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CeramicFrom Wikipedia, the free encyclopedia

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Fixed Partial Denture, or "Bridge"

18th century (Qing dynasty) Chineseporcelain vase

A ceramic is an inorganic, non-metallicsolid prepared by the action ofheat and subsequentcooling.[1] Ceramic materials may have acrystalline or partly crystalline structure, or may beamorphous, i.e., aglass. As most common ceramics are crystalline, the definition of ceramic isoften restricted to inorganic crystalline materials, as opposed to the non-crystalline glasses.

The earliest ceramics werepotteryobjects made fromclay, either by itself or mixed with othermaterials. Ceramics now includes domestic, industrial and building products andart objects. Inthe 20th century new ceramic materials were developed for use in advanced ceramic engineering,for example, in semiconductors.

The word "ceramic" comes from the Greekword (keramikos) meaning pottery, whichis said to derive from the Indo-European word ker, meaning heat.[2][3] "Ceramic" may be used asan adjective describing a material, product or process; or as a singular noun, or, more commonly,as a plural noun, "ceramics".[4]

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1 Types of ceramic products

1.1 Examples of whiteware ceramics

1.2 Classification of technical ceramics

2 Other applications of ceramics

3 Types of ceramic materials

3.1 Crystalline ceramics

3.2 Non-crystalline ceramics

4 References

5 See also

6 External links

[edit] Types of ceramic products

For convenience ceramic products are usually divided into four sectors, and these are shownbelow with some examples:

Structural, includingbricks,pipes, floorand roof tiles

Refractories, such as kiln linings, gas fire radiants, steeland glass making crucibles

Whitewares, including tableware, wall tiles, pottery products, and sanitary ware

Technical, is also known as Engineering, Advanced, Special, and in Japan, FineCeramics. Such items include tiles used in theSpace Shuttle program, gas burnernozzles,ballistic protection, nuclear fuel uranium oxide pellets,bio-medical implants,jet engineturbine blades, and missile nose cones. Frequently the raw materials do not include clays.[5]

[edit] Examples of whiteware ceramics

Bone china

Earthenware, which is often made from clay, quartz and feldspar.

Porcelain, which are often made from kaolin

Stoneware

[edit] Classification of technical ceramics

Technical ceramics can also be classified into three distinct material categories:

Oxides: Alumina,zirconia

Non-oxides:Carbides,borides,nitrides,silicides

Composites: Particulate reinforced, combinations of oxides and non-oxides.

