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71-401: The traditional shape of the molds used for pig iron ingots is a branching structure formed in sand , with many individual ingots at right angles to a central channel or "runner", resembling a litter of piglets being nursed by a sow . When the metal had cooled and hardened, the smaller ingots (the "pigs") were simply broken from the runner (the "sow"), hence the name "pig iron". As pig iron

142-580: A chemical element such as iron ; an alloy such as stainless steel ; or a molecular compound such as polymeric sulfur nitride . The general science of metals is called metallurgy , a subtopic of materials science ; aspects of the electronic and thermal properties are also within the scope of condensed matter physics and solid-state chemistry , it is a multidisciplinary topic. In colloquial use materials such as steel alloys are referred to as metals, while others such as polymers, wood or ceramics are nonmetallic materials . A metal conducts electricity at

213-578: A plasma (physics) is a metallic conductor and the charged particles in a plasma have many properties in common with those of electrons in elemental metals, particularly for white dwarf stars. Metals are relatively good conductors of heat , which in metals is transported mainly by the conduction electrons. At higher temperatures the electrons can occupy slightly higher energy levels given by Fermi–Dirac statistics . These have slightly higher momenta ( kinetic energy ) and can pass on thermal energy. The empirical Wiedemann–Franz law states that in many metals

284-435: A semiconducting metalloid such as boron has an electrical conductivity 1.5 × 10 S/cm. With one exception, metallic elements reduce their electrical conductivity when heated. Plutonium increases its electrical conductivity when heated in the temperature range of around −175 to +125 °C, with anomalously large thermal expansion coefficient and a phase change from monoclinic to face-centered cubic near 100  °C. There

355-454: A base metal as it is oxidized relatively easily, although it does not react with HCl. The term noble metal (also for elements) is commonly used in opposition to base metal . Noble metals are less reactive, resistant to corrosion or oxidation , unlike most base metals . They tend to be precious metals, often due to perceived rarity. Examples include gold, platinum, silver, rhodium , iridium, and palladium. In alchemy and numismatics ,

426-1012: A currency reserve, as with gold bars . Ingots are generally made of metal, either pure or alloy, heated past its melting point and cast into a bar or block using a mold chill method. A special case are polycrystalline or single crystal ingots made by pulling from a molten melt. Single crystal ingots (called boules ) of materials are grown (crystal growth) using methods such as the Czochralski process or Bridgeman technique . The boules may be either semiconductor (e.g. electronic chip wafers , photovoltaic cells ) or non-conducting inorganic compounds for industrial and jewelry use (e.g., synthetic ruby, sapphire). Single crystal ingots of metal are produced in similar fashion to that used to produce high purity semiconductor ingots, i.e. by vacuum induction refining. Single crystal ingots of engineering metals are of interest due to their very high strength due to lack of grain boundaries . The method of production

497-690: A few micrometres appear opaque, but gold leaf transmits green light. This is due to the freely moving electrons which reflect light. Although most elemental metals have higher densities than nonmetals , there is a wide variation in their densities, lithium being the least dense (0.534 g/cm ) and osmium (22.59 g/cm ) the most dense. Some of the 6d transition metals are expected to be denser than osmium, but their known isotopes are too unstable for bulk production to be possible Magnesium, aluminium and titanium are light metals of significant commercial importance. Their respective densities of 1.7, 2.7, and 4.5 g/cm can be compared to those of

568-443: A few—beryllium, chromium, manganese, gallium, and bismuth—are brittle. Arsenic and antimony, if admitted as metals, are brittle. Low values of the ratio of bulk elastic modulus to shear modulus ( Pugh's criterion ) are indicative of intrinsic brittleness. A material is brittle if it is hard for dislocations to move, which is often associated with large Burgers vectors and only a limited number of slip planes. A refractory metal

639-426: A larger contact area. Molds may be either solid "massive" design, sand cast (e.g. for pig iron), or water-cooled shells, depending upon heat transfer requirements. Ingot molds are tapered to prevent the formation of cracks due to uneven cooling. A crack or void formation occurs as the liquid to solid transition has an associated volume change for a constant mass of material. The formation of these ingot defects may render

