A ceramic is an inorganic Traditionally, inorganic compounds are considered to be of a mineral, not biological origin. Complementarily, most organic compounds are traditionally viewed as being of biological origin. Over the past century, the precise classification of inorganic vs organic compounds has become less important to scientists, primarily because the majority of, non-metallic Nonmetal, or non-metal, is a term used in chemistry when classifying the chemical elements. On the basis of their general physical and chemical properties, every element in the periodic table can be termed either a metal or a nonmetal. solid Solid is one of the major states of matter. It is characterized by structural rigidity and resistance to changes of shape or volume. Unlike a liquid, a solid object does not flow to take on the shape of its container, nor does it expand to fill the entire volume available to it like a gas does. The atoms in a solid are tightly bound to each other, prepared by the action of heat In physics and thermodynamics, heat is the process of energy transfer from one body or system to another due to thermal contact, which in turn is defined as an energy transfer to a body in any other way than due to work performed on the body and subsequent cooling.[1] Ceramic materials may have a crystalline A crystal or crystalline solid is a solid material, whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions. The scientific study of crystals and crystal formation is crystallography. The process of crystal formation via mechanisms of crystal growth is called or partly crystalline structure, or may be amorphous An "amorphous solid" is a solid in which there is no long-range order of the positions of the atoms. . Most classes of solid materials can be found or prepared in an amorphous form. For instance, common window glass is an amorphous solid, many polymers (such as polystyrene) are amorphous, and even junkfoods such as cotton candy are (e.g., a glass Glass is an amorphous solid material. Glasses are typically brittle, and often optically transparent. Glass is commonly used for windows, bottles, and eyewear; examples of glassy materials include soda-lime glass, borosilicate glass, acrylic glass, sugar glass, Muscovy-glass, and aluminium oxynitride. The term glass developed in the late Roman). Because most common ceramics are crystalline, the definition of ceramic is often restricted to inorganic crystalline materials, as opposed to the non-crystalline glasses.
The earliest ceramics were pottery Pottery is the ceramic ware made by potters. The place where such wares are made is also called a pottery . Pottery can also refer to the material of which the potteryware is made. Major types of pottery include earthenware, stoneware and porcelain. Pottery is one of the oldest human technologies and art-forms, and remains a major industry today objects made from clay Clay is a naturally occurring material composed primarily of fine-grained minerals. Clay deposits are mostly composed of clay minerals, a subtype of phyllosilicate minerals, which impart plasticity and harden when fired or dried; they also may contain variable amounts of water trapped in the mineral structure by polar attraction. Organic materials, either by itself or mixed with other materials, hardened in fire. Later ceramics were glazed and fired to create a colored, smooth surface. Ceramics now include domestic, industrial and building products and art objects In art history, ceramics and ceramic art mean art objects such as figures, tiles, and tableware made from clay and other raw materials by the process of pottery. Some ceramic products are regarded as fine art, while others are regarded as decorative, industrial or applied art objects, or as artifacts in archaeology. They may be made by one. In the 20th century, new ceramic materials Ceramic materials are inorganic, non-metallic materials and things made from them. They may be crystalline or partly crystalline. They are formed by the action of heat and subsequent cooling. Clay was one of the earliest materials used to produce ceramics, but many different ceramic materials are now used in domestic, industrial and building were developed for use in advanced 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. The term includes the purification of raw materials, the study and production of the chemical compounds; for example, in semiconductors A semiconductor is a material that has an electrical conductivity due to flowing electrons which is intermediate in magnitude between that of a conductor and an insulator. This means roughly in the range 103 to 10−8 siemens per centimeter. Devices made from semiconductor materials are the foundation of modern electronics, including radio,.
