1.
Recycling
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Recycling is the process of converting waste materials into new materials and objects. It is an alternative to conventional waste disposal that can save material, Recycling can prevent the waste of potentially useful materials and reduce the consumption of fresh raw materials, thereby reducing, energy usage, air pollution, and water pollution. Recycling is a key component of waste reduction and is the third component of the Reduce, Reuse. There are some ISO standards related to recycling such as ISO15270,2008 for plastics waste, recyclable materials include many kinds of glass, paper, and cardboard, metal, plastic, tires, textiles, and electronics. The composting or other reuse of biodegradable waste—such as food or garden waste—is also considered recycling, materials to be recycled are either brought to a collection centre or picked up from the curbside, then sorted, cleaned, and reprocessed into new materials destined for manufacturing. However, this is difficult or too expensive, so recycling of many products or materials involves their reuse in producing different materials instead. Another form of recycling is the salvage of materials from complex products, either due to their intrinsic value. Recycling has been a practice for most of human history. In pre-industrial times, there is evidence of bronze and other metals being collected in Europe. Paper recycling was first recorded in 1031 when Japanese shops sold repulped paper, in Britain dust and ash from wood and coal fires was collected by dustmen and downcycled as a base material used in brick making. In 1813, Benjamin Law developed the process of turning rags into shoddy and mungo wool in Batley and this material combined recycled fibers with virgin wool. The West Yorkshire shoddy industry in such as Batley and Dewsbury lasted from the early 19th century to at least 1914. Industrialization spurred demand for materials, aside from rags, ferrous scrap metals were coveted as they were cheaper to acquire than virgin ore. Railroads both purchased and sold scrap metal in the 19th century, and the steel and automobile industries purchased scrap in the early 20th century. Many secondary goods were collected, processed and sold by peddlers who scoured dumps and city streets for discarded machinery, pots, pans, and other sources of metal. By World War I, thousands of such peddlers roamed the streets of American cities, beverage bottles were recycled with a refundable deposit at some drink manufacturers in Great Britain and Ireland around 1800, notably Schweppes. New chemical industries created in the late 19th century both invented new materials (e. g. Bakelite and promised to transform valueless into valuable materials, new and better paths are opened to reach the goals desired. Recycling was a highlight throughout World War II, during the war, financial constraints and significant material shortages due to war efforts made it necessary for countries to reuse goods and recycle materials
2.
Waste
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Waste and wastes are unwanted or unusable materials. Waste is any substance which is discarded after use, or it is worthless, defective. Examples include municipal solid waste, hazardous waste, wastewater, radioactive waste, according to the Basel Convention on the Control of Transboundary Movements of Hazardous Wastes and Their Disposal of 1989, Art. 2, Wastes are substance or objects, which are disposed of or are intended to be disposed of or are required to be disposed of by the provisions of national law. Wastes may be generated during the extraction of raw materials, the processing of raw materials into intermediate and final products, the consumption of final products, residuals recycled or reused at the place of generation are excluded. Under the Waste Framework Directive 2008/98/EC, Art,3, the European Union defines waste as an object the holder discards, intends to discard or is required to discard. For a more structural description of the Waste Directive, see the European Commissions summary and it is most commonly measured by size or weight, and there is a stark difference between the two. For example, organic waste is much heavier when it is wet, on a global scale it is difficult to report waste because countries have different definitions of waste and what falls into waste categories, as well as different ways of reporting. Based on incomplete reports from its parties, the Basel Convention estimated 338 million tonnes of waste was generated in 2001, for the same year, OECD estimated 4 billion tonnes from its member countries. Toxic waste materials can contaminate surface water, groundwater, soil, and air which causes problems for humans, other species. Waste treatment and disposal produces significant green house gas emissions, notably methane, Waste management is a significant environmental justice issue. Many of the environmental burdens cited above are often borne by marginalized groups, such as racial minorities, women. NIMBY is the opposition of residents to a proposal for a new development because it is close to them, however, the need for expansion and siting of waste treatment and disposal facilities is increasing worldwide. Environmental policies such as pay as you throw can reduce the cost of management, Waste recovery can curb economic costs because it avoids extracting raw materials and often cuts transportation costs. Economic assessment of municipal waste management systems – case studies using a combination of life-cycle assessment, the location of waste treatment and disposal facilities often reduces property values due to noise, dust, pollution, unsightliness, and negative stigma. The informal waste sector consists mostly of waste pickers who scavenge for metals, glass, plastic, textiles, and other materials and then trade them for a profit. This sector can significantly alter or reduce waste in a system, but other negative economic effects come with the disease, poverty, exploitation. Resource recovery is the retrieval of recyclable waste, which was intended for disposal and it is the processing of recyclables to extract or recover materials and resources, or convert to energy
3.