710-511: A lower atomic number) by neutron capture , with the two main modes of this repetitive capture being the s-process and the r-process . In the s-process ("s" stands for "slow"), singular captures are separated by years or decades, allowing the less stable nuclei to beta decay , while in the r-process ("rapid"), captures happen faster than nuclei can decay. Therefore, the s-process takes a more-or-less clear path: for example, stable cadmium-110 nuclei are successively bombarded by free neutrons inside

781-581: A piece of relatively pure material, usually metal , that is cast into a shape suitable for further processing. In steelmaking , it is the first step among semi-finished casting products . Ingots usually require a second procedure of shaping, such as cold/hot working, cutting, or milling to produce a useful final product. Non-metallic and semiconductor materials prepared in bulk form may also be referred to as ingots, particularly when cast by mold based methods. Precious metal ingots can be used as currency (with or without being processed into other shapes), or as

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852-514: A real metal. In this respect they resemble degenerate semiconductors . This explains why the electrical properties of semimetals are partway between those of metals and semiconductors . There are additional types, in particular Weyl and Dirac semimetals . The classic elemental semimetallic elements are arsenic , antimony , bismuth , α- tin (gray tin) and graphite . There are also chemical compounds , such as mercury telluride (HgTe), and some conductive polymers . Metallic elements up to

923-407: A result of a neutron star merger, thereby increasing the abundance of elements heavier than helium in the interstellar medium . When gravitational attraction causes this matter to coalesce and collapse new stars and planets are formed . The Earth's crust is made of approximately 25% of metallic elements by weight, of which 80% are light metals such as sodium, magnesium, and aluminium. Despite

994-483: A role as investments and a store of value . Palladium and platinum, as of summer 2024, were valued at slightly less than half the price of gold, while silver is substantially less expensive. In electrochemistry, a valve metal is a metal which passes current in only one direction due to the formation of any insulating oxide later. There are many ceramic compounds which have metallic electrical conduction, but are not simple combinations of metallic elements. (They are not

1065-677: A star that are heavier than helium . In this sense the first four "metals" collecting in stellar cores through nucleosynthesis are carbon , nitrogen , oxygen , and neon . A star fuses lighter atoms, mostly hydrogen and helium, into heavier atoms over its lifetime. The metallicity of an astronomical object is the proportion of its matter made up of the heavier chemical elements. The strength and resilience of some metals has led to their frequent use in, for example, high-rise building and bridge construction , as well as most vehicles, many home appliances , tools, pipes, and railroad tracks. Precious metals were historically used as coinage , but in

1136-400: A star until they form cadmium-115 nuclei which are unstable and decay to form indium-115 (which is nearly stable, with a half-life 30 000 times the age of the universe). These nuclei capture neutrons and form indium-116, which is unstable, and decays to form tin-116, and so on. In contrast, there is no such path in the r-process. The s-process stops at bismuth due to the short half-lives of

1207-471: A temperature of absolute zero , which is a consequence of delocalized states at the Fermi energy. Many elements and compounds become metallic under high pressures, for example, iodine gradually becomes a metal at a pressure of between 40 and 170 thousand times atmospheric pressure . Sodium becomes a nonmetal at pressure of just under two million times atmospheric pressure, and at even higher pressures it

1278-403: Is a metal that is very resistant to heat and wear. Which metals belong to this category varies; the most common definition includes niobium, molybdenum, tantalum, tungsten, and rhenium as well as their alloys. They all have melting points above 2000 °C, and a high hardness at room temperature. Several compounds such as titanium nitride are also described as refractory metals. A white metal

1349-611: Is any of a range of white-colored alloys with relatively low melting points used mainly for decorative purposes. In Britain, the fine art trade uses the term "white metal" in auction catalogues to describe foreign silver items which do not carry British Assay Office marks, but which are nonetheless understood to be silver and are priced accordingly. A heavy metal is any relatively dense metal, either single element or multielement. Magnesium , aluminium and titanium alloys are light metals of significant commercial importance. Their densities of 1.7, 2.7 and 4.5 g/cm range from 19 to 56% of

