Showing papers on "Ceramic published in 2001"
Book•
03 Oct 2001
TL;DR: In this article, the fundamental core theory of functional properties and properties of materials are discussed. But the authors focus on the physical properties of thin films and artificial multilayers, rather than the structural properties of the materials themselves.
Abstract: Subject areas: Functional Phenomena. Electrical and thermal transport in normal solids. Physics and application of superconductors. Lattice properties and thermodynamics. Metal-gas reactions and electrochemistry. Magnetism and electronic properties and bulk solids. Hard and soft magnetic materials, manufacturing and applications. Magneto-optical and optical recording. Magnetic recording magnetic fluids. Physical properties of thin films and artificial multilayers. Optical and dielectric phenomena. Fundamental Core Theory. Fundamentals of materials science. Amorphous materials. Nuclear materials and irradiation effects. Biomedical and dental materials. Natural products and biomimetics. Carbon. Wood and paper. Characterization of materials. Surfaces: structure and properties. Miscellaneous. Structural Materials. Metal extraction, melting and refining. Metal processing. Structure, transformations and properties, light metals. Structure, transformations and properties, ferrous metals. Ceramic processing. Structure, transformations, properties in ceramics. Composites: MMC, CMC, PMC. Applications: aerospace automotive, sports, other. Applications: building. Modeling: atomic, microscale, large scale. Materials selection, life cycle costs, environmental tradeoffs, etc. Corrosion. Structural Phenomena. Elasticity-residual stress. Brittle fracture. Plastic deformation in static loading. Microscopic models of plasticity. Deformation and damage under cyclic load. Creep, strength and fatigue at elevated temperature. Mechanical properties of surfaces and in micro-dimensions. Deformation-related processing. Mechanical testing and nondestructive inspection. Polymers and Materials Chemistry. Crystalline polymers. Glassy amorphous and liquid crystalline polymers. Conducting and semiconducting polymers and organics. Elastomers, networks and gels. Block copolymers. Industrial polymerization chemistry. New synthesis methods for speciality polymers. Polymer processing. Inorganic materials chemistry. Organic/inorganic hybrid materials. Self-assembling materials chemistry. Liquid crystals. Functional Materials. Physics and chemistry of semiconductors. Semiconducting devices. Defects in semiconductors. Evaluation of semiconductors. Crystal growth. Epitaxial growth. Semiconductor processing and IC fabrication. Nonlinear optical materials. Electroceramics. Packaging.
1,400 citations
TL;DR: In this paper, the authors give a brief outline of the field that has emerged on the basis of theoretical models on porous as well as non-porous membranes, and discuss mainly the solution cast polymeric membranes.
667 citations
Patent•
22 Jun 2001TL;DR: In this paper, the authors present an environmental barrier for an OLED, which consists of a foundation and a cover, each of which has a top of three layers of a first polymer layer, a second ceramic layer, and a third polymer layer.
Abstract: The present invention is an environmental barrier for an OLED. The environmental barrier has a foundation and a cover. Both the foundation and the cover have a top of three layers of (a) a first polymer layer, (b) a ceramic layer, and (c) a second polymer layer. The foundation and/or the cover may have a at least one set of intermediate barrier each having (a) an intermediate polymer layer with (b) an intermediate ceramic layer thereon. In a preferred embodiment, the foundation has a substrate upon which at least a top is deposited. An OLED is constructed upon the top, opposite the substrate. The cover of at least a top then placed over the OLED. The placement may be by gluing or preferably by vacuum deposition. For use as a display, it is preferred that either the ceramic layer(s) in the foundation, cover or both is substantially transparent to the light emitted by the OLED. Each layer of the foundation and the cover is preferably vacuum deposited. Vacuum deposition includes monolayer spreading under vacuum, plasma deposition, flash evaporation and combinations thereof. It is further preferred that all layers are deposited and cured between rolls or rollers to avoid the defects that may be caused by abrasion over a roll or roller.
649 citations
TL;DR: In this article, a model to account for the role of the ceramic fillers in enhancing the transport properties of PEO-based composite polymer electrolytes is proposed, supported by a series of specifically addressed electrochemical tests which included the determination of the conductivity and of the lithium transference number of various composite electrolyte samples differing from the type of the surface states of a ceramic filler.
