The earliest ceramics made by humans were fired clay bricks used for building house walls and other structures. Otherpottery objects such as pots, vessels, vases andfigurines were made fromclay, either by itself or mixed with other materials likesilica, hardened bysintering in fire. Later, ceramics wereglazed and fired to create smooth, colored surfaces, decreasingporosity through the use of glassy, amorphous ceramic coatings on top of the crystalline ceramic substrates.[3] Ceramics now include domestic, industrial, and building products, as well as a wide range of materials developed for use in advanced ceramic engineering, such assemiconductors.
The wordceramic comes from theAncient Greek wordκεραμικός (keramikós), meaning "of or forpottery"[4] (from κέραμος (kéramos)'potter's clay, tile, pottery').[5] The earliest known mention of the rootceram- is theMycenaean Greekke-ra-me-we, workers of ceramic, written inLinear B syllabic script.[6] The wordceramic 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 theplural nounceramics.[7]
Silicon nitride rocket thruster. Left: Mounted in test stand. Right: Being tested with H2/O2 propellants.
Ceramic material is aninorganic,metallicoxide,nitride, orcarbide material. Some elements, such ascarbon orsilicon, may be considered ceramics. Ceramic materials are brittle, hard, strong in compression, and weak inshearing and tension. They withstand the 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).
A low magnificationSEM micrograph of an advanced ceramic material. The properties of ceramics make fracturing an important inspection method.
Thecrystallinity of ceramic materials varies widely. Most often, fired ceramics are eithervitrified or semi-vitrified, as is the case with earthenware,stoneware, and porcelain. Varying crystallinity andelectron composition in the ionic and covalent bonds cause most ceramic materials to be good thermal andelectrical insulators (researched inceramic engineering). 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,toughness,electrical conductivity) are difficult to specify for the group as a whole. General properties such as high melting temperature, high hardness, poor conductivity, highmoduli of elasticity, chemical resistance, and low ductility are the norm,[8] with known exceptions to each of these rules (piezoelectric ceramics, lowglass transition temperature ceramics,superconductive ceramics).
Composites such asfiberglass andcarbon fiber, while containing ceramic materials, are not considered to be part of the ceramic family.[9]
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 making the ceramic in the desired shape by reactionin situ or "forming" powders into the desired shape and thensintering to form a solid body.Ceramic forming techniques include shaping by hand (sometimes including a rotation process called "throwing"),slip casting,tape casting (used for making very thin ceramic capacitors),injection molding, dry pressing, and other variations.
Many ceramics experts do not consider materials with anamorphous (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 those of ceramic materials. However, heat treatments can convert glass into a semi-crystalline material known asglass-ceramic.[10]
Traditional ceramic raw materials include clay minerals such askaolinite, whereas more recent materials include aluminium oxide, more commonly known asalumina. Modern ceramic materials, which are classified as advanced ceramics, includesilicon carbide andtungsten carbide. Both are valued for their abrasion resistance and are therefore used in applications such as the wear plates of crushing equipment in mining operations. Advanced ceramics are also used in the medical, electrical, electronics, and armor industries.
Earliest known ceramics are theGravettian figurines that date to 29,000–25,000 BC.
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.[11] The earliest known pottery was made by mixing animal products with clay and firing it at up to 800 °C (1,500 °F). While pottery fragments have been found up to 19,000 years old, it was not until about 10,000 years later that regular pottery became common. An early people that spread across much of Europe is named after its use of pottery: theCorded Ware culture. These earlyIndo-European peoples decorated their pottery by wrapping it with rope while it was still wet. When the ceramics were fired, the rope burned off but left a decorative pattern of complex grooves on the surface.
Corded-Ware culture pottery from 2500 BC
The invention of the wheel eventually led to the production of smoother, more even pottery using the wheel-forming (throwing) technique, like thepottery wheel. Early ceramics were porous, absorbing water easily. It became useful for more items with the discovery ofglazing techniques, which involved 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.
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 calledsherds. The 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 in ceramics over time, it is 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.[12]
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 thetemper used in the manufacture of the article under study: the temper is a material added to the clay during the initial production stage and is used to aid the subsequent drying process. Types of temper includeshell 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 usingMunsell 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. Based on the source assignment of the artifact, further investigations can be made into the site of manufacture.
The physical properties of any ceramic substance are a direct result of its crystalline structure and chemical composition.Solid-state chemistry 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,toughness,dielectric constant, and theoptical properties exhibited bytransparent materials.
Ceramography 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: fromnanometers 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 ofmaterials science andengineering include the following:
Mechanical properties are important in structural and building materials as well as textile fabrics. In modernmaterials science, fracture mechanics is an important tool in improving the mechanical performance of materials and components. It applies thephysics ofstress andstrain, in particular the theories ofelasticity andplasticity, to the microscopiccrystallographic defects found in real materials in order to predict the macroscopic mechanical failure of bodies.Fractography is widely used with fracture mechanics to understand the causes of failures and also verify the theoreticalfailure predictions with real-life failures.