1420-484: Is composed mostly of iron, is thought to be the source of Earth's protective magnetic field. The core lies above Earth's solid inner core and below its mantle. If it could be rearranged into a column having a 5 m (54 sq ft) footprint it would have a height of nearly 700 light years. The magnetic field shields the Earth from the charged particles of the solar wind, and cosmic rays that would otherwise strip away

1491-572: Is evidence that this and comparable behavior in transuranic elements is due to more complex relativistic and spin interactions which are not captured in simple models. All of the metallic alloys as well as conducting ceramics and polymers are metals by the same definition; for instance titanium nitride has delocalized states at the Fermi level. They have electrical conductivities similar to those of elemental metals. Liquid forms are also metallic conductors or electricity, for instance mercury . In normal conditions no gases are metallic conductors. However,

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1562-422: Is expected to become a metal again. When discussing the periodic table and some chemical properties the term metal is often used to denote those elements which in pure form and at standard conditions are metals in the sense of electrical conduction mentioned above. The related term metallic may also be used for types of dopant atoms or alloying elements. In astronomy metal refers to all chemical elements in

1633-522: Is intended for remelting, the uneven size of the ingots and the inclusion of small amounts of sand are insignificant issues when compared to the ease of casting and handling. The Chinese were already making pig iron during the later Zhou dynasty (which ended in 256 BC). Furnaces such as Lapphyttan in Sweden may date back as far back as the 12th century; and some in the County of Mark dating back to

1704-548: Is no external voltage . When a voltage is applied some move a little faster in a given direction, some a little slower so there is a net drift velocity which leads to an electric current. This involves small changes in which wavefunctions the electrons are in, changing to those with the higher momenta. Quantum mechanics dictates that one can only have one electron in a given state, the Pauli exclusion principle . Therefore there have to be empty delocalized electron states (with

1775-474: Is not. In the context of metals, an alloy is a substance having metallic properties which is composed of two or more elements . Often at least one of these is a metallic element; the term "alloy" is sometimes used more generally as in silicon–germanium alloys. An alloy may have a variable or fixed composition. For example, gold and silver form an alloy in which the proportions of gold or silver can be varied; titanium and silicon form an alloy TiSi 2 in which

1846-575: Is positioned at the center of a cube of eight others. In fcc and hcp, each atom is surrounded by twelve others, but the stacking of the layers differs. Some metals adopt different structures depending on the temperature. Many other metals with different elements have more complicated structures, such as rock-salt structure in titanium nitride or perovskite (structure) in some nickelates. The electronic structure of metals means they are relatively good conductors of electricity . The electrons all have different momenta , which average to zero when there

1917-656: Is via single crystal dendrite and not via simple casting. Possible uses include turbine blades . In the United States, the brass and bronze ingot making industry started in the early 19th century. The US brass industry grew to be the number one producer by the 1850s. During colonial times the brass and bronze industries were almost non-existent because the British demanded all copper ore be sent to Britain for processing. Copper based alloy ingots weighed approximately 20 pounds (9.1 kg). Ingots are manufactured by

1988-455: The Bessemer process , and the open hearth furnace . Modern steel mills and direct-reduction iron plants transfer the molten iron to a ladle for immediate use in the steel making furnaces or cast it into pigs on a pig-casting machine for reuse or resale. Modern pig casting machines produce stick pigs, which break into smaller 4–10 kg piglets at discharge. Ingot An ingot is

2059-474: The Burgers vector of the dislocations are fairly small, which also means that the energy needed to produce one is small. In contrast, in an ionic compound like table salt the Burgers vectors are much larger and the energy to move a dislocation is far higher. Reversible elastic deformation in metals can be described well by Hooke's Law for the restoring forces, where the stress is linearly proportional to