630 citations
TL;DR: In this paper, the performance of SOFC single cells is not only determined by intrinsic material properties, but also due to the fabrication technology respectively the microstructure at the electrode/electrolyte-interfaces.
Abstract: Solid oxide fuel cells are a forward looking technology for a highly efficient, environmental friendly power generation. A SOFC is a multilayer structure consisting of ceramic and metallic materials with different electrical transport properties. All components have to show a well adjusted thermal expansion behavior, chemical compatibility of material interfaces and chemical stability in the prevailing atmospheres. The performance of SOFC single cells is not only determined by intrinsic material properties. There is a significant influence due to the fabrication technology respectively the microstructure at the electrode/electrolyte-interfaces. The performance of cells can only be improved by the application of elevated materials using appropriate technologies.
488 citations
TL;DR: In this paper, the pore formation mechanism was discussed in relation to the starting slurry concentration and sintering temperature, and pore structure was substantially affected by these effects.
Abstract: Porous ceramics with complex pore structure were synthesized by a freeze-dry process. Freezing-in of a water-based ceramics slurry was done while controlling the growth direction of the ice. Sublimation marks of the ice were generated by drying under reduced pressure. Porous ceramics having a complex pore structure were obtained by sintering the green body: aligned macroscopic open pores contained micropores in their internal walls. The pore structure was substantially affected by the starting slurry concentration and sintering temperature. The pore formation mechanism is discussed in relation to these effects.
395 citations
TL;DR: In this paper, materials for thermal conduction are reviewed, including materials exhibiting high thermal conductivity (such as metals, carbons, ceramics and composites), and thermal interface materials such as polymer-based and silicate-based pastes and solder.
394 citations
Patent•
05 Apr 2001
TL;DR: A reusable ceramic skin-piercing device as mentioned in this paper is capable of piercing the skin so as to make a sample of biological fluid available for an assay, but it is not suitable for use in medical applications.
Abstract: A reusable ceramic skin-piercing device. The skin-piercing device is capable of piercing the skin so as to make a sample of biological fluid available for an assay. In one embodiment, the skin-piercing device includes a skin-piercing element which is heated prior to use to a sufficiently high temperature to kill or deactivate pathogenic microorganisms. The device is heat-sterilized, being heated by passing an electrical current through a resistive element in thermal contact with the heat-conducting ceramic piercer. In another embodiment, the skin-piercing device includes a sleeve of elastomeric material with a sterilizing agent disposed in contact with the skin-piercing element. The sterilizing agent sterilizes the skin-piercing element after use. The skin-piercing element is made of a hard refractory ceramic material. The ceramic material is optionally a composite, for example, a composite of a ceramic material and a metal, or multiple ceramic materials.
367 citations
31 Jan 2001-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, Mg was reinforced with SiC nanoparticles by powder metallurgical technique and the mechanical properties of the new material were investigated by tensile tests and creep measurements and the microstructure of the composites were examined by light and transmission electron microscopy (TEM).
Abstract: Mg was reinforced with SiC nanoparticles by powder metallurgical technique. The SiC nanoparticles were generated by laser-induced gas phase reaction in a flow reactor and had a median particle diameter of 30 nm. In order to distribute the nanoparticles in the Mg matrix, Mg micropowder with a median particle diameter of 40 μm was mixed or ball milled with the nanoscaled ceramic powder followed by hot extrusion. The mechanical properties of the new material were investigated by tensile tests and creep measurements and the microstructure of the composites were examined by light and transmission electron microscopy (TEM).
353 citations
TL;DR: In this paper, a review of the current work carried out on mixedoxide systems such as SnO 2 -WO 3, TiO 2-WO3 and SnO2 -TiO 2 with the ultimate aim of the application in gas sensing devices is presented.
334 citations
TL;DR: A review of available information on factors which contribute to poor wetting between ceramic phases, and liquid metals is presented in this article, focusing on aluminium, a common MMC matrix material.
TL;DR: In this paper, the authors present a review of aqueous deposition routes for oxide materials for electronic applications, focusing on oxide materials with an emphasis on oxide material for semiconductor applications.
