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A ceramic is any of the various hard, brittle, heat-resistant and
corrosion-resistant Corrosion is a Erosion, natural process that converts a refined metal into a more chemically stable form such as oxide, hydroxide, carbonate or sulfide. It is the gradual destruction of materials (usually a metal) by chemical and/or electrochem ...
materials made by shaping and then firing an inorganic, nonmetallic material, such as
clay Clay is a type of fine-grained natural soil File:Stagnogley.JPG, Surface-water-Gley soil, gley developed in glacial till, Northern Ireland. Soil is a mixture of organic matter, minerals, gases, liquids, and organisms that together support ...

clay
, at a high temperature. Common examples are
earthenware Earthenware is glazed or unglazed nonvitreous pottery Pottery is the process and the products of forming vessels and other objects with clay and other ceramic materials, which are fired at high temperatures to give them a hard, durable form ...

earthenware
,
porcelain Porcelain () is a material made by heating substances, generally including materials such as , in a to temperatures between . The strength, and translucence of porcelain, relative to other types of , arises mainly from and formation of the ...

porcelain
, and
brick A brick is a type of block used to build walls, pavements and other elements in masonry Masonry is the building of structures from individual units, which are often laid in and bound together by mortar Mortar may refer to: * Mortar (weap ...

brick
. The earliest ceramics made by humans were
pottery Pottery is the process and the products of forming vessels and other objects with and other materials, which are fired at high temperatures to give them a hard, durable form. Major types include , and . The place where such wares are mad ...

pottery
objects (''pots'' or ''vessels'') or
figurine A figurine (a diminutive form of the word ''figure'') or statuette is a small, three-dimensional sculpture ''lamassu 300px, ''Lamassu'' from Dur-Sharrukin. University of Chicago Oriental Institute. Syrian limestone Neo-Assyrian Period, c ...

figurine
s made from
clay Clay is a type of fine-grained natural soil File:Stagnogley.JPG, Surface-water-Gley soil, gley developed in glacial till, Northern Ireland. Soil is a mixture of organic matter, minerals, gases, liquids, and organisms that together support ...

clay
, either by itself or mixed with other materials like
silica Silicon dioxide, also known as silica, is an oxide An oxide () is a chemical compound A chemical compound is a chemical substance A chemical substance is a form of matter In classical physics and general chemistry, matter is any su ...
, hardened and
sintered image:LDClinkerScaled.jpg, Clinker (cement), Clinker nodules produced by sintering Sintering or frittage is the process of compacting and forming a solid mass of material by heat or pressure without melting it to the point of liquefaction. Sinte ...
in fire. Later, ceramics were glazed and fired to create smooth, colored surfaces, decreasing
porosity Porosity or void fraction is a measure of the void Void may refer to: Science, engineering, and technology * Void (astronomy), the spaces between galaxy filaments that contain no galaxies * Void (composites), a pore that remains unoccupied in a ...
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
semiconductor A semiconductor material has an value falling between that of a , such as metallic copper, and an , such as glass. Its falls as its temperature rises; metals behave in the opposite way. Its conducting properties may be altered in useful ways ...
s. The word "''
ceramic A ceramic is any of the various hard, brittle, heat-resistant and corrosion-resistant Corrosion is a natural process that converts a refined metal into a more chemically stable form such as oxide of rutile. Ti(IV) centers are grey; oxygen ce ...
''" comes from the
Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximately 10.7 million as of ...
word (), "of pottery" or "for pottery", from (), "potter's clay, tile, pottery". The earliest known mention of the root "ceram-" is the
Mycenaean Greek Mycenaean Greek is the most ancient attested form of the Greek language Greek (modern , romanized: ''Elliniká'', Ancient Greek, ancient , ''Hellēnikḗ'') is an independent branch of the Indo-European languages, Indo-European family of lan ...
, workers of ceramic written in
Linear B Linear B is a syllabic script that was used for writing Mycenaean Greek, the earliest attested form of Greek. The script predates the Greek alphabet The Greek alphabet has been used to write the Greek language since the late ninth or ...
syllabic script. The word ceramic can be used as an adjective to describe a material, product or process, or it may be used as a noun, either singular, or more commonly, as the plural noun "ceramics".


Materials

Ceramic material is an inorganic, non-metallic oxide, nitride, or carbide material. Some elements, such as
carbon Carbon (from la, carbo "coal") is a with the C and 6. It is lic and —making four s available to form s. It belongs to group 14 of the periodic table. Carbon makes up only about 0.025 percent of Earth's crust. Three occur naturally, ...

carbon
or
silicon Silicon is a chemical element with the Symbol (chemistry), symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic lustre, and is a Tetravalence, tetravalent metalloid and semiconductor. It is a member ...

silicon
, may be considered ceramics. Ceramic materials are brittle, hard, strong in compression, and weak in
shearing
shearing
and tension. They withstand chemical erosion that occurs in other materials subjected to acidic or caustic environments. Ceramics generally can withstand very high temperatures, ranging from 1,000 °C to 1,600 °C (1,800 °F to 3,000 °F). The
crystallinity Crystallinity refers to the degree of structural order in a solid Solid is one of the four fundamental states of matter (the others being liquid, gas and plasma). The molecules in a solid are closely packed together and contain the le ...
of ceramic materials varies widely. Most often, fired ceramics are either
vitrified 300px, A vitrification experiment, using molten glass. Vitrification (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area ar ...

vitrified
or semi-vitrified as is the case with earthenware,
stoneware Stoneware is a rather broad term for pottery or other ceramics fired at a relatively high temperature. A modern technical definition is a Vitrification#In ceramics, vitreous or semi-vitreous ceramic made primarily from stoneware clay or non-refrac ...
, and porcelain. Varying crystallinity and
electron The electron is a subatomic particle (denoted by the symbol or ) whose electric charge is negative one elementary charge. Electrons belong to the first generation (particle physics), generation of the lepton particle family, and are general ...