Metal
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A metal is a material that is typically hard, opaque, shiny, and has good electrical and thermal conductivity. Metals are generally malleable—that is, they can be hammered or pressed permanently out of shape without breaking or cracking—as well as fusible and ductile, about 91 of the 118 elements in the periodic table are metals, the others are nonmetals or metalloids. Some elements appear in both metallic and non-metallic forms, astrophysicists use the term metal to collectively describe all elements other than hydrogen and helium, the simplest two, in a star. The star fuses smaller atoms, mostly hydrogen and helium, to larger ones over its lifetime. In that sense, the metallicity of an object is the proportion of its matter made up of all chemical elements. Many elements and compounds that are not normally classified as metals become metallic under high pressures, the atoms of metallic substances are typically arranged in one of three common crystal structures, namely body-centered cubic, face-centered cubic, and hexagonal close-packed. In bcc, each atom 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, atoms of metals readily lose their outer shell electrons, resulting in a free flowing cloud of electrons within their otherwise solid arrangement. This provides the ability of metallic substances to easily transmit heat, while this flow of electrons occurs, the solid characteristic of the metal is produced by electrostatic interactions between each atom and the electron cloud. This type of bond is called a metallic bond, Metals are usually inclined to form cations through electron loss, reacting with oxygen in the air to form oxides over various timescales. Examples,4 Na + O2 →2 Na2O2 Ca + O2 →2 CaO4 Al +3 O2 →2 Al2O3, the transition metals are slower to oxidize because they form a passivating layer of oxide that protects the interior. Others, like palladium, platinum and gold, do not react with the atmosphere at all, some metals form a barrier layer of oxide on their surface which cannot be penetrated by further oxygen molecules and thus retain their shiny appearance and good conductivity for many decades. The oxides of metals are generally basic, as opposed to those of nonmetals, exceptions are largely oxides with very high oxidation states such as CrO3, Mn2O7, and OsO4, which have strictly acidic reactions. Painting, anodizing or plating metals are good ways to prevent their corrosion, however, a more reactive metal in the electrochemical series must be chosen for coating, especially when chipping of the coating is expected. Water and the two form an electrochemical cell, and if the coating is less reactive than the coatee. Metals in general have high conductivity, high thermal conductivity. Typically they are malleable and ductile, deforming under stress without cleaving, in terms of optical properties, metals are shiny and lustrous. Sheets of metal beyond a few micrometres in thickness appear opaque, although most metals have higher densities than most nonmetals, there is wide variation in their densities, lithium being the least dense solid element and osmium the densest
4.
Wrecking yard
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Other terms include wreck yard, wreckers yard, salvage yard, breakers yard, dismantler and scrapheap. In the United Kingdom, car salvage yards are known as car breakers, in Australia, they are often referred to as Wreckers. The most common type of wreck yards are automobile wreck yards, a scrapyard is a recycling center that buys and sells scrap metal. Scrapyards are effectively a scrap metal brokerage, scrap yards typically buy any base metal, for example, iron, steel, stainless steel, brass, copper, aluminum, zinc, nickel, and lead would all be found at a modern-day scrapyard. Scrapyards will often buy electronics, appliances, and metal vehicles, scrapyards will sell their accumulations of metals either to refineries or larger scrap brokers. Metal theft is committed so thieves can sell stolen copper or other valuable metals to scrapyards. Salvage yards also buy most of the wrecked, derelict and abandoned vehicles that are sold at auction from police impound storage lots, the salvage yard will usually tow the vehicle from the location of its purchase to the yard, but occasionally vehicles are driven in. At the salvage yard the automobiles are typically arranged in rows, some yards keep inventories in their offices, as to the usable parts in each car, as well as the cars location in the yard. Many yards have computerized inventory systems, about 75% of any given vehicle can be recycled and used for other goods. In recent years it is becoming common to use satellite part finder services to contact multiple salvage yards from a single source. Many of these are now Web-based with requests for parts being e-mailed instantly, often parts for which there is high demand are removed from cars and brought to the salvage yards warehouse. Then a customer who asks for a part can get it immediately. Some salvage yards expect customers to remove the part themselves, or allow this at a reduced price compared to having the junkyards staff remove it. This style of yard is often referred to as a You Pull It yard, however, it is more common for a customer to call in and inquire whether the specific item he/she needs is available. If the yard has the item, the customer is usually asked to leave a deposit. The part is typically installed by the customer or agent, however, the parts typically dismantled from automobiles are generally any that can be re-sold such as the light assemblies, seats, parts of the exhaust system, mirrors, hubcaps etc. Late model vehicles will often have entire halves or sections of the body removed and stored on shelves as inventory, other, usually very large, junkyards will rebuild and sell such parts themselves. Unbroken windshields and windows may also be removed intact and resold to car-owners needing replacements and these cars are known as rebuilders
5.
