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YSZ
Yttria-stabilized zirconia (YSZ) is a ceramic in which the cubic crystal structure of zirconium dioxide is made stable at room temperature by an addition of yttrium oxide. These oxides are commonly called "zirconia" ( Zr O2) and "yttria" ( Y2 O3), hence the name. Stabilization Pure zirconium dioxide undergoes a phase transformation from monoclinic (stable at room temperature) to tetragonal (at about 1173 °C) and then to cubic (at about 2370 °C), according to the scheme : monoclinic (1173 °C) ↔ tetragonal (2370 °C) ↔ cubic (2690 °C) ↔ melt. Obtaining stable sintered zirconia ceramic products is difficult because of the large volume change, about 5%, accompanying the transition from tetragonal to monoclinic. Stabilization of the cubic polymorph of zirconia over wider range of temperatures is accomplished by substitution of some of the Zr4+ ions (ionic radius of 0.82 Å, too small for ideal lattice of fluorite characteristic for the c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Yttria-stabilized Zirconia (YSZ) Diagram
Yttria-stabilized zirconia (YSZ) is a ceramic in which the cubic crystal structure of zirconium dioxide is made stable at room temperature by an addition of yttrium oxide. These oxides are commonly called "zirconia" ( Zr O2) and "yttria" ( Y2 O3), hence the name. Stabilization Pure zirconium dioxide undergoes a phase transformation from monoclinic (stable at room temperature) to tetragonal (at about 1173 °C) and then to cubic (at about 2370 °C), according to the scheme : monoclinic (1173 °C) ↔ tetragonal (2370 °C) ↔ cubic (2690 °C) ↔ melt. Obtaining stable sintered zirconia ceramic products is difficult because of the large volume change, about 5%, accompanying the transition from tetragonal to monoclinic. Stabilization of the cubic polymorph of zirconia over wider range of temperatures is accomplished by substitution of some of the Zr4+ ions (ionic radius of 0.82 Å, too small for ideal lattice of fluorite characteristic for the cubi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solid Oxide Fuel Cell
A solid oxide fuel cell (or SOFC) is an electrochemical conversion device that produces electricity directly from oxidizing a fuel. Fuel cells are characterized by their electrolyte material; the SOFC has a solid oxide or ceramic electrolyte. Advantages of this class of fuel cells include high combined heat and power efficiency, long-term stability, fuel flexibility, low emissions, and relatively low cost. The largest disadvantage is the high operating temperature which results in longer start-up times and mechanical and chemical compatibility issues. Introduction Solid oxide fuel cells are a class of fuel cells characterized by the use of a solid oxide material as the electrolyte. SOFCs use a solid oxide electrolyte to conduct negative oxygen ions from the cathode to the anode. The electrochemical oxidation of the hydrogen, carbon monoxide or other organic intermediates by oxygen ions thus occurs on the anode side. More recently, proton-conducting SOFCs (PC-SOFC) are being de ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermal Barrier Coating
Thermal barrier coatings (TBCs) are advanced materials systems usually applied to metallic surfaces operating at elevated temperatures, such as gas turbine or aero-engine parts, as a form of exhaust heat management. These 100 μm to 2 mm thick coatings of thermally insulating materials serve to insulate components from large and prolonged heat loads and can sustain an appreciable temperature difference between the load-bearing alloys and the coating surface. In doing so, these coatings can allow for higher operating temperatures while limiting the thermal exposure of structural components, extending part life by reducing oxidation and thermal fatigue. In conjunction with active film cooling, TBCs permit working fluid temperatures higher than the melting point of the metal airfoil in some turbine applications. Due to increasing demand for more efficient engines running at higher temperatures with better durability/lifetime and thinner coatings to reduce parasitic mass fo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phosphor Thermometry
Phosphor thermometry is an optical method for surface temperature measurement. The method exploits luminescence emitted by phosphor material. Phosphors are fine white or pastel-colored inorganic powders which may be stimulated by any of a variety of means to luminesce, i.e. emit light. Certain characteristics of the emitted light change with temperature, including brightness, color, and afterglow duration. The latter is most commonly used for temperature measurement. History The first mention of temperature measurement utilizing a phosphor is in two patents originally filed in 1932 by Paul Neubert. Time dependence of luminescence Typically a short duration ultraviolet lamp or laser source illuminates the phosphor coating which in turn luminesces visibly. When the illuminating source ceases, the luminescence will persist for a characteristic time, steadily decreasing. The time required for the brightness to decrease to 1/e of its original value is known as the decay time or life ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ceramic
A ceramic is any of the various hard, brittle, heat-resistant and corrosion-resistant materials made by shaping and then firing an inorganic, nonmetallic material, such as clay, at a high temperature. Common examples are earthenware, porcelain, and brick. The earliest ceramics made by humans were pottery objects (''pots,'' ''vessels or vases'') or figurines made from clay, either by itself or mixed with other materials like silica, hardened and sintered in fire. Later, ceramics were glazed and fired to create smooth, colored surfaces, decreasing porosity through the use of glassy, amorphous ceramic coatings on top of the crystalline ceramic substrates. Ceramics now include domestic, industrial and building products, as well as a wide range of materials developed for use in advanced ceramic engineering, such as in semiconductors. The word "'' ceramic''" comes from the Greek word (), "of pottery" or "for pottery", from (), "potter's clay, tile, pottery". The earliest k ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electroceramics