Ceramic materials are usuallyionic orcovalent bonded materials. A material held together by either type of bond will tend tofracture before anyplastic deformation takes place, which results in poortoughness in these materials. Additionally, because these materials tend to be porous, thepores and other microscopic imperfections act asstress concentrators, decreasing the toughness further, and reducing thetensile strength. These combine to givecatastrophic failures, as opposed to the more ductilefailure modes of metals.
These materials do showplastic deformation. However, because of the rigid structure of crystalline material, there are very few available slip systems fordislocations to move, and so they deform very slowly.
To overcome the brittle behavior, ceramic material development has introduced the class ofceramic matrix composite 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. Ceramicdisc brakes are an example of using a ceramic matrix composite material manufactured with a specific process.
Scientists are working on developing ceramic materials that can withstand significant deformation without breaking. A first such material that can deform in room temperature was found in 2024.[13]
If a ceramic is subjected to substantial mechanical loading, it can undergo a process calledice-templating, which allows some control of themicrostructure 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, thestrength 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 forsolid oxide fuel cells andwater filtration devices.[14]
To process a sample through ice templating, an aqueouscolloidal suspension is prepared to contain the dissolved ceramic powder evenly dispersed throughout the colloid,[clarification needed] for exampleyttria-stabilized zirconia (YSZ). The solution is then cooled from the bottom to the top on a platform that allows for unidirectional cooling. This forces ice crystals to grow in compliance with the unidirectional cooling, and these ice crystals force the dissolved YSZ particles to the solidification front[clarification needed] of the solid-liquid interphase boundary, resulting in pure ice crystals lined up unidirectionally alongside concentrated pockets of colloidal particles. The sample is then heated and at the same the pressure is reduced enough to force the ice crystals tosublime and the YSZ pockets begin toanneal together to form macroscopically aligned ceramic microstructures. The sample is then furthersintered to complete theevaporation of the residual water and the final consolidation of the ceramic microstructure.[citation needed]
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.[15]
Some ceramics aresemiconductors. Most of these aretransition metal oxides that are II-VI semiconductors, such aszinc oxide. While there are prospects of mass-producing bluelight-emitting diodes (LED) from zinc oxide, ceramicists are most interested in the electrical properties that showgrain boundary 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 certainthreshold voltage. Once the voltage across the device reaches the threshold, there is abreakdown of the electrical structure[clarification needed] in the vicinity of the grain boundaries, which results in itselectrical resistance dropping from several megohms down to a few hundredohms. 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 forsurge-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 inelectrical substations, where they are employed to protect the infrastructure fromlightning 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 asgas sensors. 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.
Under some conditions, such as extremely low temperatures, some ceramics exhibithigh-temperature superconductivity (in superconductivity, "high temperature" means above 30 K). The reason for this is not understood, but there are two major families of superconducting ceramics.
Piezoelectricity, a link between electrical and mechanical response, is exhibited by a large number of ceramic materials, including the quartz used tomeasure 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 exhibitpyroelectricity, 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 inmotion sensors, 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 theferroelectric effect, 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 inferroelectric capacitors, elements offerroelectric RAM.
Temperature increases can cause grain boundaries to suddenly become insulating in some semiconducting ceramic materials, mostly mixtures ofheavy metaltitanates. The critical transition temperature can be adjusted over a wide range by variations in chemistry. In such materials, current will pass through the material untiljoule heating 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'sdielectric 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.
Thus, there is an increasing need in themilitary sector for high-strength, robust materials which have the capability to transmitlight (electromagnetic waves) in thevisible (0.4 – 0.7 micrometers) and mid-infrared (1 – 5 micrometers) regions of the spectrum. These materials are needed for applications requiringtransparent armor, including next-generation high-speedmissiles and pods, as well as protection against improvised explosive devices (IED).
In the 1960s, scientists atGeneral Electric (GE) discovered that under the right manufacturing conditions, some ceramics, especiallyaluminium oxide (alumina), could be madetranslucent. These translucent materials were transparent enough to be used for containing the electricalplasma generated in high-pressuresodium street lamps. During the past two decades, additional types of transparent ceramics have been developed for applications such as nose cones forheat-seekingmissiles,windows for fighteraircraft, andscintillation counters for computedtomography scanners. Other ceramic materials, generally requiring greater purity in their make-up than those above, include forms of several chemical compounds, including:
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.
Zirconium dioxide (zirconia), which in pure form undergoes manyphase changes between room temperature and practicalsintering temperatures, can be chemically "stabilized" in several different forms. Its high oxygenion conductivity recommends it for use infuel cells and automotiveoxygen sensors. In another variant,metastable structures can imparttransformation toughening for mechanical applications; mostceramic 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.[16]
Kitchen knife with a ceramic bladeTechnical ceramic used as a durable top material on adiving watch bezel insert
Knife blades: the blade of aceramic knife will stay sharp for much longer than that of a steel knife, although it is more brittle and susceptible to breakage.