2130-415: The periodic table . If there are several, the most stable allotrope is considered. The situation changes with pressure: at extremely high pressures, all elements (and indeed all substances) are expected to metallize. Arsenic (As) has both a stable metallic allotrope and a metastable semiconducting allotrope at standard conditions. A similar situation affects carbon (C): graphite is metallic, but diamond

2201-419: The steel mill in mostly liquid form; in this state, the pig iron was referred to as hot metal . The hot metal was then poured into a steelmaking vessel to produce steel , typically an electric arc furnace , induction furnace or basic oxygen furnace , where the excess carbon is burned off and the alloy composition controlled. Earlier processes for this included the finery forge , the puddling furnace ,

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2272-539: The strain . A temperature change may lead to the movement of structural defects in the metal such as grain boundaries , point vacancies , line and screw dislocations , stacking faults and twins in both crystalline and non-crystalline metals. Internal slip , creep , and metal fatigue may also ensue. The atoms of simple metallic substances are often in one of three common crystal structures , namely body-centered cubic (bcc), face-centered cubic (fcc), and hexagonal close-packed (hcp). In bcc, each atom

2343-486: The vicinity of iron (in the periodic table) are largely made via stellar nucleosynthesis . In this process, lighter elements from hydrogen to silicon undergo successive fusion reactions inside stars, releasing light and heat and forming heavier elements with higher atomic numbers. Heavier elements are not usually formed this way since fusion reactions involving such nuclei would consume rather than release energy. Rather, they are largely synthesised (from elements with

2414-608: The 13th century, which is now part of Westphalia , Germany. It remains to be established whether these northern European developments were derived from the Chinese ones. Wagner has postulated a possible link via Persian contacts with China along the Silk Road and Viking contacts with Persia, but there is a chronological gap between the Viking period and Lapphyttan. Smelting and producing wrought iron were known in ancient Europe and

2485-484: The Middle East, but it was produced in bloomeries by direct reduction . Small prills of pig iron dispersed in slag are produced in all iron furnaces, but the operator of a bloomery had to avoid conditions causing the phase transition of the iron into liquid in the furnace, as the prill globules or any resulting pig iron are not malleable so can't be hammered in a single piece. Alternatively, decarburizing

2556-483: The addition of chromium , nickel , and molybdenum to carbon steels (more than 10%) results in stainless steels with enhanced corrosion resistance. Other significant metallic alloys are those of aluminum , titanium , copper , and magnesium . Copper alloys have been known since prehistory— bronze gave the Bronze Age its name—and have many applications today, most importantly in electrical wiring. The alloys of

2627-599: The air to form oxides over various timescales ( potassium burns in seconds while iron rusts over years) which depend upon whether the native oxide forms a passivation layer that acts as a diffusion barrier . Some others, like palladium , platinum , and gold , do not react with the atmosphere at all; gold can form compounds where it gains an electron (aurides, e.g. caesium auride ). The oxides of elemental metals are often basic . However, oxides with very high oxidation states such as CrO 3 , Mn 2 O 7 , and OsO 4 often have strictly acidic reactions; and oxides of

2698-426: The cast ingot useless and may need to be re-melted, recycled, or discarded. The physical structure of a crystalline material is largely determined by the method of cooling and precipitation of the molten metal. During the pouring process, metal in contact with the ingot walls rapidly cools and forms either a columnar structure or possibly a "chill zone" of equiaxed dendrites , depending upon the liquid being cooled and

2769-461: The cooling of a molten liquid (known as the melt) in a mold. The manufacture of ingots has several aims. Firstly, the mold is designed to completely solidify and form an appropriate grain structure required for later processing, as the structure formed by the cooling of the melt controls the physical properties of the material. Secondly, the shape and size of the mold is designed to allow for ease of ingot handling and downstream processing. Finally,

2840-429: The cooling rate of the mold. For a top-poured ingot, as the liquid cools within the mold, differential volume effects cause the top of the liquid to recede leaving a curved surface at the mold top which may eventually be required to be machined from the ingot. The mold cooling effect creates an advancing solidification front, which has several associated zones, closer to the wall there is a solid zone that draws heat from