electron
composition in the ionic and covalent bonds cause most ceramic materials to be good thermal and electrical insulators (researched in
ceramic engineering Ceramic engineering is the science and technology of creating objects from inorganic, non-metallic materials. This is done either by the action of heat, or at lower temperatures using precipitation reactions from high-purity chemical solutions ...
). With such a large range of possible options for the composition/structure of a ceramic (nearly all of the elements, nearly all types of bonding, and all levels of crystallinity), the breadth of the subject is vast, and identifiable attributes (
hardness Hardness (antonym: softness) is a measure of the resistance to localized induced by either mechanical or . In general, different materials differ in their hardness; for example hard metals such as and are harder than soft metals such as and ...
,
toughness In materials science The Interdisciplinarity, interdisciplinary field of materials science, also commonly termed materials science and engineering, covers the design and discovery of new materials, particularly solids. The intellectual origin ...
,
electrical conductivity Electrical resistivity (also called specific electrical resistance or volume resistivity) is a fundamental property of a material that measures how strongly it resists electric current An electric current is a stream of charged particle In p ...
) are difficult to specify for the group as a whole. General properties such as high melting temperature, high hardness, poor conductivity, high moduli of elasticity, chemical resistance and low ductility are the norm, with known exceptions to each of these rules (
piezoelectric ceramics Piezoelectricity is the electric charge that accumulates in certain solid materials (such as crystals, certain ceramics, and biological matter such as bone, DNA and various proteins) in response to applied Stress (mechanics), mechanical stress. Th ...

piezoelectric ceramics
,
glass transition The glass–liquid transition, or glass transition, is the gradual and reversible transition in amorphous In condensed matter physics Condensed matter physics is the field of physics Physics (from grc, φυσική (ἐπιστήμη ...
temperature,
superconductive ceramics
superconductive ceramics
). Many composites, such as
fiberglass Fiberglass (American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. English, is the set of varieties of the English language native to the United States. Currently, American Englis ...
and
carbon fiber Carbon fiber reinforced polymer (American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. English, is the set of varieties of the English language native to the United States. Cur ...
, while containing ceramic materials are not considered to be part of the ceramic family. Highly oriented crystalline ceramic materials are not amenable to a great range of processing. Methods for dealing with them tend to fall into one of two categories – either make the ceramic in the desired shape, by reaction ''in situ'', or by "forming" powders into the desired shape, and then
sintering Clinker nodules produced by sintering Sintering or frittage is the process of compacting and forming a solid mass of material by heat or pressure without melting it to the point of liquefaction In materials science The interdisciplinary ...
to form a solid body.
Ceramic forming techniques A ceramic is any of the various hard, brittle, heat-resistant and corrosion-resistant materials made by shaping and then firing a nonmetallic mineral, such as clay, at a high temperature. Common examples are earthenware Earthenware is glazed ...
include shaping by hand (sometimes including a rotation process called "throwing"),
slip casting Slipcasting or slip casting is a ceramic forming techniques , ceramic forming technique for pottery and other ceramics, especially for shapes not easily made on a Potter's wheel, wheel. In slipcasting, a liquid clay body slip (ceramics), slip (u ...
,
tape castingTape casting (also called doctor blading and knife coating) is a casting Image:casting.jpg, upJudenplatz Holocaust Memorial (Nameless Library), by Rachel Whiteread. Concrete cast of books on library shelves turned inside out. Casting is a manufac ...

tape casting
(used for making very thin ceramic capacitors),
injection molding Injection moulding (U.S. spelling: injection molding) is a manufacturing process for producing parts by injecting molten material into a Molding (process), mould, or mold. Injection moulding can be performed with a host of materials mainly inc ...

injection molding
, dry pressing, and other variations. Many ceramics experts do not consider materials with
amorphous In condensed matter physics Condensed matter physics is the field of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science th ...

amorphous
(noncrystalline) character (i.e., glass) to be ceramics even though glassmaking involves several steps of the ceramic process and its mechanical properties are similar to ceramic materials. However, heat treatments can convert glass into a semi-crystalline material known as
glass-ceramic Glass-ceramics are polycrystal A crystallite is a small or even microscopic crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic struc ...
. Traditional ceramic raw materials include clay minerals such as
kaolinite Kaolinite ( ) is a clay mineral Clay minerals are , sometimes with variable amounts of , , s, s, and other s found on or near some s. Clay minerals form in the presence of water and have been important to life, and many theories of in ...

kaolinite
, whereas more recent materials include aluminum oxide, more commonly known as
alumina Aluminium oxide is a of and with the 23. It is the most commonly occurring of several , and specifically identified as aluminium(III) oxide. It is commonly called alumina and may also be called aloxide, aloxite, or alundum depending on part ...

alumina
. The modern ceramic materials, which are classified as advanced ceramics, include
silicon carbide Silicon carbide (SiC), also known as carborundum (), is a semiconductor containing silicon and carbon. It occurs in nature as the extremely rare mineral moissanite. Synthetic SiC powder has been mass-produced since 1893 for use as an abrasive. Gra ...

silicon carbide
and
tungsten carbide Tungsten carbide (chemical formula A chemical formula is a way of presenting information about the chemical proportions of s that constitute a particular or molecule, using symbols, numbers, and sometimes also other symbols, such as pa ...

tungsten carbide
. Both are valued for their abrasion resistance and hence find use in applications such as the wear plates of crushing equipment in mining operations. Advanced ceramics are also used in the medicine, electrical, electronics industries, and body armor.


History

Human beings appear to have been making their own ceramics for at least 26,000 years, subjecting clay and silica to intense heat to fuse and form ceramic materials. The earliest found so far were in southern central Europe and were sculpted figures, not dishes. The earliest known pottery was made by mixing animal products with clay and baked in kilns at up to 800°C. While actual pottery fragments have been found up to 19,000 years old, it was not until about ten thousand years later that regular pottery became common. An early people that spread across much of Europe is named after its use of pottery, the
Corded Ware culture#REDIRECT Corded Ware culture The Corded Ware culture comprises a broad archaeological horizon of Europe Europe is a continent A continent is one of several large landmasses. Generally identified by convention (norm), convention ra ...

Corded Ware culture
. These early
Indo-European The Indo-European languages are a language family A language family is a group of language A language is a structured system of communication Communication (from Latin ''communicare'', meaning "to share" or "to be in relation ...
peoples decorated their pottery by wrapping it with rope, while still wet. When the ceramics were fired, the rope burned off but left a decorative pattern of complex grooves on the surface. The invention of the wheel eventually led to the production of smoother, more even pottery using the wheel-forming technique, like the pottery wheel. Early ceramics were porous, absorbing water easily. It became useful for more items with the discovery of glazing techniques, coating pottery with silicon, bone ash, or other materials that could melt and reform into a glassy surface, making a vessel less pervious to water.


