Mechanical properties up to 1900 K of Al2O3/Er3Al5O12/ZrO2 eutectic ceramics grown by the laser floating zone method

Directionally solidified Al2O3–Er3Al5O12–ZrO2 eutectic rods were processed using the laser floating zone method at growth rates of 25, 350and 750 mm/h to obtain microstructures with different domain size. The mechanical properties were investigated as a function of the processing rate. The hardness, 15.6 GPa, and the fracture toughness, 4 MPa m1/2, obtained from Vickers indentation at room temperature were practically independent of the size of the eutectic phases. However, the flexural strength increased as the domain size decreased, reaching outstanding strength values close to 3 GPa in the samples grown at 750 mm/h. A high retention of the flexural strength was observed up to 1500 K in the materials processed at 25 and 350 mm/h, while superplastic behaviour was observed at 1700 K in the eutectic rods solidified at the highest rate of 750 mm/h

Relationship between residual stresses and mechanical behavior in ceramic composites

En este trabajo, materiales de tipo alúmina/Y-TZP (ZrO2 tetragonal, estabilizada con 3 mol. % Y2O3), como sistema cerámico popular por sus mejoradas propiedades mecánicas en comparación con las cerámicas de alúmina puras, han sido estudiados en términos de propiedades mecánicas y tensiones residuales. El novedoso método de colado en cinta, consistente en el apilamiento de cintas de cerámica verde a temperatura ambiente y el uso de bajas presiones, se ha escogido para la presente investigación con el fin de poder aprovechar al máximo el futuro desarrollo de materiales laminados de alúmina-óxido de circonio. Se han determinado las propiedades de los materiales obtenidos por este nuevo método de procesamiento comparándolas con las de los materiales obtenidos por “slip casting”, con el fin de analizar si el método propuesto afecta a la microestructura y, por tanto, a las propiedades mecánicas y tensiones residuales propias de estos materiales. Para analizar la idoneidad del proceso de fabricación, utilizado para evitar la presencia de discontinuidades en las intercaras entre las láminas así como otros fenómenos que puedan interferir con las propiedades mecánicas, se estudiaron materiales cerámicos con la misma composición en cintas. Por otra parte también se analizó el efecto de la adición de óxido de circonio sobre la aparición de tensiónes residuales en cerámicas Al2O3/Y-TZP, teniendo en cuenta su notable influencia sobre las propiedades microestructurales y mecánicas de los materiales, así como el requisito de co-sinterización de capas con diferentes materiales compuestos en materiales laminados. La caracterización del material incluye la determinación de la densidad, el análisis de la microestructura, la obtención de las propiedades mecánicas (módulo de elasticidad, dureza, resistencia a la flexión y tenacidad de fractura) así como de las tensiones residuales. En combinación con otros métodos de medida tradicionales, la nanoindentación también se empleó como una técnica adicional para la medida del módulo de elasticidad y de la dureza. Por otro lado, diferentes técnicas de difracción con neutrones, tanto las basadas en longitud de onda constante (CW) como en tiempo de vuelo (TOF), han sido empleadas para la medición fiable de la deformación residual a través del grosor en muestras a granel. Las tensiones residuales fueron determinadas con elevada precisión, aplicando además métodos de análisis apropiados, como por ejemplo el refinamiento de Rietveld. Las diferentes fases en cerámicas sinterizadas, especialmente las de zirconia, se examinaron con detalle mediante el análisis de Rietveld, teniendo en cuenta el complicado polimorfismo del Óxido de Zirconio (ZrO2) así como las posibles transformaciones de fase durante el proceso de fabricación. Los efectos del contenido de Y-TZP en combinación con el nuevo método de procesamiento sobre la microestructura, el rendimiento mecánico y las tensiones residuales de los materiales estudiados (Al2O3/Y-TZP) se resumen en el presente trabajo. Finalmente, los mecanismos de endurecimiento, especialmente los relacionados con las tensiones residuales, son igualmente discutidos. In present work, Alumina/Y-TZP (tetragonal ZrO2 stabilized with 3 mol% Y2O3) materials, as an popular ceramic system with improved mechanical properties compared with the pure alumina ceramics, have been studied in terms of mechanical properties and residual stresses. The novel tape casting method, which involved the stacking of green ceramics tapes at room temperature and using low pressures, is selected for manufacturing and investigation, in order to take full advantage of the future development of alumina-zirconia laminated materials. Features of materials obtained by the new processing method are determined and compared with those of materials obtained by conventional slip casting in a plaster mold, in order to study whether the proposed method of processing affects microstructure and thereby the mechanical properties and residual stresses characteristics of materials. To analyse the adequacy of the manufacturing process used to avoid the presence of discontinuities at the interfaces between the sheets and other phenomena that interfere with the mechanical properties, ceramic materials with the same composition in tapes were investigated. Moreover, the effect of addition of zirconia on residual stress development of Al2O3/Y-TZP ceramics were taken into investigations, considering its significantly influence on the microstructure and mechanical properties of materials as well as the requirement of co-sintering of layers with different composites in laminated materials. The characterization includes density, microstructure, mechanical properties (elastic modulus, hardness, flexure strength and fracture toughness) and residual stresses. Except of the traditional measurement methods, nanoindentation technique was also used as an additional measurement of the elastic modulus and hardness. Neutron diffraction, both the constant-wavelength (CW) and time-of-flight (TOF) neutron diffraction techniques, has been used for reliable through-thickness residual strain measurement in bulk samples. Residual stresses were precisely determined combined with appropriate analysis methods, e.g. the Rietveld refinement. The phase compositions in sintered ceramics especially the ones of zirconia were accurately examined by Rietveld analysis, considering the complex polymorph of ZrO2 and the possible phase transformation during manufacturing process. Effects of Y-TZP content and the new processing method on the microstructure, mechanical performance and residual stresses were finally summarized in present studied Al2O3/Y-TZP materials. The toughening mechanisms, especially the residual stresses related toughening, were theoretically discussed.

