matrix interface zone formation.

  12. Degradation, bioactivity, and cytocompatibility of diopside, akermanite, and bredigite ceramics.

    PubMed

    Wu, Chengtie; Chang, Jiang

    2007-10-01

    The aim of this study was to investigate the effect of three bioceramics in the CaO-SiO(2)-MgO systems with different composition on the in vitro degradation, bioactivity, and cytocompatibility. The degradation was evaluated through the activation energy of Si ion release from ceramics and the weight loss of the ceramics in Tris-HCl buffers. The in vitro bioactivity of the ceramics was investigated by analysis of apatite-formation ability in the simulated body fluid (SBF). The cytocompatibility was evaluated through osteoblast morphology and proliferation. The results showed that the activation energy of Si ion release increased and the degradation decreased from bredigite to diopside ceramics with the increase of Mg content, and the apatite-formation ability in SBF decreased. The Ca, Si, and Mg containing ionic products from three ceramics could stimulate cell proliferation at lower concentration, and inhibit cell proliferation with the increase of ion concentrations. Furthermore, osteoblasts could adhere, spread, and proliferate on three ceramic disks, and cell proliferation on diopside was more obvious than that on other two ceramic disks.

  13. Alternating-Composition Layered Ceramic Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Miller, Robert A.; Zhu, Dongming

    2008-01-01

    Ceramic thermal and environmental barrier coatings (T/EBCs) that contain multiple layers of alternating chemical composition have been developed as improved means of protecting underlying components of gas-turbine and other heat engines against both corrosive combustion gases and high temperatures.

  14. Mott insulator-to-metal transition in yttrium-doped CaIrO₃.

    PubMed

    Gunasekera, J; Chen, Y; Kremenak, J W; Miceli, P F; Singh, D K

    2015-02-11

    We report on the study of insulator-to-metal transition in post-perovskite compound CaIrO3. It is discovered that a gradual chemical substitution of calcium by yttrium leads to the onset of strong metallic behavior in this compound. This observation is in stark contrast to BaIrO3, which preserves its Mott insulating behavior despite excess of the charge carriers due to yttrium doping. Magnetic measurements reveal that both compounds tend to exhibit magnetic character irrespective of the chemical substitution of Ca or Ba. We analyze these unusual observations in light of recent researches that suggest that CaIrO3 does not necessarily possess j = 1/2 ground state due to structural distortion. The insulator-to-metal transition in CaIrO3 will spur new researches to explore more exotic ground state, including superconductivity, in post-perovskite Mott insulators.

  15. The Preparation of Silicon-Containing Ceramics by Organosilicon Polymer Pyrolysis

    DTIC Science & Technology

    1988-06-25

    polymer , of composition [(CH3SiHNH)a(CH3SiNb]m, gives a black solid, a mixture of SiC , Si3N4, and some free carbon, on pyrolysis ...nitride (eq. 1) [7] is a possibility. 5 Si3N 4(s) + C (s) , 3 SiC (s) +2 N2(g) (1) The study of the pyrolysis products of preceramic polymers is not...approximately one, pyrolysis of the product polymer gave a black ceramic solid in 84% yield which analysis showed to have a formal composition (1 SiC +

  16. Heat Conduction in Ceramic Coatings: Relationship Between Microstructure and Effective Thermal Conductivity

    NASA Technical Reports Server (NTRS)

    Kachanov, Mark

    1998-01-01

    Analysis of the effective thermal conductivity of ceramic coatings and its relation to the microstructure continued. Results (obtained in Task 1) for the three-dimensional problem of heat conduction in a solid containing an inclusion (or, in particular, cavity - thermal insulator) of the ellipsoidal shape, were further advanced in the following two directions: (1) closed form expressions of H tensor have been derived for special cases of ellipsoidal cavity geometry: spheroid, crack-like spheroidal cavity and needle shaped spheroidal cavity; (2) these results for one cavity have been incorporated to construct heat energy potential for a solid with many spheroidal cavities (in the approximation of non-interacting defects). This problem constitutes a basic building block for further analyses.

  17. Advanced ultrasonic measurement methodology for non-invasive interrogation and identification of fluids in sealed containers

    NASA Astrophysics Data System (ADS)

    Tucker, Brian J.; Diaz, Aaron A.; Eckenrode, Brian A.