Archaeology

Ceramic artifacts have an important role in archaeology for understanding the culture, technology, and behavior of peoples of the past. They are among the most common artifacts to be found at an archaeological site, generally in the form of small fragments of broken pottery called
sherd This page is a glossary of archaeology Archaeology or archeology is the study of human activity through the recovery and analysis of material culture. Archaeology is often considered a branch of socio-cultural anthropology, but archaeologist ...
s. Processing of collected sherds can be consistent with two main types of analysis: technical and traditional. The traditional analysis involves sorting ceramic artifacts, sherds, and larger fragments into specific types based on style, composition, manufacturing, and morphology. By creating these typologies, it is possible to distinguish between different cultural styles, the purpose of the ceramic, and the technological state of the people among other conclusions. Besides, by looking at stylistic changes of ceramics over time is it possible to separate (seriate) the ceramics into distinct diagnostic groups (assemblages). A comparison of ceramic artifacts with known dated assemblages allows for a chronological assignment of these pieces. The technical approach to ceramic analysis involves a finer examination of the composition of ceramic artifacts and sherds to determine the source of the material and through this the possible manufacturing site. Key criteria are the composition of the clay and the temper used in the manufacture of the article under study: the temper is a material added to the clay during the initial production stage, and it is used to aid the subsequent drying process. Types of temper include shell pieces, granite fragments, and ground sherd pieces called 'grog'. Temper is usually identified by microscopic examination of the tempered material. Clay identification is determined by a process of refiring the ceramic and assigning a color to it using Munsell Soil Color notation. By estimating both the clay and temper compositions, and locating a region where both are known to occur, an assignment of the material source can be made. From the source assignment of the artifact, further investigations can be made into the site of manufacture.


Properties

The physical properties of any ceramic substance are a direct result of its crystalline structure and chemical composition.
Solid-state chemistry Solid-state chemistry, also sometimes referred as materials chemistry, is the study of the synthesis, structure, and properties of solid phase materials, particularly, but not necessarily exclusively of, non-molecular solids. It therefore has a str ...
reveals the fundamental connection between microstructure and properties, such as localized density variations, grain size distribution, type of porosity, and second-phase content, which can all be correlated with ceramic properties such as mechanical strength σ by the Hall-Petch equation,
hardness Hardness (antonym: softness) is a measure of the resistance to localized induced by either mechanical or . In general, different materials differ in their hardness; for example hard metals such as and are harder than soft metals such as and ...
,
toughness In materials science The Interdisciplinarity, interdisciplinary field of materials science, also commonly termed materials science and engineering, covers the design and discovery of new materials, particularly solids. The intellectual origin ...
,
dielectric constant The dielectric constant (or relative permittivity) is the permittivity, electric permeability of a material expressed as a ratio with the vacuum permittivity, electric permeability of a vacuum. A dielectric is an insulating material, and the diele ...
, and the
optical Optics is the branch of physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space and time, and the related entitie ...
properties exhibited by
transparent materials In the field of optics Optics is the branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies matter, its ...
.
CeramographyCeramography is the art and science of preparation, examination and evaluation of ceramic microstructures. Ceramography can be thought of as the metallography of ceramics. The microstructure is the structure level of approximately 0.1 to 100 Micromet ...
is the art and science of preparation, examination, and evaluation of ceramic microstructures. Evaluation and characterization of ceramic microstructures are often implemented on similar spatial scales to that used commonly in the emerging field of nanotechnology: from tens of ångstroms (Å) to tens of micrometers (µm). This is typically somewhere between the minimum wavelength of visible light and the resolution limit of the naked eye. The microstructure includes most grains, secondary phases, grain boundaries, pores, micro-cracks, structural defects, and hardness micro indentions. Most bulk mechanical, optical, thermal, electrical, and magnetic properties are significantly affected by the observed microstructure. The fabrication method and process conditions are generally indicated by the microstructure. The root cause of many ceramic failures is evident in the cleaved and polished microstructure. Physical properties which constitute the field of
materials science The interdisciplinary Interdisciplinarity or interdisciplinary studies involves the combination of two or more academic disciplines into one activity (e.g., a research project). It draws knowledge from several other fields like sociology, a ...
and
engineering Engineering is the use of scientific principles to design and build machines, structures, and other items, including bridges, tunnels, roads, vehicles, and buildings. The discipline of engineering encompasses a broad range of more speciali ...

engineering
include the following:


Mechanical properties

Mechanical properties are important in structural and building materials as well as textile fabrics. In modern
materials science The interdisciplinary Interdisciplinarity or interdisciplinary studies involves the combination of two or more academic disciplines into one activity (e.g., a research project). It draws knowledge from several other fields like sociology, a ...
, fracture mechanics is an important tool in improving the mechanical performance of materials and components. It applies the
physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space and time, and the related entities of energy and force. "Physical scie ...

physics
of stress and strain, in particular the theories of
elasticity Elasticity often refers to: *Elasticity (physics), continuum mechanics of bodies that deform reversibly under stress Elasticity may also refer to: Information technology * Elasticity (data store), the flexibility of the data model and the clu ...
and
plasticity Plasticity may refer to: Science * Plasticity (physics), in engineering and physics, the propensity of a solid material to undergo permanent deformation under load * Neuroplasticity, in neuroscience, how entire brain structures, and the brain its ...
, to the microscopic
crystallographic defects Crystallography is the experimental science of determining the arrangement of atoms in crystalline solids (see crystal structure In crystallography, crystal structure is a description of the ordered arrangement of atoms, ions or molecule F ...
found in real materials in order to predict the macroscopic mechanical failure of bodies.
Fractography. ''Hachures'' are the lines on fracture surface that can be traced back to the origin of the fracture. Fractography is the study of the fracture surfaces of materials. Fractographic methods are routinely used to determine the cause of failure in en ...
is widely used with fracture mechanics to understand the causes of failures and also verify the theoretical
failure Failure is the state or condition of not meeting a desirable or intended objective Objective may refer to: * Objective (optics), an element in a camera or microscope * ''The Objective'', a 2008 science fiction horror film * Objective pronoun ...

failure
predictions with real-life failures. Ceramic materials are usually
ionic Ionic or Ionian may refer to: Arts and entertainment * Ionic meter, a poetic metre in ancient Greek and Latin poetry * Ionian mode, a musical mode or a diatonic scale Places and peoples * Ionian, of or from Ionia, an ancient region in western An ...
or
covalent A covalent bond is a chemical bond A chemical bond is a lasting attraction between atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and take ...