Abstract: Many techniques for the synthesis of ceramic thin films from aqueous solutions at low temperatures (25–100°C) have been reported. This paper reviews non-electrochemical, non-hydrothermal, low-temperature aqueous deposition routes, with an emphasis on oxide materials for electronic applications. Originally used for sulfide and selenide thin films, such techniques have also been applied to oxides since the 1970's. Films of single oxides (e.g., transition metal oxides, In2O3, SiO2, SnO2) and multicomponent films (doped ZnO, Cd2SnO4, ZrTiO4, ZrO2-Y2O3, Li-Co-O spinel, ferrites, perovskites) have been produced. The maximum thicknesses of the films obtained have ranged from 100 to 1000 nm, and deposition rates have ranged from 2 to 20,000 nm/h. Compared to vapor-deposition techniques, liquid-deposition routes offer lower capital equipment costs, lower processing temperatures, and flexibility in the choice of substrates with respect to topography and thermal stability. Compared to sol-gel techniques, the routes reviewed here offer lower processing temperatures, lower shrinkage, and (being based on aqueous precursors) lower costs and the potential for reduced environmental impact. This review emphasizes the influence of solution chemistry and process design on the microstructures and growth rates of the films. The current understanding of the mechanisms of film formation is presented, and the advantages and limitations of these techniques are discussed.
TL;DR: In this paper, the performance of planar-type solid oxide fuel cells (SOFC) interconnectors was investigated in the presence of Fe-16Cr alloys and showed that the oxide scale grows in accordance with the parabolic rate law.
TL;DR: In this article, the microstructural evolution of anatase-based commercial TiO2 powders, with an average size of 100 nm, at high temperatures was investigated using transmission electron microscopy analysis, and new information regarding the nature and mechanisms of this polymorphic reaction was revealed.
Abstract: Titania (TiO2) is an important electronic ceramic material for use in diverse applications such as gas sensors, catalysts, dielectrics, and ceramic membranes. TiO2 exists as several polymorphic phases, most commonly as rutile or anatase. This paper investigates the microstructural evolution of anatase-based commercial TiO2 powders, with an average size of 100 nm, at high temperatures. These powders transform to the rutile structure at 1000°C. The characteristics of the anatase-to-rutile transformation have been studied using transmission electron microscopy analysis, and new information regarding the nature and mechanisms of this polymorphic reaction has been revealed.
TL;DR: In this article, a series of BaTiO3/monomer suspensions were photocured into thin wafers, and the dielectric permittivity of the composites was investigated at frequencies from 100 Hz to 10 GHz and at temperatures from −140 to +150 °C.
Abstract: Dielectric properties of model BaTiO3/polymer composites were measured over a broad frequency and temperature range. A series of BaTiO3/monomer suspensions were photocured into thin wafers. The wafers were equipped with aluminum electrodes, and the dielectric permittivity of the composites was investigated at frequencies from 100 Hz to 10 GHz and at temperatures from −140 to +150 °C. It has been found that for the same BaTiO3 loading dielectric characteristics of the composites strongly depend of the type of polymer. Polar polymers increase dielectric constant of the composites at low frequencies but have little effect at gigahertz frequencies. Dielectric losses of the composites show a maximum at some intermediate frequency within megahertz to gigahertz range that reflects the relaxation behavior of the polymer matrix. The magnitude of the losses increases with increasing polarity of the polymer component. At constant frequency and temperature, the composites follow a linear relationship between logarith...
TL;DR: A number of studies have been carried out on the preparation and characterization of hybrid polyimide composites, and the purpose of this review is to give a brief account of the strategies used for this purpose and to describe some of the properties of the resulting composites as discussed by the authors.
Abstract: A number of polyimides have gained considerable importance as high-performance polymers during the last 2 decades primarily because of their excellent thermal stability and toughness. Some applications, however, require property enhancements and the desired improvements can often be obtained through incorporation of ceramic-like particles such as silica. Such hybrid inorganic−organic composites are frequently obtained using the in situ generation of the dispersed inorganic phase by the sol−gel technique. A number of studies have now been carried out on the preparation and characterization of such hybrid polyimide composites, and the purpose of this review is to give a brief account of the strategies used for this purpose and to describe some of the properties of the resulting composites.
TL;DR: It is demonstrated that radial cracking from the lower core layer surface is the dominant failure mode for ceramic layer thicknesses much below 1 mm, and an approach may be used to establish a scientific, materials-based foundation for designing next-generation crown layer structures.