The Composition and Drivers of Energy Prices and Costs in Energy-Intensive Industries: The Case of Ceramics, Glass and Chemicals. CEPS Special Report No. 85, 27 March 2014

In May 2013, the European Commission received a mandate from the European Council to “to present an analysis of the composition and drivers of energy prices and costs in Member States, with a particular focus on the impact on households, SMEs and energy intensive industries, and looking more widely at the EU's competitiveness vis-à-vis its global economic counterparts”. Following such mandate and in view of the preparation by the Commission of a Communication and a Staff Working Document, DG Enterprise and Industry commissioned CEPS to carry out a set of studies aimed at providing well-grounded evidence about the evolution and composition of energy prices and costs at plant level within individual industry sectors. A team of CEPS researchers conducted the research, led by Christian Egenhofer and Lorna Schrefler. Vasileios Rizos served as Project Coordinator. Other CEPS researchers contributing to the project included: Fabio Genoese, Andrea Renda, Andrei Marcu, Julian Wieczorkiewicz, Susanna Roth, Federico Infelise, Giacomo Luchetta, Lorenzo Colantoni, Wijnand Stoefs, Jacopo Timini and Felice Simonelli. In addition to an introductory report entitled “About the Study and Cross-Sectoral Analysis”, CEPS prepared five sectoral case studies: two on ceramics (wall and floor tiles and bricks and roof tiles), two on chemicals (ammonia and chlorine) and one on flat glass. Each of these six studies has been consolidated in this single volume for free downloading on the CEPS website. The specific objective was to complement information already available at macro level with a bottom-up perspective on the operating conditions that industry stakeholders need to deal with, in terms of energy prices and costs. The approach chosen was based on case studies for a selected set (sub-)sectors amongst energy-intensive industries. A standard questionnaire was circulated and respondents were sampled according to specified criteria. Data and information collected were finally presented in a structured format in order to guarantee comparability of results between the different (sub-)sectors analysed. The complete set of files can also be downloaded from the European Commission’s website: http://ec.europa.eu/enterprise/newsroom/cf/itemdetail.cfm?item_id=7238&lang=en&title=Study-on-composition-and-drivers-of-energy-prices-and-costs-in-energy-intnsive-industries The results of the studies were presented at a CEPS Conference held on February 26th along with additional evidence from other similar studies. The presentations can be downloaded at: http://www.ceps.eu/event/level-and-drivers-eu-energy-prices-energy-inten...

Summaries of physical research in research in metallurgy, solid state physics and ceramics.

"January 1957 (TISE Issuance Date)."

Summaries of physical research in research in metallurgy, solid state physics and ceramics.

"July 1959 (TIS Issuance Date)."

Summaries of the UDAEC basic research programs in metallurgy, solid state physics and ceramics.

"January 1964 (DTIE Issuance Date)."

Summaries of the UDAEC basic research programs in metallurgy, solid state physics and ceramics : (fiscal year 1964)

"January 1965 (DTIE Issuance Date)."

Asiatic Art, VII century B.C.-XVIII century A.D., including sculpture in bronze & stone, ceramics, miniatures and textiles.

Exhibition and sale at the American Art Galleries, New York.

Summaries of the UDAEC basic research programs in metallurgy, solid state physics and ceramics.

"June 1961 (OIT Issuance Date)."

Transformation toughened ceramics for the Heavy Duty Diesel Engine Technology Program.

Energy Department, Office of Vehicle and Engine Research and Development, Washington, D.C.

Opportunities for advanced ceramics to meet the needs of the industries of the future /

"DOE/ORO 2076."