The word ceramic comes from the Greek Greek , an independent branch of the Indo-European family of languages, is the language of the Greeks. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. In its ancient form, it is the language of classical ancient Greek literature and the New Testament of word "κεραμικός" (keramikos), "of pottery" or "for pottery",[2] from "κέραμος" (keramos), "potter's clay, tile, pottery"[3] which is said to derive from the Indo-European word *cheros (unattested), meaning heat.[4][5] The earliest mention on the word "ceramic" is the Mycenaean Greek Mycenaean is the most ancient attested form of the Greek language, spoken on the Greek mainland and on Crete in the 16th to 12th centuries BC, before the hypothesised Dorian invasion which was often cited as the terminus post quem for the coming of the Greek language to Greece. The language is preserved in inscriptions in Linear B, a script first ke-ra-me-we, "workers of ceramics", written in Linear b Linear B is a syllabic script that was used for writing Mycenaean Greek, an early form of Greek. It predated the Greek alphabet by several centuries and seems to have died out with the fall of Mycenaean civilization. Most of the tablets inscribed in Linear B were found in Knossos, Cydonia, Pylos, Thebes and Mycenae. The succeeding period, known as syllabic script.[6] Ceramic may be used as an adjective describing a material, product or process; or as a singular noun, or, more commonly, as a plural noun, ceramics.[7]
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Types of ceramic products
For convenience, ceramic products are usually divided into four sectors; these are shown below with some examples:
- Structural, including bricks A brick is a block of ceramic material used in masonry construction, usually laid using various kinds of mortar, pipes A pipe is round tubular section or hollow cylinder used mainly to convey media. It can also be used for structural applications. In layman's terms the appellations pipe and tube are almost interchangeable, but in industry and engineering discipline the terms are uniquely defined. Depending on the applicable standard to which it is manufactured,, floor Flooring is the general term for a permanent covering of a floor, or for the work of installing such a floor covering. Floor covering is a term to generically describe any finish material applied over a floor structure to provide a walking surface. Both terms are used interchangeably but floor covering refers more to loose-laid materials and roof tiles A tile is a manufactured piece of hard-wearing material such as ceramic, stone, metal, or even glass. Tiles are generally used for covering roofs, floors, walls, showers, or other objects such as tabletops. Alternatively, tile can sometimes refer to similar units made from lightweight materials such as perlite, wood, and mineral wool, typically
- Refractories A refractory material is one that retains its strength at high temperatures. ASTM C71 defines refractories as "non-metallic materials having those chemical and physical properties that make them applicable for structures, or as components of systems, that are exposed to environments above 1,000 °F ", such as kiln Kilns are an essential part of the manufacture of all ceramics, which, by definition, require heat treatment, often at high temperature. During this process, chemical and physical reactions occur which cause the material to be permanently altered. In the case of pottery, clay materials are shaped, dried and then fired in a kiln. The final linings, gas fire radiants, steel Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten. Carbon and other elements act as a hardening agent, preventing and glass making crucibles
- Whitewares, including tableware Tableware or Table Appointments includes the dishes, sauce boats, glassware, and cutlerys used to set a table for eating a meal. The nature, variety, and number of objects varies from culture to culture, and may vary from meal to meal, wall tiles, pottery products, and sanitary ware
- Technical, is also known as Engineering, Advanced, Special, and in Japan, Fine Ceramics. Such items include tiles used in the Space Shuttle program NASA's Space Shuttle, officially called Space Transportation System , is the United States government's current manned launch vehicle. The winged Space Shuttle orbiter is launched vertically, usually carrying five to seven astronauts (although eight have been carried) and up to 50,000 lb (22 700 kg) of payload into low earth orbit. When its, gas burner nozzles A nozzle is a mechanical device designed to control the direction or characteristics of a fluid flow as it exits an enclosed chamber or pipe via an orifice, ballistic protection A ballistic vest, bulletproof vest or bullet-resistant vest is an item of personal armor that helps absorb the impact from firearm-fired projectiles and shrapnel from explosions, and is worn on the torso. Soft vests are made from many layers of woven or laminated fibers and can be capable of protecting the wearer from small caliber handgun and, nuclear fuel uranium oxide pellets, bio-medical implants An implant is a medical device manufactured to replace a missing biological structure, support a damaged biological structure, or enhance an existing biological structure. Medical implants are man-made devices, in contrast to a transplant, which is a transplanted biomedical tissue. The surface of implants that contact the body might be made of a, jet engine A jet engine is a reaction engine that discharges a fast moving jet of fluid to generate thrust by jet propulsion and in accordance with Newton's laws of motion. This broad definition of jet engines includes turbojets, turbofans, rockets, ramjets, pulse jets and pump-jets. In general, most jet engines are internal combustion engines but non- turbine A turbine is a rotary engine that extracts energy from a fluid flow and converts it into useful work blades, and missile In common military parlance, the word missile describes a powered, guided munition that travels through the air or space, whilst the word rocket describes a powered, unguided munition. Unpowered, guided munitions are known as guided bombs. Powered munitions that travel through water are called torpedoes. A common further sub-division is to nose cones. Frequently the raw materials do not include clays.[8]
Examples of whiteware ceramics
- Earthenware Earthenware is a common ceramic material, which is used extensively for pottery tableware and decorative objects. Although body formulations vary between countries and even between individual makers, a generic composition is 25% ball clay, 28% kaolin, 32% quartz, and 15% feldspar. Earthenware is one of the oldest materials used in pottery. While, which is often made from clay, quartz Quartz is the second most abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2 and feldspar Feldspars crystallize from magma in both intrusive and extrusive igneous rocks, as veins, and are also present in many types of metamorphic rock. Rock formed almost entirely of calcic plagioclase feldspar is known as anorthosite. Feldspars are also found in many types of sedimentary rock.