covalent
bonded materials. A material held together by either type of bond will tend to
fracture Fracture is the separation of an object or material into two or more pieces under the action of stress (physics), stress. The fracture of a solid usually occurs due to the development of certain displacement discontinuity surfaces within the ...
before any
plastic deformation In engineering Engineering is the use of scientific principles to design and build machines, structures, and other items, including bridges, tunnels, roads, vehicles, and buildings. The discipline of engineering encompasses a broad ra ...
takes place, which results in poor
toughness In materials science The Interdisciplinarity, interdisciplinary field of materials science, also commonly termed materials science and engineering, covers the design and discovery of new materials, particularly solids. The intellectual origin ...
in these materials. Additionally, because these materials tend to be porous, the
pore Pore may refer to: Biology Animal biology and microbiology * Sweat pore Perspiration, also known as sweating, is the production of fluids secreted by the sweat glands in the skin Skin is the layer of usually soft, flexible outer tissue ...
s and other microscopic imperfections act as stress concentrators, decreasing the toughness further, and reducing the
tensile strength Ultimate tensile strength (UTS), often shortened to tensile strength (TS), ultimate strength, or F_\text within equations, is the maximum stress that a material can withstand while being stretched or pulled before breaking. In brittle tensi ...
. These combine to give
catastrophic failure A catastrophic failure is a sudden and total failure Failure is the state or condition of not meeting a desirable or intended objective Objective may refer to: * Objective (optics), an element in a camera or microscope * ''The Objective'', ...
s, as opposed to the more ductile
failure mode Failure causes are defects in design, process, quality, or part application, which are the underlying cause of a failure or which initiate a process which leads to failure. Where failure depends on the user of the product or process, then human erro ...
s of metals. These materials do show
plastic deformation In engineering Engineering is the use of scientific principles to design and build machines, structures, and other items, including bridges, tunnels, roads, vehicles, and buildings. The discipline of engineering encompasses a broad ra ...
. However, because of the rigid structure of crystalline material, there are very few available slip systems for
dislocation In materials science The interdisciplinary Interdisciplinarity or interdisciplinary studies involves the combination of two or more academic discipline An academic discipline or academic field is a subdivision of knowledge that is Edu ...

dislocation
s to move, and so they deform very slowly. To overcome the brittle behavior, ceramic material development has introduced the class of
ceramic matrix composite CMC shaft sleeves Ceramic matrix composites (CMCs) are a subgroup of composite material A composite material (also called a composition material or shortened to composite, which is the common name) is a material which is produced from two or mor ...
materials, in which ceramic fibers are embedded and with specific coatings are forming fiber bridges across any crack. This mechanism substantially increases the fracture toughness of such ceramics. Ceramic
disc brakes A disc brake is a type of brake A brake is a mechanical device A machine is a man-made Artificiality (the state of being artificial or man-made) is the state of being the product of intentional human manufacture, rather than occurring nat ...

disc brakes
are an example of using a ceramic matrix composite material manufactured with a specific process.


Ice-templating for enhanced mechanical properties

If ceramic is subjected to substantial mechanical loading, it can undergo a process called ice-templating, which allows some control of the
microstructure Microstructure is the very small scale structure of a material, defined as the structure of a prepared surface of material as revealed by an optical microscope above 25× magnification. The microstructure of a material (such as Metallography, m ...
of the ceramic product and therefore some control of the mechanical properties. Ceramic engineers use this technique to tune the mechanical properties to their desired application. Specifically,
strength Physical strength *Physical strength, as in people or animals *Hysterical strength, extreme strength occurring when people are in life-and-death situations *Superhuman strength, great physical strength far above human capability *A common attrib ...
is increased, when this technique is employed. Ice templating allows the creation of macroscopic pores in a unidirectional arrangement. The applications of this oxide strengthening technique are important for
solid oxide fuel cells
solid oxide fuel cells
and
water filtration A water filter removes impurities by lowering contamination of water Water (chemical formula H2O) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is ...
devices. To process a sample through ice templating, an aqueous
colloidal suspension A colloid is a mixture In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, molecules and ions: their composition, structure, properties, behavior ...

colloidal suspension
is prepared to contain the dissolved ceramic powder evenly dispersed throughout the colloid, for example
Yttria-stabilized zirconia Yttria-stabilized zirconia (YSZ) is a ceramic A ceramic is any of the various hard, brittle, heat-resistant and corrosion-resistant materials made by shaping and then firing a nonmetallic mineral, such as clay, at a high temperature. Common e ...
(YSZ). The solution is then cooled from the bottom to the top on a platform that allows for unidirectional cooling. This forces
ice Ice is water Water (chemical formula H2O) is an , transparent, tasteless, odorless, and , which is the main constituent of 's and the s of all known living organisms (in which it acts as a ). It is vital for all known forms of , eve ...

ice
crystals to grow in compliance with the unidirectional cooling and these ice crystals force the dissolved YSZ particles to the solidification front of the solid-liquid interphase boundary, resulting in pure ice crystals lined up unidirectionally alongside concentrated pockets of colloidal particles. The sample is then simultaneously heated and the pressure is reduced enough to force the ice crystals to sublimate and the YSZ pockets begin to anneal together to form macroscopically aligned ceramic microstructures. The sample is then further
sintered image:LDClinkerScaled.jpg, Clinker (cement), Clinker nodules produced by sintering Sintering or frittage is the process of compacting and forming a solid mass of material by heat or pressure without melting it to the point of liquefaction. Sinte ...
to complete the
evaporation Evaporation is a type of vaporization Vaporization (or vaporisation) of an element or compound is a phase transition from the liquid phase to vapor. There are two types of vaporization: evaporation and boiling. Evaporation is a surface phe ...

evaporation
of the residual water and the final consolidation of the ceramic microstructure. During ice-templating, a few variables can be controlled to influence the pore size and morphology of the microstructure. These important variables are the initial solids loading of the colloid, the cooling rate, the sintering temperature and duration, and the use of certain additives which can influence the microstructural morphology during the process. A good understanding of these parameters is essential to understanding the relationships between processing, microstructure, and mechanical properties of anisotropically porous materials.