Abstract: Ceramic-based crowns, particularly molar crowns, can fail prematurely from accumulation of fracture and other damage in continual occlusal contact. Damage modes depend on ceramic types (especially microstructures), flaw states, loading conditions, and geometric factors. These damage modes can be simulated and characterized in the laboratory with the use of Hertzian contact testing on monolayer, bilayer, and trilayer structures to represent important aspects of crown response in oral function. This article reviews the current dental materials knowledge base of clinically relevant contact-induced damage in ceramic-based layer structures in the context of all-ceramic crown lifetimes. It is proposed that simple contact testing protocols that make use of sphere indenters on model flat, ceramic-based layer structures—ceramic/polymer bilayers (simulating monolithic ceramic crowns on dentin) and ceramic/ceramic/polymer trilayers (simulating veneer/core all-ceramic crowns on dentin)—can provide useful relations for predicting critical occlusal loads to induce lifetime-threatening fracture. It is demonstrated that radial cracking from the lower core layer surface is the dominant failure mode for ceramic layer thicknesses much below 1 mm. Such an approach may be used to establish a scientific, materials-based foundation for designing next-generation crown layer structures. (J Prosthet Dent 2001;86:495-510.)
TL;DR: ZrO2-NiCr functionally graded material (FGM) was developed by powder metallurgical process as discussed by the authors, and the suitable fabrication procedure of FGM was determined.
TL;DR: In this paper, the hydrophilic parts of the polymer are completely integrated into the ceramic phase, thereby leading to a quasi-two-phase system, allowing for a more rational hybrid morphology design based on current understanding of the phase behavior of block copolymers and copolymer−homopolymer mixtures.
Abstract: The study of amphiphilic polymer based functional organic−inorganic hybrid materials is an emerging research area offering enormous scientific and technological promise. Here, we show that employing poly(isoprene-block-ethylene oxide) block copolymers (PI-b-PEO) and a silicon precursor, which contains a polymerizable organic moiety, unprecedented morphology control on the nanoscale is obtained. This control is based on a unique polymer−ceramic interface, which is characterized using a multi-nuclei solid-state NMR approach. The results show that the hydrophilic parts of the polymer are completely integrated into the ceramic phase, thereby leading to a quasi “two-phase system”, allowing for a more rational hybrid morphology design based on the current understanding of the phase behavior of block copolymers and copolymer−homopolymer mixtures. Examination of the full phase space of the hybrid materials reveals the existence of a new bicontinuous cubic structure that was not known to exist in polymer systems. ...
TL;DR: The tensile flow behaviour and deformed microstructure of the material indicate that superplasticity is due to a combination of limited grain growth in the constitutive phases and the intervention of dislocation-induced plasticity in the zirconium oxide phase.
Abstract: High-strain-rate superplasticity describes the ability of a material to sustain large plastic deformation in tension at high strain rates of the order of 10-2 to 10-1 s-1 and is of great technological interest for the shape-forming of engineering materials. High-strain-rate superplasticity has been observed in aluminium-based and magnesium-based alloys. But for ceramic materials, superplastic deformation has been restricted to low strain rates of the order of 10-5 to 10-4 s-1 for most oxides and nitrides with the presence of intergranular cavities leading to premature failure. Here we show that a composite ceramic material consisting of tetragonal zirconium oxide, magnesium aluminate spinel and alpha-alumina phases exhibits superplasticity at strain rates up to 1 s-1. The composite also exhibits a large tensile elongation, exceeding 1,050 per cent for a strain rate of 0.4 s-1. The tensile flow behaviour and deformed microstructure of the material indicate that superplasticity is due to a combination of limited grain growth in the constitutive phases and the intervention of dislocation-induced plasticity in the zirconium oxide phase. We suggest that the present results hold promise for the application of shape-forming technologies to ceramic materials.
Book•
25 Jun 2001
TL;DR: In this article, the authors present a survey of the physical properties of solids and their properties as well as their properties in terms of properties such as optical properties of materials, magnetic properties, and structural properties.