Electroceramics is a class of ceramic materials used primarily for their electrical properties. While ceramics have traditionally been admired and used for their mechanical, thermal and chemical stability, their unique electrical, optical and magnetic properties have become of increasing importance in many key technologies including communications, energy conversion and storage, electronics and automation. Such materials are now classified under ''electroceramics'', as distinguished from other functional ceramics such as advanced structural ceramics. Historically, developments in the various subclasses of electroceramics have paralleled the growth of new technologies. Examples include: ferroelectrics - high dielectric capacitors, non-volatile memories; ferrites - data and information storage; solid electrolytes - energy storage and conversion; piezoelectrics - sonar; semiconducting oxides - environmental monitoring. Recent advances in these areas are described in thJournal of Ele ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crown (dentistry)
In dentistry, a crown most commonly refers to a dental cap, a type of dental restoration that completely caps or encircles a tooth or dental implant. A crown may be needed when a large cavity threatens the health of a tooth. A crown is typically bonded to the tooth by dental cement. They can be made from various materials, which are usually fabricated using ''indirect methods''. Crowns are used to improve the strength or appearance of teeth and to halt deterioration. While beneficial to dental health, the procedure and materials can be costly. The most common method of crowning a tooth involves taking a dental impression of a tooth prepared by a dentist, then fabricating the crown outside of the mouth. The crown can then be inserted at a subsequent dental appointment. This ''indirect method'' of tooth restoration allows use of strong restorative material requiring time-consuming fabrication under intense heat, such as casting metal or firing porcelain, that would not be po ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nernst Lamp
The Nernst lamp was an early form of incandescent lamp. Construction Nernst lamps did not use a glowing tungsten filament. Instead, they used a ceramic rod that was heated to incandescence. Because the rod (unlike tungsten wire) would not further oxidize when exposed to air, there was no need to enclose it within a vacuum or noble gas environment; the burners in Nernst lamps could operate exposed to the air and were only enclosed in glass to isolate the hot incandescent emitter from its environment. A ceramic of zirconium oxide – yttrium oxide was used as the glowing rod. Efficiency Developed by the German physicist and chemist Walther Nernst in 1897 at the University of Göttingen, these lamps were about twice as efficient as carbon-filament lamps and emitted a more "natural" light (more similar in spectrum to daylight). The lamps were quite successfully marketed for a time, although they eventually lost out to the more efficient tungsten-filament incandescent light ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Yttrium(III) Oxide
Yttrium oxide, also known as yttria, is Y2 O3. It is an air-stable, white solid substance. The thermal conductivity of yttrium oxide is 27 W/(m·K). Uses Phosphors Yttria is widely used to make Eu:YVO4 and Eu:Y2O3 phosphors that give the red color in color TV picture tubes. Yttria lasers Y2O3 is a prospective solid-state laser material. In particular, lasers with ytterbium as dopant allow the efficient operation both in continuous operation and in pulsed regimes. At high concentration of excitations (of order of 1%) and poor cooling, the quenching of emission at laser frequency and avalanche broadband emission takes place. (Yttria-based lasers are not to be confused with YAG lasers using yttrium aluminum garnet, a widely used crystal host for rare earth laser dopants). Gas Lighting The original use of the mineral yttria and the purpose of its extraction from mineral sources was as part of the process of making gas mantles and other products for turning the flames of artifici ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Calcia
Calcium oxide (CaO), commonly known as quicklime or burnt lime, is a widely used chemical compound. It is a white, caustic, alkaline, crystalline solid at room temperature. The broadly used term "''lime''" connotes calcium-containing inorganic materials, in which carbonates, oxides and hydroxides of calcium, silicon, magnesium, aluminium, and iron predominate. By contrast, ''quicklime'' specifically applies to the single chemical compound calcium oxide. Calcium oxide that survives processing without reacting in building products such as cement is called free lime. Quicklime is relatively inexpensive. Both it and a chemical derivative (calcium hydroxide, of which quicklime is the base anhydride) are important commodity chemicals. Preparation Calcium oxide is usually made by the thermal decomposition of materials, such as limestone or seashells, that contain calcium carbonate (CaCO3; mineral calcite) in a lime kiln. This is accomplished by heating the material to above ,Merck Ind ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oxide
An oxide () is a chemical compound that contains at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion of oxygen, an O2– (molecular) ion. with oxygen in the oxidation state of −2. Most of the Earth's crust consists of oxides. Even materials considered pure elements often develop an oxide coating. For example, aluminium foil develops a thin skin of Al2O3 (called a passivation layer) that protects the foil from further corrosion.Greenwood, N. N.; & Earnshaw, A. (1997). Chemistry of the Elements (2nd Edn.), Oxford:Butterworth-Heinemann. . Stoichiometry (the measurable relationship between reactants and chemical equations of a equation or reaction) Oxides are extraordinarily diverse in terms of stoichiometries and in terms of the structures of each stoichiometry. Most elements form oxides of more than one stoichiometry. A well known example is carbon monoxide and carbon dioxide.Greenwood, N. N.; & Earnshaw, A. (1997). Chemist ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zirconium Dioxide
Zirconium dioxide (), sometimes known as zirconia (not to be confused with zircon), is a white crystalline oxide of zirconium. Its most naturally occurring form, with a monoclinic crystalline structure, is the mineral baddeleyite. A dopant stabilized cubic structured zirconia, cubic zirconia, is synthesized in various colours for use as a gemstone and a diamond simulant. Production, chemical properties, occurrence Zirconia is produced by calcining zirconium compounds, exploiting its high thermostability.Ralph Nielsen "Zirconium and Zirconium Compounds" in Ullmann's Encyclopedia of Industrial Chemistry, 2005, Wiley-VCH, Weinheim. Structure Three phases are known: monoclinic below 1170 °C, tetragonal between 1170 °C and 2370 °C, and cubic above 2370 °C. The trend is for higher symmetry at higher temperatures, as is usually the case. A small percentage of the oxides of calcium or yttrium stabilize in the cubic phase. The very rare mineral tazher ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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