Electrical properties


Semiconductors

Some ceramics are
semiconductor A semiconductor material has an value falling between that of a , such as metallic copper, and an , such as glass. Its falls as its temperature rises; metals behave in the opposite way. Its conducting properties may be altered in useful ways ...
s. Most of these are
transition metal oxides An oxide () is a chemical compound that contains at least one oxygen atom and one other chemical element, element in its chemical formula. "Oxide" itself is the dianion of oxygen, an O2– (molecular) ion. Metal oxides thus typically contain an a ...
that are II-VI semiconductors, such as
zinc oxide Zinc oxide is an inorganic compound In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behavior ...

zinc oxide
. While there are prospects of mass-producing blue
LED An LED A light-emitting diode (LED) is a semiconductor A semiconductor material has an Electrical resistivity and conductivity, electrical conductivity value falling between that of a Electrical conductor, conductor, such as metallic ...
s from zinc oxide, ceramicists are most interested in the electrical properties that show
grain boundary of a polycrystalline A crystallite is a small or even microscopic crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, for ...
effects. One of the most widely used of these is the varistor. These are devices that exhibit the property that resistance drops sharply at a certain
threshold voltage The threshold voltage, commonly abbreviated as Vth, of a field-effect transistor (FET) is the minimum gate-to-source voltage VGS (th) that is needed to create a conducting path between the source and drain terminals. It is an important scaling f ...
. Once the voltage across the device reaches the threshold, there is a breakdown of the electrical structure in the vicinity of the grain boundaries, which results in its
electrical resistance The electrical resistance of an object is a measure of its opposition to the flow of electric current. Its Multiplicative inverse, reciprocal quantity is , measuring the ease with which an electric current passes. Electrical resistance shares s ...
dropping from several megohms down to a few hundred
ohm The ohm (symbol: Ω) is the SI derived unit SI derived units are units of measurement ' Measurement is the number, numerical quantification (science), quantification of the variable and attribute (research), attributes of an object or event, ...
s. The major advantage of these is that they can dissipate a lot of energy, and they self-reset; after the voltage across the device drops below the threshold, its resistance returns to being high. This makes them ideal for
surge-protection
surge-protection
applications; as there is control over the threshold voltage and energy tolerance, they find use in all sorts of applications. The best demonstration of their ability can be found in
electrical substation A substation is a part of an electrical Electricity generation, generation, electric power transmission, transmission, and electric power distribution, distribution system. Substations transform voltage from high to low, or the reverse, or per ...

electrical substation
s, where they are employed to protect the infrastructure from
lightning Lightning is a naturally occurring electrostatic discharge Electrostatic discharge (ESD) is the sudden flow of electricity Electricity is the set of physical phenomena associated with the presence and motion Image:Leaving Yongsan ...

lightning
strikes. They have rapid response, are low maintenance, and do not appreciably degrade from use, making them virtually ideal devices for this application. Semiconducting ceramics are also employed as
gas sensor A gas detector is a device that detects the presence of gas Gas is one of the four fundamental states of matter In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Mo ...
s. When various gases are passed over a polycrystalline ceramic, its electrical resistance changes. With tuning to the possible gas mixtures, very inexpensive devices can be produced.


Superconductivity

Under some conditions, such as extremely low temperature, some ceramics exhibit
high-temperature superconductivity High-temperature superconductors (abbreviated high-c or HTS) are operatively defined as materials that behave as superconductors at temperatures above , the boiling point of liquid nitrogen Students preparing homemade dewar of liquid nit ...
. The reason for this is not understood, but there are two major families of superconducting ceramics.


Ferroelectricity and supersets

Piezoelectricity Piezoelectricity (, ) is the electric charge Electric charge is the physical property of matter that causes it to experience a force when placed in an electromagnetic field. Electric charge can be ''positive'' or ''negative'' (commonly carrie ...

Piezoelectricity
, a link between electrical and mechanical response, is exhibited by a large number of ceramic materials, including the quartz used to
measure time
measure time
in watches and other electronics. Such devices use both properties of piezoelectrics, using electricity to produce a mechanical motion (powering the device) and then using this mechanical motion to produce electricity (generating a signal). The unit of time measured is the natural interval required for electricity to be converted into mechanical energy and back again. The piezoelectric effect is generally stronger in materials that also exhibit
pyroelectricity Pyroelectricity (from the two Greek words ''pyr'' meaning fire, and electricity Electricity is the set of physical phenomena associated with the presence and motion Image:Leaving Yongsan Station.jpg, 300px, Motion involves a change in p ...
, and all pyroelectric materials are also piezoelectric. These materials can be used to inter-convert between thermal, mechanical, or electrical energy; for instance, after synthesis in a furnace, a pyroelectric crystal allowed to cool under no applied stress generally builds up a static charge of thousands of volts. Such materials are used in
motion sensor A motion detector is an electrical device that utilizes a sensor to detect nearby motion. Such a device is often integrated as a component of a system that automatically performs a task or alerts a user of motion in an area. They form a vital compo ...
s, where the tiny rise in temperature from a warm body entering the room is enough to produce a measurable voltage in the crystal. In turn, pyroelectricity is seen most strongly in materials that also display the
ferroelectric effectFerroelectricity is a characteristic of certain materials that have a Spontaneous process, spontaneous Polarization density, electric polarization that can be reversed by the application of an external electric field. All ferroelectrics are pyroelect ...
, in which a stable electric dipole can be oriented or reversed by applying an electrostatic field. Pyroelectricity is also a necessary consequence of ferroelectricity. This can be used to store information in
ferroelectric capacitorFerroelectric capacitor is a capacitor A capacitor is a device that stores electric charge in an electric field. It is a passivity (engineering), passive electronic component with two terminal (electronics), terminals. The effect of a capacit ...
s, elements of
ferroelectric RAM Ferroelectric RAM (FeRAM, F-RAM or FRAM) is a similar in construction to but using a layer instead of a layer to achieve non-volatility. FeRAM is one of a growing number of alternative technologies that offer the same functionality as . An ...
. The most common such materials are
lead zirconate titanate Lead zirconate titanate is an with the (0≤''x''≤1). Also called lead zirconium titanate, it is a ceramic material that shows a marked , meaning that the compound changes shape when an electric field is applied. It is used in a number of ...
and
barium titanate Barium titanate (BTO) is an inorganic compound In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, propertie ...
. Aside from the uses mentioned above, their strong piezoelectric response is exploited in the design of high-frequency
loudspeaker A loudspeaker (or ''speaker driver'', or most frequently just ''speaker'') is an Acoustical engineering#Electroacoustics, electroacoustic transducer, that is, a device that converts an electrical audio signal into a corresponding sound. A ''spe ...

loudspeaker
s, transducers for
sonar Sonar (sound navigation and ranging) is a technique that uses sound propagation (usually underwater, as in submarine navigation) to navigation, navigate, measure distances (ranging), communicate with or detect objects on or under the surface o ...

sonar
, and actuators for atomic force and
scanning tunneling microscope A scanning tunneling microscope (STM) is a type of microscope used for imaging surfaces at the atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and ...
s.