Abstract: Preface. List of Tables. Introduction. STRUCTURE OF MATERIALS. Structure of Crystals. Bonding in Solids. Diffraction and the Reciprocal Lattice. Order and Disorder in Solids. PHYSICAL PROPERTIES OF MATERIALS. Phonons. Thermally Activated Processes, Phase Diagrams, and Phase Transitions. Electrons in Solids: Electrical and Thermal Properties. Optical Properties of Materials. Magnetic Properties of Materials. Mechanical Properties of Materials. CLASSES OF MATERIALS. Semiconductors. Metals and Alloys. Ceramics. Polymers. Dielectric and Ferroelectric Materials. Superconductors. Magnetic Materials. Optical Materials. SURFACES, THIN FILMS, INTERFACES, AND MULTILAYERS. Surfaces. Thin Films, Interfaces, and Multilayers. SYNTHESIS AND PROCESSING OF MATERIALS. Synthesis and Processing of Materials. Characterization of Materials. Appendix WA: Thermodynamics. Appendix WB: Statistical Mechanics. Appendix WC: Quantum Mechanics. Materials Index. Index.
TL;DR: In this article, two palettes, characteristic of the production of the Sevres Factory (Manufacture Nationale de Sevres), and representative of ancient glazing techniques, were studied, focusing on the different Raman peaks arising from coloured coatings specific to ancient artefacts.
Abstract: Two palettes, characteristic of the production of the Sevres Factory (Manufacture Nationale de Sevres), and representative of ancient glazing techniques, were studied. One was made with coloured glazes/enamels on Bisque (1050 °C) and the other one was composed of Moufle (880 °C) painting colours. Spectra specific to the white (opacifiers), yellow (including Naples yellow), green, pink, ‘brown–red’ and black coatings/paintings were considered. Emphasis was placed on the different Raman peaks arising from coloured coatings specific to ancient artefacts: greens obtained with dissolved Cu ions or from chromium pigments (Victoria green garnets), Naples yellows (Pb2Sb2O7 pyrochlore), green and black spinels and pink sphene. Attention was paid to the effect of pigment grain size on the Raman spectrum. To illustrate the capability of the method, we analysed some old artefacts from the eighteenth and nineteenth centuries. Copyright © 2001 John Wiley & Sons, Ltd.
TL;DR: In this paper, a unique porous ceramic with complex pore structure was synthesized by the freeze-dry process, where a water-based ceramic slurry was frozen while controlling the growth direction of ice, and sublimation of the ice were generated by drying it at a reduced pressure.
Abstract: A unique porous ceramic with complex pore structure was synthesized by the freeze-dry process. A water-based ceramic slurry was frozen while controlling the growth direction of ice, and sublimation of the ice were generated by drying it at a reduced pressure. By sintering this green body, a porous ceramic with complex pore structure was obtained, where macroscopically aligned open pores exceeding 10 μm in size contained minute pores of about 0.1 μm in their internal walls. Wide control of the porosity was possible by changing the concentration of the starting slurry. The pore size distribution as well as the microstructure were substantially affected by the freezing and sintering temperatures. Optimization of the synthesis conditions was investigated in order to obtain the desired pore structure.
Journal Article•
TL;DR: The novel direct ceramic machining (DCM) process allows an easy, reliable and rapid fabrication for all-ceramic dental restorations with high mechanical strength and good biocompatibility, and zirconia bridges fabricated by the DCM process are superior to In-Ceram Alumina and IPS Empress2.
Abstract: All-ceramic dental bridges for the molar region are not yet available at reasonable costs. The novel direct ceramic machining (DCM) process allows an easy, reliable and rapid fabrication for all-ceramic dental restorations with high mechanical strength and good biocompatibility. In DCM, an enlarged framework is easily milled out of a pre-fabricated porous ceramic blank made of zirconia. After sintering to full density, no further time-consuming hard machining with diamond tools is needed. For individual esthetical requirements, the framework is coated with a veneer porcelain. Compared to the commercially available In-Ceram Alumina and IPS Empress2 restorations, the mechanical strength of zirconia frameworks is twice as high, allowing the restorations to bear the high mastication forces in the molar region. In terms of reliability, zirconia bridges fabricated by the DCM process are also superior to In-Ceram Alumina and IPS Empress2. A clinical study of three-unit dental bridges in the molar region found no problems after the first year of observation.