Each one of these classes can develop unique material properties

[edit] Other applications of ceramics

http://en.wikipedia.org/w/index.php?title=Ceramic&action=edit&section=1http://en.wikipedia.org/wiki/Brickhttp://en.wikipedia.org/wiki/Pipe_(material)http://en.wikipedia.org/wiki/Pipe_(material)http://en.wikipedia.org/wiki/Floorhttp://en.wikipedia.org/wiki/Roof_tilehttp://en.wikipedia.org/wiki/Refractoryhttp://en.wikipedia.org/wiki/Refractoryhttp://en.wikipedia.org/wiki/Kilnhttp://en.wikipedia.org/wiki/Steelhttp://en.wikipedia.org/wiki/Steelhttp://en.wikipedia.org/wiki/Tablewarehttp://en.wikipedia.org/wiki/Space_Shuttle_programhttp://en.wikipedia.org/wiki/Space_Shuttle_programhttp://en.wikipedia.org/wiki/Nozzlehttp://en.wikipedia.org/wiki/Nozzlehttp://en.wikipedia.org/wiki/Ballistic_vesthttp://en.wikipedia.org/wiki/Implant_(medicine)http://en.wikipedia.org/wiki/Implant_(medicine)http://en.wikipedia.org/wiki/Implant_(medicine)http://en.wikipedia.org/wiki/Jet_enginehttp://en.wikipedia.org/wiki/Turbinehttp://en.wikipedia.org/wiki/Missilehttp://en.wikipedia.org/w/index.php?title=Ceramic&action=edit&section=2http://en.wikipedia.org/wiki/Bone_chinahttp://en.wikipedia.org/wiki/Earthenwarehttp://en.wikipedia.org/wiki/Quartzhttp://en.wikipedia.org/wiki/Feldsparhttp://en.wikipedia.org/wiki/Porcelainhttp://en.wikipedia.org/wiki/Porcelainhttp://en.wikipedia.org/wiki/Kaolinhttp://en.wikipedia.org/wiki/Kaolinhttp://en.wikipedia.org/wiki/Stonewarehttp://en.wikipedia.org/w/index.php?title=Ceramic&action=edit&section=3http://en.wikipedia.org/wiki/Oxidehttp://en.wikipedia.org/wiki/Aluminahttp://en.wikipedia.org/wiki/Zirconiahttp://en.wikipedia.org/wiki/Zirconiahttp://en.wikipedia.org/wiki/Carbidehttp://en.wikipedia.org/wiki/Carbidehttp://en.wikipedia.org/wiki/Boridehttp://en.wikipedia.org/wiki/Nitridehttp://en.wikipedia.org/wiki/Nitridehttp://en.wikipedia.org/wiki/Silicidehttp://en.wikipedia.org/wiki/Silicidehttp://en.wikipedia.org/wiki/Mixturehttp://en.wikipedia.org/w/index.php?title=Ceramic&action=edit&section=4http://en.wikipedia.org/w/index.php?title=Ceramic&action=edit&section=1http://en.wikipedia.org/wiki/Brickhttp://en.wikipedia.org/wiki/Pipe_(material)http://en.wikipedia.org/wiki/Floorhttp://en.wikipedia.org/wiki/Roof_tilehttp://en.wikipedia.org/wiki/Refractoryhttp://en.wikipedia.org/wiki/Kilnhttp://en.wikipedia.org/wiki/Steelhttp://en.wikipedia.org/wiki/Tablewarehttp://en.wikipedia.org/wiki/Space_Shuttle_programhttp://en.wikipedia.org/wiki/Nozzlehttp://en.wikipedia.org/wiki/Ballistic_vesthttp://en.wikipedia.org/wiki/Implant_(medicine)http://en.wikipedia.org/wiki/Jet_enginehttp://en.wikipedia.org/wiki/Turbinehttp://en.wikipedia.org/wiki/Missilehttp://en.wikipedia.org/w/index.php?title=Ceramic&action=edit&section=2http://en.wikipedia.org/wiki/Bone_chinahttp://en.wikipedia.org/wiki/Earthenwarehttp://en.wikipedia.org/wiki/Quartzhttp://en.wikipedia.org/wiki/Feldsparhttp://en.wikipedia.org/wiki/Porcelainhttp://en.wikipedia.org/wiki/Kaolinhttp://en.wikipedia.org/wiki/Stonewarehttp://en.wikipedia.org/w/index.php?title=Ceramic&action=edit&section=3http://en.wikipedia.org/wiki/Oxidehttp://en.wikipedia.org/wiki/Aluminahttp://en.wikipedia.org/wiki/Zirconiahttp://en.wikipedia.org/wiki/Carbidehttp://en.wikipedia.org/wiki/Boridehttp://en.wikipedia.org/wiki/Nitridehttp://en.wikipedia.org/wiki/Silicidehttp://en.wikipedia.org/wiki/Mixturehttp://en.wikipedia.org/w/index.php?title=Ceramic&action=edit&section=4

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Ceramics are used in the manufacture of knives. The blade of a ceramic knife will staysharp for much longer than that of a steel knife, although it is more brittle and can besnapped by dropping it on a hard surface.

Ceramics such as alumina andboron carbide have been used inballistic armored veststorepel large-caliberrifle fire. Such plates are known commonly as small-arms protective

inserts (SAPI). Similar material is used to protect cockpits of some military airplanes,because of the low weight of the material.

Ceramic balls can be used to replace steel in ball bearings. Their higher hardness meansthat they are much less susceptible to wear and can offer more than triple lifetimes. Theyalso deform less under load meaning they have less contact with the bearing retainerwalls and can roll faster. In very high speed applications, heat from friction during rollingcan cause problems for metal bearings; problems which are reduced by the use ofceramics. Ceramics are also more chemically resistant and can be used in wetenvironments where steel bearings would rust. The major drawback to using ceramics is asignificantly higher cost. In many cases their electrically insulating properties may alsobe valuable in bearings.