- Stoneware "Stoneware, which, though dense, impermeable and hard enough to resist scratching by a steel point, differs from porcelain because it is more opaque, and normally only partially vitrified. It may be vitreous or semi-vitreous. It is usually coloured grey or brownish because of impurities in the clay used for its manufacture, and is normally
- Porcelain Porcelain is a ceramic material made by heating raw materials, generally including clay in the form of kaolin, in a kiln to temperatures between 1,200 °C and 1,400 °C (2,552 °F). The toughness, strength, and translucence of porcelain arise mainly from the formation of glass and the mineral mullite within the fired body at these high, which are often made from kaolin Kaolinite is a clay mineral, part of the group of industrial minerals, with the chemical composition Al2Si2O54. It is a layered silicate mineral, with one tetrahedral sheet linked through oxygen atoms to one octahedral sheet of alumina octahedra. Rocks that are rich in kaolinite are known as china clay, white clay, or kaolin
- Bone china Bone china is a type of porcelain that is composed of bone ash, feldspathic material and kaolin. It has been defined as 'ware with a translucent body containing a minimum of 30% of phosphate derived from animal bone and calculated calcium phosphate. Developed by English potter Josiah Spode, bone china is known for its high levels of whiteness and
Classification of technical ceramics
Technical ceramics can also be classified into three distinct material categories:
- Oxides An oxide is a chemical compound containing at least one oxygen atom as well as at least one other element.[citation needed] Most of the Earth's crust consists of oxides. Oxides result when elements are oxidized by oxygen in air. Combustion of hydrocarbons affords the two principal oxides of carbon, carbon monoxide and carbon dioxide. Even: Alumina Aluminium oxide is the family of inorganic compounds with the chemical formula Al2O3. It is an amphoteric oxide and is commonly referred to as alumina, corundum as well as many other names, reflecting its widespread occurrence in nature and industry. Its most significant use is in the production of aluminium metal, although it is also used as an, zirconia Zirconium dioxide , sometimes known as zirconia (not to be confused with zircon), is a white crystalline oxide of zirconium. Its most naturally occurring form, with a monoclinic crystalline structure, is the rare mineral, baddeleyite. The high temperature cubic crystalline form, called 'cubic zirconia', is rarely found in nature as mineral
- Non-oxides: Carbides In chemistry, a carbide is a compound composed of carbon and a less electronegative element. Carbides can be generally classified by chemical bonding type as follows: salt-like, (ii) covalent compounds, (iii) interstitial compounds, and (iv) "intermediate" transition metal carbides. Examples include calcium carbide, silicon carbide,, borides In chemistry a boride is a chemical compound between boron and a less electronegative element. This is a very large group of compounds that are generally high melting and are not ionic in nature. Some borides exhibit very useful physical properties. The term boride is also loosely applied to compounds such as B12As2 that is often referred to as, nitrides In chemistry, a nitride is a compound of nitrogen with a less electronegative element where nitrogen has an oxidation state of −3. Nitrides are a large class of compounds with a wide range of properties and applications, silicides Silicon is more electropositive than carbon. Silicides are structurally closer to borides than to carbides
- Composites In chemistry, a mixture is a material system made up by two or more different substances which are together but are not combined chemically. Mixture refers to the physical combination of two or more substances the identities of which are retained. The molecules of two or more different substances are mixed in the form of alloys, solutions,: Particulate reinforced, combinations of oxides and non-oxides.
Each one of these classes can develop unique material properties because ceramics tend to be crystalline.
Other applications of ceramics
- Ceramics are used in the manufacture of knives. The blade of a ceramic knife A ceramic knife is a knife made out of very hard ceramic, often zirconium oxide . These knives are generally produced by compacting Zirconia powder using high pressure presses which apply a pressure of around 300 tons to produce blade shaped blanks. These blanks are very brittle and fragile which can be shattered by a slight blow and special will stay sharp for much longer than that of a steel knife, although it is more brittle and can be snapped by dropping it on a hard surface.