    2006-03-01

    Government agencies and homeland security related organizations have identified the need to develop and establish a wide range of unprecedented capabilities for providing scientific and technical forensic services to investigations involving hazardous chemical, biological, and radiological materials, including extremely dangerous chemical and biological warfare agents. Pacific Northwest National Laboratory (PNNL) has developed a prototype portable, hand-held, hazardous materials acoustic inspection prototype that provides noninvasive container interrogation and material identification capabilities using nondestructive ultrasonic velocity and attenuation measurements. Due to the wide variety of fluids as well as container sizes and materials encountered in various law enforcement inspection activities, the need for high measurement sensitivity and advanced ultrasonic measurement techniques were identified. The prototype was developed using a versatile electronics platform, advanced ultrasonic wave propagation methods, and advanced signal processing techniques. This paper primarily focuses on the ultrasonic measurement methods and signal processing techniques incorporated into the prototype. High bandwidth ultrasonic transducers combined with an advanced pulse compression technique allowed researchers to 1) obtain high signal-to-noise ratios and 2) obtain accurate and consistent time-of-flight (TOF) measurements through a variety of highly attenuative containers and fluid media. Results of work conducted in the laboratory have demonstrated that the prototype experimental measurement technique also provided information regarding container properties, which will be utilized in future container-independent measurements of hidden liquids.

  18. Failure of a novel ceramic-on-ceramic hip resurfacing prosthesis.

    PubMed

    Matharu, Gulraj S; Daniel, Joseph; Ziaee, Hena; McMinn, Derek J W

    2015-03-01

    We report the early failure of five ceramic-on-ceramic hip resurfacings (CoCHRs). The ceramic used for the acetabular liner was a novel ceramic-composite (two thirds polyurethane and one third alumina ceramic). All cases were revised for increasing metal ion levels (blood cobalt 3.93-208.0 μg/l and chromium 1.57-17.5 μg/l) due to ceramic liner fracture and/or accelerated wear of the ceramic femoral head coating. Patients underwent bearing exchange and revision using primary hip arthroplasty implants at a mean of 3.0 years following CoCHR. Intraoperatively all patients had metallosis. At 1 to 2 years of follow-up blood metal ions normalized with no complications. We do not recommend this particular type of ceramic-on-ceramic bearing for hip resurfacing. Copyright © 2014 Elsevier Inc. All rights reserved.

  19. Novel Translucent and Strong Submicron Alumina Ceramics for Dental Restorations.

    PubMed

    Zhao, M; Sun, Y; Zhang, J; Zhang, Y

    2018-03-01

    An ideal ceramic restorative material should possess excellent aesthetic and mechanical properties. We hypothesize that the high translucency and strength of polycrystalline ceramics can be achieved through microstructural tailoring. The aim of this study is to demonstrate the superior optical and mechanical properties of a new class of submicron grain-sized alumina ceramics relative to the current state-of-the-art dental ceramic materials. The translucency, the in-line transmission ( T IT ) in particular, of these submicron alumina ceramics has been examined with the Rayleigh-Gans-Debye light-scattering model. The theoretical predictions related very well with the measured T IT values. The translucency parameter ( TP) and contrast ratio ( CR) of the newly developed aluminas were measured with a reflectance spectrophotometer on a black-and-white background. For comparison, the T IT , TP, and CR values for a variety of dental ceramics, mostly measured in-house but also cited from the literature, were included. The flexural strength of the aluminas was determined with the 4-point bending test. Our findings have shown that for polycrystalline alumina ceramics, an average grain size <1 µm coupled with a porosity level <0.7% could yield translucency values ( T IT , TP, CR) similar to those of the commercial high-translucency porcelains. These values are far superior to the high-translucency lithium disilicate glass-ceramic and zirconias, including the most translucent cubic-containing zirconias. The strength of these submicron grain-sized aluminas was significantly higher than that of the cubic-containing zirconia (e.g., Zpex Smile) and lithia-based glass-ceramics (e.g., IPS e.max CAD HT). A coarse-grained alumina could also reach a translucency level comparable to that of dental porcelain. However, the relatively low strength of this material has limited its clinical indications to structurally less demanding applications, such as orthodontic brackets. With a combined

  20. Advanced Sensor and Packaging Technologies for Intelligent Adaptive Engine Controls (Preprint)

    DTIC Science & Technology

    2013-05-01

    combination of micro-electromechanical systems (MEMS) sensor technology, novel ceramic materials, high - temperature electronics, and advanced harsh...with simultaneous pressure measurements up to 1,000 psi. The combination of a high - temperature , high -pressure-ratio compressor system, and adaptive...combination of micro-electromechanical systems (MEMS) sensor technology, novel ceramic materials, high temperature electronics, and advanced harsh