Positive thermal coefficient

Temperature increases can cause grain boundaries to suddenly become insulating in some semiconducting ceramic materials, mostly mixtures of
heavy metal Heavy metal may refer to: *Heavy metals, a loose category of relatively dense metals and metalloids **Toxic heavy metal, any heavy metal chemical element of environmental concern *Heavy metal music, a genre of rock music **Heavy metal genres *Hea ...
titanates. The critical transition temperature can be adjusted over a wide range by variations in chemistry. In such materials, current will pass through the material until
joule heating Joule heating, also known as resistive, resistance, or Ohmic heating, is the process by which the passage of an electric current An electric current is a stream of charged particle In physics Physics (from grc, φυσική (ἐπι ...
brings it to the transition temperature, at which point the circuit will be broken and current flow will cease. Such ceramics are used as self-controlled heating elements in, for example, the rear-window defrost circuits of automobiles. At the transition temperature, the material's
dielectric In electromagnetism Electromagnetism is a branch of physics involving the study of the electromagnetic force, a type of physical interaction that occurs between electric charge, electrically charged particles. The electromagnetic force i ...

dielectric
response becomes theoretically infinite. While a lack of temperature control would rule out any practical use of the material near its critical temperature, the dielectric effect remains exceptionally strong even at much higher temperatures. Titanates with critical temperatures far below room temperature have become synonymous with "ceramic" in the context of ceramic capacitors for just this reason.


Optical properties

Optically transparent materials
Optically transparent materials
focus on the response of a material to incoming light waves of a range of wavelengths.
Frequency selective optical filters
Frequency selective optical filters
can be utilized to alter or enhance the brightness and contrast of a digital image. Guided lightwave transmission via frequency selective
waveguides A waveguide is a structure that guides waves, such as electromagnetic wave Electromagnetism is a branch of physics involving the study of the electromagnetic force, a type of physical interaction that occurs between electric charge, electr ...
involves the emerging field of fiber
optics Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of optical instruments, instruments that use or Photodetector, detect it. Optics usually describes t ...

optics
and the ability of certain glassy compositions as a
transmission medium A transmission medium is a system or substance that can mediate the propagation of signal In signal processing Signal processing is an electrical engineering subfield that focuses on analysing, modifying, and synthesizing signals such ...
for a range of frequencies simultaneously (
multi-mode optical fiber A stripped multi-mode fiber Multi-mode optical fiber is a type of optical fiber An optical fiber (or fibre in British English British English (BrE) is the standard dialect of the English language English is a West Germanic ...
) with little or no
interference Interference is the act of interfering, invading, or poaching. Interference may also refer to: Communications * Interference (communication), anything which alters, modifies, or disrupts a message * Adjacent-channel interference, caused by extran ...
between competing
wavelengths In physics Physics is the that studies , its , its and behavior through , and the related entities of and . "Physical science is that department of knowledge which relates to the order of nature, or, in other words, to the regular su ...

wavelengths
or frequencies. This
resonant Resonance describes the phenomenon of increased amplitude The amplitude of a Periodic function, periodic Variable (mathematics), variable is a measure of its change in a single Period (mathematics), period (such as frequency, time or Wavelen ...
mode Mode ( la, modus meaning "manner, tune, measure, due measure, rhythm, melody") may refer to: Language * Grammatical mode In linguistics, grammatical mood is a Grammar, grammatical feature of verbs, used for signalling Modality (natural langua ...
of
energy In physics Physics is the that studies , its , its and behavior through , and the related entities of and . "Physical science is that department of knowledge which relates to the order of nature, or, in other words, to the regula ...

energy
and
data transmission Data transmission and data reception or, more broadly, data communication or digital communications is the transfer and reception of data Data (; ) are individual facts, statistics, or items of information, often numeric. In a more techn ...

data transmission
via electromagnetic (light)
wave propagation Wave propagation is any of the ways in which wave In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies matter, ...
, though low powered, is virtually lossless. Optical waveguides are used as components in
Integrated optical circuitA photonic integrated circuit (PIC) or integrated optical circuit is a device that integrates multiple (at least two) photonic functions and as such is similar to an electronic integrated circuit. The major difference between the two is that a photon ...
s (e.g.
light-emitting diodes A light-emitting diode (LED) is a semiconductor A semiconductor material has an value falling between that of a , such as metallic copper, and an , such as glass. Its falls as its temperature rises; metals behave in the opposite ...
, LEDs) or as the transmission medium in local and long haul
optical communication Optical communication, also known as optical telecommunication, is communication Communication (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was ...

optical communication
systems. Also of value to the emerging materials scientist is the sensitivity of materials to radiation in the thermal
infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior ...

infrared
(IR) portion of the
electromagnetic spectrum The electromagnetic spectrum is the range of frequency, frequencies (the spectrum) of electromagnetic radiation and their respective wavelengths and photon energy, photon energies. The electromagnetic spectrum covers electromagnetic waves with f ...

electromagnetic spectrum
. This heat-seeking ability is responsible for such diverse optical phenomena as
Night-vision soldiers pictured during the 2003 Iraq War The 2003 invasion of Iraq was the first stage of the Iraq War The Iraq WarThe conflict is also known as the Second Gulf War or the Third Gulf War by those who consider the Iran–Iraq War the ...
and IR
luminescence Luminescence is spontaneous emission of light Light or visible light is electromagnetic radiation within the portion of the electromagnetic spectrum that can be visual perception, perceived by the human eye. Visible light is usually defined ...

luminescence
. Thus, there is an increasing need in the
military A military, also known collectively as armed forces, is a heavily armed, highly organized force primarily intended for warfare War is an intense armed conflict between State (polity), states, governments, Society, societies, or pa ...

military
sector for high-strength, robust materials which have the capability to
transmit
transmit
light Light or visible light is electromagnetic radiation within the portion of the electromagnetic spectrum that is visual perception, perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nan ...

light
(
electromagnetic waves In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies matter, its Motion (physics), motion and behavior through ...

electromagnetic waves
) in the
visible Visibility is in meteorology, a measure of the distance at which an object or light can be seen. Visibility may also refer to: * Visual perception ** Naked-eye visibility * A measure of turbidity in water quality control * Interferometric visibili ...
(0.4 – 0.7 micrometers) and mid-
infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior ...