- Ceramics are increasingly used in motor sports, where a series of durable and lightweight insulatory coatings have become necessary, for example on exhaust manifolds In automotive engineering, an intake manifold or inlet manifold is the part of an engine that supplies the fuel/air mixture to the cylinders. An exhaust manifold or header collects the exhaust gases from multiple cylinders into one pipe. The word manifold comes from the Old English word manigfeald and refers to the folding together of multiple.
- Ceramics such as alumina Aluminium oxide is the family of inorganic compounds with the chemical formula Al2O3. It is an amphoteric oxide and is commonly referred to as alumina, corundum as well as many other names, reflecting its widespread occurrence in nature and industry. Its most significant use is in the production of aluminium metal, although it is also used as an and boron carbide Boron carbide is an extremely hard ceramic material used in tank armor, bulletproof vests, and numerous industrial applications. With a hardness of 9.3 on the mohs scale, it is one of the hardest materials known, behind cubic boron nitride and diamond have been used in ballistic armored vests to repel large-calibre rifle fire. Such plates are known commonly as Small Arms Protective Inserts (SAPI). Similar material is used to protect cockpits of some military airplanes, because of the low weight of the material.
- Ceramic balls can be used to replace steel in ball bearings. Their higher hardness means that they are much less susceptible to wear and can offer more than triple lifetimes. 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; problems 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 many cases their electrically insulating properties may also be valuable in bearings. The two major drawbacks to using ceramics is a significantly higher cost, and susceptibility to damage under shock loads.
- In the early 1980s, Toyota researched production of an adiabatic ceramic engine which can run at a temperature of over 6000 °F (3300 °C). Ceramic engines are made of lighter materials and do not require a cooling system and hence allow a major weight reduction. Fuel efficiency of the engine is also higher at high temperature, as shown by Carnot's theorem. In a conventional metallic engine, much of the energy released from the fuel must be dissipated as waste heat in order to prevent a meltdown of the metallic parts. Despite all of these desirable properties, such engines are not in production because the manufacturing of ceramic parts in the requisite precision and durability is difficult. Imperfection in the ceramic leads 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.[citation needed]
- Work is being done in developing ceramic parts for gas turbine engines. Currently, even blades made of 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.
- Recently, there have been advances in ceramics which include bio-ceramics, such as dental implants and synthetic bones. Hydroxyapatite, the natural mineral component of bone, has been made synthetically from a number of biological and chemical sources and can be formed into ceramic materials. Orthopedic implants made from these materials bond readily to bone and other tissues in the body without rejection or inflammatory reactions. Because of this, they 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 the inflammation and increase absorption of these plastic materials. Work is being done to make strong, fully dense nano crystalline 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.
- High-tech ceramic is used in watchmaking 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 initiated the use of ceramic in watchmaking. The case of the IWC 2007 Top Gun edition of the Pilot's Watch Double chronograph is crafted in black ceramic.[9]
Types of ceramic materials
A ceramic material is often understood as restricted to inorganic crystalline oxide material. It is solid and inert. Ceramic materials are brittle, hard, strong in compression, weak in shearing and tension. They withstand chemical erosion that occurs in other materials subjected to acidic or caustic environment. Ceramics generally can withstand very high temperatures such as temperatures that range from 1,000 °C to 1,600 °C (1,800 °F to 3,000 °F). Exceptions include inorganic materials that do not include oxygen such as silicon carbide or silicon nitride. A glass is often not understood as a ceramic because of its amorphous (non-crystalline) character. However, glass making involves several steps of the ceramic process and its mechanical properties are similar to ceramic materials.
Traditional ceramic raw materials include clay minerals such as kaolinite, whereas more recent materials include aluminium oxide, more commonly known as alumina. The modern ceramic materials, which are classified as advanced ceramics, include silicon carbide and 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 and electronics industries.
Crystalline ceramics
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 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, etc.), injection moulding, dry pressing, and other variations. (See also Ceramic forming techniques. Details of these processes are described in the two books listed below.) A few methods use a hybrid between the two approaches.
Non-crystalline ceramics
Non-crystalline ceramics, being glasses, tend to be formed from melts. The glass is shaped when either fully molten, by casting, or when in a state of toffee-like viscosity, by methods such as blowing to a mold. If later heat-treatments cause this glass to become partly crystalline, the resulting material is known as a glass-ceramic.
See also
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Fri, 03 Sep 2010 21:58:59 GM
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