Ceramicball bearings can be used in place of steel. Their greater hardness results in lower susceptibility to wear. Ceramic bearings typically last triple the lifetime of steel bearings. They deform less than steel under load, resulting in less contact with the bearing retainer walls and lower friction. In very high-speed applications, heat fromfriction causes more problems for metal bearings than ceramic bearings. Ceramics are chemically resistant to corrosion and are preferred for environments where steel bearings would rust. In some applications their electricity-insulating properties are advantageous. Drawbacks to ceramic bearings include significantly higher cost, susceptibility to damage under shock loads, and the potential to wear steel parts due to ceramics' greater hardness.
In the early 1980sToyota researched production of anadiabaticengine using ceramic components in the hot gas area. The use of ceramics would have allowed temperatures exceeding 1650 °C. Advantages would include lighter materials and a smaller cooling system (or no cooling system at all), leading to major weight reduction. The expected increase offuel efficiency (due to higher operating temperatures, demonstrated inCarnot's theorem) could not be verified experimentally. It was found that heat transfer on the hot ceramic cylinder wall was greater than the heat transfer to a cooler metal wall. This is because the cooler gas film on a metal surface acts as athermal insulator. Thus, despite the desirable properties of ceramics, prohibitive production costs and limited advantages have prevented widespread ceramic engine component adoption. In addition, small imperfections in ceramic material along with lowfracture toughness can lead to cracking and potentially dangerous equipment failure. Such engines are possible experimentally, but mass production is not feasible with current technology.[citation needed]
Experiments with ceramic parts forgas turbineengines are being conducted. Currently, even blades made ofadvanced metal alloys used in the engines' hot section require cooling and careful monitoring of operating temperatures. Turbine engines made with ceramics could operate more efficiently, providing for greater range and payload.
Recent advances have been made in ceramics which includebioceramics such as dental implants and synthetic bones.Hydroxyapatite, the major mineral component of bone, has been made synthetically from several biological and chemical components 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 reaction. They are of great interest for gene delivery andtissue engineering scaffolding. Most hydroxyapatite ceramics are quite porous and lack mechanical strength and are therefore used solely 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 replacement, or with the incorporation of proteincollagens, the manufacture of synthetic bones.
Applications for actinide-containing ceramic materials include nuclear fuels for burning excess plutonium (Pu), or a chemically inert source of alpha radiation in power supplies for uncrewed space vehicles or microelectronic devices. Use and disposal of radioactive actinides require immobilization in a durable host material. Long half-life radionuclides such as actinide are immobilized using chemically durable crystalline materials based on polycrystalline ceramics and large single crystals.[20]
High-tech ceramics are used for producing watch cases. The material is valued by watchmakers for its light weight, scratch resistance, durability, and smooth touch.IWC is one of the brands that pioneered the use of ceramic in watchmaking.[21]
Ceramics are used in the design of mobile phone bodies due to their high hardness, resistance to scratches, and ability to dissipate heat.[22] Ceramic's thermal management properties help in maintaining optimal device temperatures during heavy use enhancing performance. Additionally, ceramic materials can supportwireless charging[23] and offer better signal transmission compared to metals, which can interfere withantennas.[24] Companies likeApple andSamsung have incorporated ceramic in their devices.[25][26]
Ceramics made ofsilicon carbide are used inpump and valve components because of theircorrosion resistance characteristics.[27] It is also used innuclear reactors as fuel cladding materials due to their ability to withstandradiation andthermal stress.[28] Other uses of Silicon carbide ceramics include paper manufacturing,ballistics, chemical production, and as pipe system components.[29]
Ceramic chemistry – Science and technology of creating objects from inorganic, non-metallic materialsPages displaying short descriptions of redirect targets
Ceramic engineering – Science and technology of creating objects from inorganic, non-metallic materials
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^Wen, Haibing; Li, Jiayuan; Yang, Lei; Tong, Xiangqian (2022). "Feasibility Study on Wireless Power Transfer for AUV with Novel Pressure-Resistant Ceramic Materials".2022 International Power Electronics Conference (IPEC-Himeji 2022- ECCE Asia). pp. 182–185.doi:10.23919/IPEC-Himeji2022-ECCE53331.2022.9806898.ISBN978-4-8868-6425-3.
^Boecker, Wolfgang; Kruener, Hartmut (1994). "Silicon Carbide and Silicon Nitride Ceramics for High Performance Structural Applications: Development Status and Potential". In Sakaki, H. (ed.).Superconductors, Surfaces and Superlattices. Elsevier. pp. 865–973.ISBN9781483283821.
^Deng, Yangbin; Qiu, Bowen (2020). "Research on performance enhancement of nuclear fuel with SiC cladding by using high thermal conductivity fuels".Progress in Nuclear Energy.124.doi:10.1016/j.pnucene.2020.103330.
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