infrared
(1 – 5 micrometers) regions of the spectrum. These materials are needed for applications requiring
transparent Transparency, transparence or transparent most often refer to transparency and translucency, the physical property of allowing the transmission of light through a material. They may also refer to: Literal uses * Transparency (photography), a sti ...
armor, including next-generation high-speed
missile In military terminology, a missile is a missile guidance, guided airborne ranged weapon capable of self-propelled flight usually by a jet engine or rocket motor. Missiles are thus also called guided missiles or guided rockets (when in rocket f ...
s and pods, as well as protection against improvised explosive devices (IED). In the 1960s, scientists at General Electric (GE) discovered that under the right manufacturing conditions, some ceramics, especially
aluminium oxide Aluminium oxide is a chemical compound of aluminium and oxygen with the chemical formula 23. It is the most commonly occurring of several Aluminium oxide (compounds), aluminium oxides, and specifically identified as aluminium(III) oxide. It is ...

aluminium oxide
(alumina), could be made
translucent In the field of optics Optics is the branch of physics Physics is the that studies , its , its and behavior through , and the related entities of and . "Physical science is that department of knowledge which relates to the order ...
. These translucent materials were transparent enough to be used for containing the electrical
plasma Plasma or plasm may refer to: Science * Plasma (physics), one of the four fundamental states of matter * Plasma (mineral) or heliotrope, a mineral aggregate * Quark–gluon plasma, a state of matter in quantum chromodynamics Biology * Blood plasma ...
generated in high-
pressure Pressure (symbol: ''p'' or ''P'') is the force In physics, a force is an influence that can change the motion (physics), motion of an Physical object, object. A force can cause an object with mass to change its velocity (e.g. moving fr ...

pressure
sodium Sodium is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical eleme ...

sodium
street lamps. During the past two decades, additional types of transparent ceramics have been developed for applications such as nose cones for
heat-seeking 300px, A modern German Air Force IRIS-T infrared homing air-to-air missile Infrared homing is a Missile guidance#Passive homing, passive weapon guidance system which uses the infrared (IR) light emission from a target to track and follow it. Mis ...
missiles In military terminology, a missile is a guided airborne ranged weapon . English longbowmen figure prominently in the foreground at right where they drive away the French crossbow A crossbow is a ranged weapon using an elastic launching ...
,
window A window is an opening in a wall A wall is a structure and a surface that defines an area; carries a load; provides security Security is freedom from, or resilience against, potential Potential generally refers to a currently unrealize ...

window
s for fighter
aircraft An aircraft is a vehicle that is able to flight, fly by gaining support from the Atmosphere of Earth, air. It counters the force of gravity by using either Buoyancy, static lift or by using the Lift (force), dynamic lift of an airfoil, or in ...

aircraft
, and
scintillation counter A scintillation counter is an instrument for detecting and measuring ionizing radiation by using the excitation effect of incident radiation on a Scintillation (physics), scintillating material, and detecting the resultant light pulses. It consis ...
s for computed
tomography File:Sagittal brain MRI.jpg, thumbnail, Median plane Sagittal plane, sagittal tomography of the head by magnetic resonance imaging. Tomography is image, imaging by sections or sectioning through the use of any kind of penetrating wave. The method i ...
scanners. Other ceramic materials, generally requiring greater purity in their make-up than those above, include forms of several chemical compounds, including: #
Barium titanate Barium titanate (BTO) is an inorganic compound In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, propertie ...
: (often mixed with
strontium titanate Strontium titanate is an oxide of rutile. Ti(IV) centers are grey; oxygen centers are red. Notice that oxygen forms three bonds to titanium and titanium forms six bonds to oxygen. An oxide () is a chemical compound that contains at least one oxy ...
) displays
ferroelectricityFerroelectricity is a characteristic of certain materials that have a spontaneous electric polarization that can be reversed by the application of an external electric field. All ferroelectrics are pyroelectric, with the additional property that t ...
, meaning that its mechanical, electrical, and thermal responses are c # Sialon ( Silicon Aluminium Oxynitride) has high strength; resistance to thermal shock, chemical and wear resistance, and low density. These ceramics are used in non-ferrous molten metal handling, weld pins, and the chemical industry. #Silicon carbide (SiC) is used as a susceptor in microwave furnaces, a commonly used abrasive, and as a refraction (metallurgy), refractory material. #Silicon nitride (Si3nitrogen, N4) is used as an abrasive powder. #Magnesium silicide, Steatite (magnesium silicates) is used as an electrical insulator. #Titanium carbide Used in space shuttle re-entry shields and scratchproof watches. #Uranium oxide (uranium, UO2), used as nuclear fuel, fuel in nuclear reactors. #Yttrium barium copper oxide (Ybarium, Ba2copper, Cu3oxygen, O7−x), another high temperature Superconductivity, superconductor. #Zinc oxide (zinc, ZnO), which is a
semiconductor A semiconductor material has an value falling between that of a , such as metallic copper, and an , such as glass. Its falls as its temperature rises; metals behave in the opposite way. Its conducting properties may be altered in useful ways ...
, and used in the construction of varistors. #Zirconium dioxide (zirconia), which in pure form undergoes many phase transition, phase changes between room temperature and practical
sintering Clinker nodules produced by sintering Sintering or frittage is the process of compacting and forming a solid mass of material by heat or pressure without melting it to the point of liquefaction In materials science The interdisciplinary ...
temperatures, can be chemically "stabilized" in several different forms. Its high oxygen ion conductivity recommends it for use in fuel cells and automotive oxygen sensors. In another variant, metastable structures can impart Fracture toughness, transformation toughening for mechanical applications; most ceramic knife blades are made of this material. Partially stabilised zirconia (PSZ) is much less brittle than other ceramics and is used for metal forming tools, valves and liners, abrasive slurries, kitchen knives and bearings subject to severe abrasion.