TL;DR: The results show that calcium phosphate ceramics are osteoinductive in muscles of dogs, and the induced bone in both HA and BCP ceramic did neither disappear nor grow uncontrollably during the period as long as 2.5 years.
TL;DR: The theory of heat conduction in ceramics by phonons, and at high temperatures also by infrared radiation, is reviewed in this paper, where the phonon mean free path is limited by three-phonon interactions and by scattering of various imperfections.
Abstract: The theory of heat conduction in ceramics by phonons, and at high temperatures also by infrared radiation, is reviewed. The phonon mean free path is limited by three-phonon interactions and by scattering of various imperfections. Point defects scatter high-frequency phonons; extended imperfections, such as inclusions, pores, and grain boundaries, affect mainly low-frequency phonons. Thermal radiation is also scattered by imperfections, but of a larger size, such as splat boundaries and large pores. Porosity also reduces the effective index of refraction. For films there are also external boundaries, cracks, and splat boundaries, depending on the method of deposition. Examples discussed are cubic zirconia, titanium oxide, and uranium oxide. Graphite and graphene sheets, with two-dimensional phonon gas, are discussed briefly.
TL;DR: In this article, an edge crack in a strip of a functionally graded material (FGM) was studied under transient thermal loading conditions, where the FGM is assumed having constant Young's modulus and Poisson's ratio, but the thermal properties of the material vary along the thickness direction of the strip.
Abstract: An edge crack in a strip of a functionally graded material (FGM) is studied under transient thermal loading conditions. The FGM is assumed having constant Young's modulus and Poisson's ratio, but the thermal properties of the material vary along the thickness direction of the strip. Thus the material is elastically homogeneous but thermally nonhomogeneous. This kind of FGMs include some ceramic/ceramic FGMs such as TiC/SiC, MoSi2/Al2O3 and MoSi2/SiC, and also some ceramic/metal FGMs such as zirconia/nickel and zirconia/steel. A multi-layered material model is used to solve the temperature field. By using the Laplace transform and an asymptotic analysis, an analytical first order temperature solution for short times is obtained. Thermal stress intensity factors (TSIFs) are calculated for a TiC/SiC FGM with various volume fraction profiles of the constituent materials. It is found that the TSIF could be reduced if the thermally shocked cracked edge of the FGM strip is pure TiC, whereas the TSIF is increased if the thermally shocked edge is pure SiC.
TL;DR: In this paper, the impedance of a BaTiO3-based multilayer ceramic capacitor with a nickel internal electrode (Ni-MLCC) was investigated by measuring the frequency domain at various temperatures.
Abstract: The impedance of a BaTiO3 (BT)-based multilayer ceramic capacitor with a nickel internal electrode (Ni-MLCC) was investigated by measuring the frequency domain at various temperatures. All the obtained impedance data could be successfully fitted to a 4-RC section electrical equivalent network. The 4-RC section electrical equivalent network was successfully correlated to the microstructure: the core, the shell, the grain boundary, and the ceramic/internal electrode interface regions. Based on this electrical equivalent network, the electrical properties including the Curie-Weiss law, the current-voltage characteristics, and dc electrical degradation, were well explained. A model for the degradation behavior for BT-based Ni-MLCC with thin active layer thickness was proposed.
TL;DR: In this article, the possibilities and benefits of using ferroelectrics in polar phase in electrically controllable microwave devices are considered explicitly for the first time, and the authors consider the use of ceramic (bulk and thick film) ferro-electrics for industrial applications.
Abstract: Typical paraelectric materials (e.g., SrTiO/sub 3/, KTaO/sub 3/, Ba/sub x/Sr/sub 1-x/TiO/sub 3/, x 10 GHz) is of the order of 0.01 (at zero dc-bias field) at room temperature. Nevertheless, quite promising component and subsystem level devices are successfully demonstrated. Use of ceramic (bulk and thick film) ferroelectrics in tunable microwave devices, currently considered for industrial applications, offer cost reduction. In this paper, explicitly for the first time, we consider possibilities and benefits of using ferroelectrics in polar phase in electrically controllable microwave devices. Examples of using ferroelectrics in polar state (e.g., Na/sub 0.5/K/sub 0.5/NbO/sub 3/, SrTiO/sub 3/ in antiferroelectric phase) in electrically tunable devices are reported.