2911-406: The densities of other structural metals, such as iron (7.9) and copper (8.9) and their alloys. The term base metal refers to a metal that is easily oxidized or corroded , such as reacting easily with dilute hydrochloric acid (HCl) to form a metal chloride and hydrogen . The term is normally used for the elements, and examples include iron, nickel , lead , and zinc. Copper is considered

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2982-495: The detailed structure of the metal's ion lattice. Taking into account the positive potential caused by the arrangement of the ion cores enables consideration of the electronic band structure and binding energy of a metal. Various models are applicable, the simplest being the nearly free electron model . Modern methods such as density functional theory are typically used. The elements which form metals usually form cations through electron loss. Most will react with oxygen in

3053-510: The dissolved impurities (such as silicon) to be thoroughly oxidized. An intermediate product of puddling is known as refined pig iron , finers metal , or refined iron . Pig iron can also be used to produce gray iron . This is achieved by remelting pig iron, often along with substantial quantities of steel and scrap iron, removing undesirable contaminants, adding alloys, and adjusting the carbon content. Ductile iron can also be produced using certain high purity grades of pig iron; depending on

3124-456: The elements from fermium (Fm) onwards are shown in gray because they are extremely radioactive and have never been produced in bulk. Theoretical and experimental evidence suggests that these uninvestigated elements should be metals, except for oganesson (Og) which DFT calculations indicate would be a semiconductor. Metallic Network covalent Molecular covalent Single atoms Unknown Background color shows bonding of simple substances in

3195-433: The f-block elements. They have a strong affinity for oxygen and mostly exist as relatively low-density silicate minerals. Chalcophile elements are mainly the less reactive d-block elements, and the period 4–6 p-block metals. They are usually found in (insoluble) sulfide minerals. Being denser than the lithophiles, hence sinking lower into the crust at the time of its solidification, the chalcophiles tend to be less abundant than

3266-420: The first known appearance of bronze in the fifth millennium BCE. Subsequent developments include the production of early forms of steel; the discovery of sodium —the first light metal —in 1809; the rise of modern alloy steels ; and, since the end of World War II, the development of more sophisticated alloys. Most metals are shiny and lustrous , at least when polished, or fractured. Sheets of metal thicker than

3337-414: The grade of ductile iron being produced, the pig irons chosen may be low in the elements silicon, manganese, sulfur and phosphorus. High purity pig iron is used to dilute any elements in a ductile iron charge which may be harmful to the ductile iron process (except carbon). Pig iron was historically poured directly out of the bottom of the blast furnace through a trough into a ladle car for transfer to

3408-724: The higher momenta) available at the highest occupied energies as sketched in the Figure. In a semiconductor like silicon or a nonmetal like strontium titanate there is an energy gap between the highest filled states of the electrons and the lowest unfilled, so no accessible states with slightly higher momenta. Consequently, semiconductors and nonmetals are poor conductors, although they can carry some current when doped with elements that introduce additional partially occupied energy states at higher temperatures. The elemental metals have electrical conductivity values of from 6.9 × 10 S /cm for manganese to 6.3 × 10 S/cm for silver . In contrast,

3479-607: The history of metallurgy . Metal A metal (from Ancient Greek μέταλλον ( métallon )  'mine, quarry, metal') is a material that, when polished or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. These properties are all associated with having electrons available at the Fermi level , as against nonmetallic materials which do not. Metals are typically ductile (can be drawn into wires) and malleable (they can be hammered into thin sheets). A metal may be

3550-436: The known examples of half-metals are oxides , sulfides , or Heusler alloys . A semimetal is a material with a small energy overlap between the bottom of the conduction band and the top of the valence band , but they do not overlap in momentum space . Unlike a regular metal, semimetals have charge carriers of both types (holes and electrons), although the charge carriers typically occur in much smaller numbers than in