Products


By usage

For convenience, ceramic products are usually divided into four main types; these are shown below with some examples: #Structural, including
brick A brick is a type of block used to build walls, pavements and other elements in masonry Masonry is the building of structures from individual units, which are often laid in and bound together by mortar Mortar may refer to: * Mortar (weap ...

brick
s, pipe (material), pipes, Flooring, floor and roof tiles #refractory, Refractories, such as kiln linings, gas fire radiants, steel and glass making crucibles #Whitewares, including tableware, cookware, wall tiles, pottery products and sanitary ware #Technical, also known as engineering, advanced, special, and fine ceramics. Such items include: ##gas burner nozzles ##Ballistic vest, ballistic protection, vehicle armor ##nuclear fuel uranium oxide pellets ##Implant (medicine), biomedical implants ##coatings of jet engine turbine blades ##Ceramic matrix composite gas turbine parts ##Reinforced carbon–carbon ceramic disc brakes ##
missile In military terminology, a missile is a missile guidance, guided airborne ranged weapon capable of self-propelled flight usually by a jet engine or rocket motor. Missiles are thus also called guided missiles or guided rockets (when in rocket f ...
nose cones ##bearing (mechanical) ##tiles used in the Space Shuttle program


Ceramics made with clay

Frequently, the raw materials of modern ceramics do not include clays. Those that do are classified as follows: #Earthenware, fired at lower temperatures than other types #Stoneware, Vitrification#In ceramics, vitreous or semi-vitreous #Porcelain, which contains a high content of kaolin #Bone china


Classification

Ceramics can also be classified into three distinct material categories: # Oxides:
alumina Aluminium oxide is a of and with the 23. It is the most commonly occurring of several , and specifically identified as aluminium(III) oxide. It is commonly called alumina and may also be called aloxide, aloxite, or alundum depending on part ...

alumina
, beryllia, ceria, zirconia # Non-oxides: carbide, boride, nitride, silicide # Composite materials: particulate reinforced, Ceramic matrix composite, fiber reinforced, combinations of oxides and nonoxides. Each one of these classes can be developed into unique material properties.


Applications

#Knife blades: blade of a ceramic knife will stay sharp for much longer than that of a steel knife, although it is more brittle and susceptible to breaking. #Disk brake, Carbon-ceramic brake disks: for vehicles are resistant to brake fade at high temperatures. #"Advanced Composite armor , composite ceramic and metal matrices" have been designed for most modern armoured fighting vehicles because they offer superior penetrating resistance against shaped charges (High explosive anti-tank, HEAT rounds) and kinetic energy penetrators. #"Ceramics such as
alumina Aluminium oxide is a of and with the 23. It is the most commonly occurring of several , and specifically identified as aluminium(III) oxide. It is commonly called alumina and may also be called aloxide, aloxite, or alundum depending on part ...

alumina
and boron carbide" have been used in bulletproof vest, ballistic armored vests to repel high-velocity rifle fire. Such plates are known commonly as Small Arms Protective Insert, small arms protective inserts, or SAPIs. Similar material is used to protect the Cockpit (aviation), cockpits of some military airplanes, because of the low weight of the material. #Ceramics can be used in place of steel for ball bearing, ball bearings. Their higher hardness means they are much less susceptible to wear and typically last for triple the lifetime of a steel part. They also deform less under load, meaning they have less contact with the bearing retainer walls and can roll faster. In very high-speed applications, heat from friction during rolling can cause problems for metal bearings, which are reduced by the use of ceramics. Ceramics are also more chemically resistant and can be used in wet environments where steel bearings would rust. In some cases, their electricity-insulating properties may also be valuable in bearings. Two drawbacks to ceramic bearings are a significantly higher cost and susceptibility to damage under shock loads. #In the early 1980s, Toyota researched production of an adiabatic internal combustion engine, engine using ceramic components in the hot gas area. The ceramics would have allowed temperatures of over 1650°C. The expected advantages would have been lighter materials and a smaller cooling system (or no need for one at all), leading to a major weight reduction. The expected increase of fuel efficiency of the engine (caused by the higher temperature, as shown by Carnot heat engine, Carnot's theorem) could not be verified experimentally; it was found that the heat transfer on the hot ceramic cylinder walls was higher than the transfer to a cooler metal wall as the cooler gas film on the metal surface works as a thermal insulator. Thus, despite all of these desirable properties, such engines have not succeeded in production because of costs for the ceramic components and the limited advantages. (Small imperfections in the ceramic material with its low fracture toughness lead to cracks, which can lead to potentially dangerous equipment failure.) Such engines are possible in laboratory settings, but mass production is not feasible with current technology. #Work is being done in developing ceramic parts for gas turbine heat engine, engines. Currently, even blades made of superalloy, advanced metal alloys used in the engines' hot section require cooling and careful limiting of operating temperatures. Turbine engines made with ceramics could operate more efficiently, giving aircraft greater range and payload for a set amount of fuel. #Recent advances have been made in ceramics which include bioceramics, such as dental implants and synthetic bones. Hydroxyapatite, the natural mineral component of bone, has been made synthetically from several biological and chemical sources and can be formed into ceramic materials. Orthopedic implants coated with these materials bond readily to bone and other tissues in the body without rejection or inflammatory reactions so are of great interest for gene delivery and tissue engineering scaffolds. Most hydroxyapatite ceramics are very porous and lack mechanical strength, and are used to coat metal orthopedic devices to aid in forming a bond to bone or as bone fillers. They are also used as fillers for orthopedic plastic screws to aid in reducing inflammation and increase the absorption of these plastic materials. Work is being done to make strong, fully dense nanocrystalline hydroxyapatite ceramic materials for orthopedic weight bearing devices, replacing foreign metal and plastic orthopedic materials with a synthetic, but naturally occurring bone mineral. Ultimately, these ceramic materials may be used as bone replacements or with the incorporation of protein collagens, synthetic bones. #Durable actinide-containing ceramic materials have many applications such as in nuclear fuels for burning excess Pu and in chemically-inert sources of alpha irradiation for power supply of unmanned space vehicles or to produce electricity for microelectronic devices. Both use and disposal of radioactive actinides require their immobilization in a durable host material. Nuclear waste long-lived radionuclides such as actinides are immobilized using chemically-durable crystalline materials based on polycrystalline ceramics and large single crystals. #High-tech ceramic is used in watchmaking for producing watch cases. The material is valued by watchmakers for its lightweight, scratch resistance, durability, and smooth touch. International Watch Company, IWC is one of the brands that initiated the use of ceramic in watchmaking.


See also

* * * * * * Pottery fracture


References


Further reading

*


External links


Dolni Vestonice Venus
Oldest knew ceramic statuette of a nude female figure dated to 29,000–25,000 BP (Gravettian industry). Czech Republic
The Gardiner Museum
– The only museum in Canada entirely devoted to ceramics

* [http://www.azom.com/details.asp?ArticleID=2123 Advanced Ceramics] – The Evolution, Classification, Properties, Production, Firing, Finishing and Design of Advanced Ceramics
Cerame-Unie, aisbl
– The European Ceramic Industry Association
Ceramics Science and Technology
{{Authority control Ceramics,