In the early 1980s, Toyotaresearched production of an adiabaticceramic engine whichcan run at a temperature of over 6000F (3300C). Ceramic engines do not require acooling system and hence allow a major weight reduction and therefore greater fuelefficiency. Fuel efficiencyof the engine is also higher at high temperature, as shown byCarnot's theorem. In a conventional metallic engine, much of the energy released fromthe fuel must be dissipated as waste heatin order to prevent a meltdown of the metallicparts. Despite all of these desirable properties, such engines are not in production becausethe manufacturing of ceramic parts in the requisite precision and durability is difficult.Imperfection in the ceramic leads to cracks, which can lead to potentially dangerousequipment failure. Such engines are possible in laboratory settings, but mass-productionis not feasible with current technology.

Work is being done in developing ceramic parts forgas turbineengines. Currently, evenblades made ofadvanced metal alloysused in the engines' hot section require cooling andcareful limiting of operating temperatures. Turbine engines made with ceramics couldoperate more efficiently, giving aircraft greater range and payload for a set amount offuel.

Recently, there have been advances in ceramics which include bio-ceramics, such asdental implants and synthetic bones. Hydroxyapatite, the natural mineral component ofbone, has been made synthetically from a number of biological and chemical sources andcan be formed into ceramic materials. Orthopedic implants made from these materialsbond readily to bone and other tissues in the body without rejection or inflammatoryreactions. Because of this, they are of great interest for gene delivery andtissue

engineering scaffolds. Most hydroxyapatite ceramics are very porous and lackmechanical strength and are used to coat metal orthopedic devices to aid in forming abond to bone or as bone fillers. They are also used as fillers for orthopedic plastic screwsto aid in reducing the inflammation and increase absorption of these plastic materials.Work is being done to make strong, fully dense nano crystalline hydroxyapatite ceramicmaterials for orthopedic weight bearing devices, replacing foreign metal and plasticorthopedic materials with a synthetic, but naturally occurring, bone mineral. Ultimately

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these ceramic materials may be used as bone replacements or with the incorporation ofprotein collagens, synthetic bones.

High-tech ceramic is used in watchmaking for producing watch cases. The material isvalued by watchmakers for its light weight, scratch-resistance, durability and smoothtouch. IWC is one of the brands that initiated the use of ceramic in watchmaking. The

case of the IWC 2007 Top Gun edition of the Pilot's WatchDouble chronograph iscrafted in high-tech black ceramic.[6]

[edit] Types of ceramic materialsA ceramic material is often understood as restricted to inorganic crystalline oxide material. It issolid and inert. Ceramic materials are brittle, hard, strong in compression, weak in shearing andtension. They withstand chemical erosion that occurs in an acidic or caustic environment.Ceramics generally can withstand very high temperatures such as temperatures that range from1,000C to 1,600C (1,800F to 3,000F). Exceptions include inorganic materials that do notinclude oxygen such as silicon carbide orsilicon nitride. A glass is often not understood as aceramic because of its amorphous (non-crystalline) character. However, glass making involves

several steps of the ceramic process and its mechanical properties are similar to ceramicmaterials.

Traditional ceramic raw materials include clay minerals such as kaolinite, whereas more recentmaterials include aluminium oxide, more commonly known as alumina. The modern ceramicmaterials, which are classified as advanced ceramics, include silicon carbide and tungstencarbide. Both are valued for their abrasion resistance, and hence find use in applications such asthe wear plates of crushing equipment in mining operations. Advanced ceramics are also used inthe medicine, electrical and electronics industries.

[edit] Crystalline ceramics

Crystalline ceramic materials are not amenable to a great range of processing. Methods fordealing with them tend to fall into one of two categories - either make the ceramic in the desiredshape, by reaction in situ, or by "forming" powders into the desired shape, and then sintering toform a solid body. Ceramic forming techniques include shaping by hand (sometimes including arotation process called "throwing"), slip casting,tape casting (used for making very thin ceramiccapacitors, etc.), injection moulding, dry pressing, and other variations. (See alsoCeramicforming techniques. Details of these processes are described in the two books listed below.) Afew methods use a hybrid between the two approaches.

[edit] Non-crystalline ceramics

Non-crystalline ceramics, being glasses, tend to be formed from melts. The glass is shaped wheneither fully molten, by casting, or when in a state of toffee-like viscosity, by methods such asblowing to a mold. If later heat-treatments cause this class to become partly crystalline, the

resulting material is known as a glass-ceramic.

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