3621-482: The less electropositive metals such as BeO, Al 2 O 3 , and PbO, can display both basic and acidic properties. The latter are termed amphoteric oxides. The elements that form exclusively metallic structures under ordinary conditions are shown in yellow on the periodic table below. The remaining elements either form covalent network structures (light blue), molecular covalent structures (dark blue), or remain as single atoms (violet). Astatine (At), francium (Fr), and

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3692-621: The liquid melt alloy compositions. Continuous casting methods for ingot processing also exist, whereby a stationary front of solidification is formed by the continual take-off of cooled solid material, and the addition of a molten liquid to the casting process. Approximately 70 percent of aluminium ingots in the U.S. are cast using the direct chill casting process, which reduces cracking. A total of 5 percent of ingots must be scrapped because of stress induced cracks and butt deformation. Plano-convex ingots are widely distributed archaeological artifacts which are studied to provide information on

3763-408: The lithophiles. On the other hand, gold is a siderophile, or iron-loving element. It does not readily form compounds with either oxygen or sulfur. At the time of the Earth's formation, and as the most noble (inert) of metallic elements, gold sank into the core due to its tendency to form high-density metallic alloys. Consequently, it is relatively rare. Some other (less) noble ones—molybdenum, rhenium,

3834-407: The metallic alloys in use today, the alloys of iron ( steel , stainless steel , cast iron , tool steel , alloy steel ) make up the largest proportion both by quantity and commercial value. Iron alloyed with various proportions of carbon gives low-, mid-, and high-carbon steels, with increasing carbon levels reducing ductility and toughness. The addition of silicon will produce cast irons, while

3905-412: The modern era, coinage metals have extended to at least 23 of the chemical elements. There is also extensive use of multi-element metals such as titanium nitride or degenerate semiconductors in the semiconductor industry. The history of refined metals is thought to begin with the use of copper about 11,000 years ago. Gold, silver, iron (as meteoric iron), lead, and brass were likewise in use before

3976-452: The mold is designed to minimize melt wastage and aid ejection of the ingot, as losing either melt or ingot increases manufacturing costs of finished products. A variety of designs exist for the mold, which may be selected to suit the physical properties of the liquid melt and the solidification process. Molds may exist in the top, horizontal or bottom-up pouring and may be fluted or flat walled. The fluted design increases heat transfer owing to

4047-401: The next two elements, polonium and astatine, which decay to bismuth or lead. The r-process is so fast it can skip this zone of instability and go on to create heavier elements such as thorium and uranium. Metals condense in planets as a result of stellar evolution and destruction processes. Stars lose much of their mass when it is ejected late in their lifetimes, and sometimes thereafter as

4118-493: The nitrogen. However, unlike most elemental metals, ceramic metals are often not particularly ductile. Their uses are widespread, for instance titanium nitride finds use in orthopedic devices and as a wear resistant coating. In many cases their utility depends upon there being effective deposition methods so they can be used as thin film coatings. There are many polymers which have metallic electrical conduction, typically associated with extended aromatic components such as in

4189-623: The older structural metals, like iron at 7.9 and copper at 8.9 g/cm . The most common lightweight metals are aluminium and magnesium alloys. Metals are typically malleable and ductile, deforming under stress without cleaving . The nondirectional nature of metallic bonding contributes to the ductility of most metallic solids, where the Peierls stress is relatively low allowing for dislocation motion, and there are also many combinations of planes and directions for plastic deformation . Due to their having close packed arrangements of atoms

4260-702: The other three metals have been developed relatively recently; due to their chemical reactivity they need electrolytic extraction processes. The alloys of aluminum, titanium, and magnesium are valued for their high strength-to-weight ratios; magnesium can also provide electromagnetic shielding . These materials are ideal for situations where high strength-to-weight ratio is more important than material cost, such as in aerospace and some automotive applications. Alloys specially designed for highly demanding applications, such as jet engines , may contain more than ten elements. Metals can be categorised by their composition, physical or chemical properties. Categories described in

4331-400: The overall scarcity of some heavier metals such as copper, they can become concentrated in economically extractable quantities as a result of mountain building, erosion, or other geological processes. Metallic elements are primarily found as lithophiles (rock-loving) or chalcophiles (ore-loving). Lithophile elements are mainly the s-block elements, the more reactive of the d-block elements, and

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4402-543: The pig iron into steel was an extremely tedious process using medieval technology, so in Europe before the Middle Ages the prills were discarded with the slag. Traditionally, pig iron was worked into wrought iron in finery forges , later puddling furnaces , and more recently, into steel . In these processes, pig iron is melted and a strong current of air is directed over it while it is stirred or agitated. This causes

4473-420: The platinum group metals (ruthenium, rhodium, palladium, osmium, iridium, and platinum), germanium, and tin—can be counted as siderophiles but only in terms of their primary occurrence in the Earth (core, mantle, and crust), rather the crust. These otherwise occur in the crust, in small quantities, chiefly as chalcophiles (less so in their native form). The rotating fluid outer core of the Earth's interior, which

4544-547: The polymers indicated in the Figure. The conduction of the aromatic regions is similar to that of graphite, so is highly directional. A half-metal is any substance that acts as a conductor to electrons of one spin orientation, but as an insulator or semiconductor to those of the opposite spin. They were first described in 1983, as an explanation for the electrical properties of manganese -based Heusler alloys . Although all half-metals are ferromagnetic (or ferrimagnetic ), most ferromagnets are not half-metals. Many of

4615-408: The ratio between thermal and electrical conductivities is proportional to temperature, with a proportionality constant that is roughly the same for all metals. The contribution of a metal's electrons to its heat capacity and thermal conductivity, and the electrical conductivity of the metal itself can be approximately calculated from the free electron model . However, this does not take into account

4686-415: The ratio of the two components is fixed (also known as an intermetallic compound ). Most pure metals are either too soft, brittle, or chemically reactive for practical use. Combining different ratios of metals and other elements in alloys modifies the properties to produce desirable characteristics, for instance more ductile, harder, resistant to corrosion, or have a more desirable color and luster. Of all

4757-416: The same as cermets which are composites of a non-conducting ceramic and a conducting metal.) One set, the transition metal nitrides has significant ionic character to the bonding, so can be classified as both ceramics and metals. They have partially filled states at the Fermi level so are good thermal and electrical conductors, and there is often significant charge transfer from the transition metal atoms to

4828-411: The solidifying melt, for alloys there may exist a "mushy" zone, which is the result of solid-liquid equilibrium regions in the alloy's phase diagram , and a liquid region. The rate of front advancement controls the time that dendrites or nuclei have to form in the solidification region. The width of the mushy zone in an alloy may be controlled by tuning the heat transfer properties of the mold or adjusting

4899-635: The subsections below include ferrous and non-ferrous metals; brittle metals and refractory metals ; white metals; heavy and light metals; base , noble , and precious metals as well as both metallic ceramics and polymers . The term "ferrous" is derived from the Latin word meaning "containing iron". This can include pure iron, such as wrought iron , or an alloy such as steel . Ferrous metals are often magnetic , but not exclusively. Non-ferrous metals and alloys lack appreciable amounts of iron. While nearly all elemental metals are malleable or ductile,

4970-474: The term base metal is contrasted with precious metal , that is, those of high economic value. Most coins today are made of base metals with low intrinsic value ; in the past, coins frequently derived their value primarily from their precious metal content; gold , silver , platinum , and palladium each have an ISO 4217 currency code. Currently they have industrial uses such as platinum and palladium in catalytic converters , are used in jewellery and also

5041-496: The upper atmosphere (including the ozone layer that limits the transmission of ultraviolet radiation). Metallic elements are often extracted from the Earth by mining ores that are rich sources of the requisite elements, such as bauxite . Ores are located by prospecting techniques, followed by the exploration and examination of deposits. Mineral sources are generally divided into surface mines , which are mined by excavation using heavy equipment, and subsurface mines . In some cases,

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