Machine (mechanical)
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Machines employ power to achieve desired forces and movement. A machine has a source and actuators that generate forces and movement. Modern machines often include computers and sensors that monitor performance and plan movement, the meaning of the word machine is traced by the Oxford English Dictionary to an independently functioning structure and by Merriam-Webster Dictionary to something that has been constructed. This includes human design into the meaning of machine, similarly Merriam-Webster Dictionary defines mechanical as relating to machinery or tools. Power flow through a machine provides a way to understand the performance of devices ranging from levers and gear trains to automobiles, notice that forces and motion combine to define power. More recently, Uicker et al. stated that a machine is a device for applying power or changing its direction, and McCarthy and Soh describe a machine as a system that generally consists of a power source and a mechanism for the controlled use of this power. The idea that a machine can be decomposed into simple movable elements led Archimedes to define the lever, pulley, by the time of the Renaissance this list increased to include the wheel and axle, wedge and inclined plane. The modern approach to characterizing machines focusses on the components that allow movement, wedge, Perhaps the first example of a device designed to manage power is the hand axe, also see biface and Olorgesailie. A hand axe is made by chipping stone, generally flint, to form a bifacial edge, a wedge is a simple machine that transforms lateral force and movement of the tool into a transverse splitting force and movement of the workpiece. The available power is limited by the effort of the using the tool, but because power is the product of force and movement. This amplification, or mechanical advantage is the ratio of the speed to output speed. For a wedge this is given by 1/tanα, where α is the tip angle, the faces of a wedge are modeled as straight lines to form a sliding or prismatic joint. Lever, The lever is another important and simple device for managing power and this is a body that pivots on a fulcrum. The fulcrum of a lever is modeled as a hinged or revolute joint, wheel, The wheel is clearly an important early machine, such as the chariot. A wheel uses the law of the lever to reduce the force needed to overcome friction when pulling a load. To see this notice that the associated with pulling a load on the ground is approximately the same as the friction in a simple bearing that supports the load on the axle of a wheel. However, the forms a lever that magnifies the pulling force so that it overcomes the frictional resistance in the bearing. Natural forces such as wind and water powered larger mechanical systems, waterwheels appeared around the world around 300 BC to use flowing water to generate rotary motion, which was applied to milling grain, and powering lumber, machining and textile operations
6.
Stainless steel
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In metallurgy, stainless steel, also known as inox steel or inox from French inoxydable, is a steel alloy with a minimum of 10. 5% chromium content by mass. Stainless steel is notable for its resistance, and it is widely used for food handling. Stainless steel does not readily corrode, rust or stain with water as ordinary steel does, however, it is not fully stain-proof in low-oxygen, high-salinity, or poor air-circulation environments. There are various grades and surface finishes of stainless steel to suit the environment the alloy must endure, Stainless steel is used where both the properties of steel and corrosion resistance are required. Stainless steel differs from carbon steel by the amount of chromium present, unprotected carbon steel rusts readily when exposed to air and moisture. This iron oxide film is active and accelerates corrosion by making it easier for more iron oxide to form, since iron oxide has lower density than steel, the film expands and tends to flake and fall away. In comparison, stainless steels contain sufficient chromium to undergo passivation and this layer prevents further corrosion by blocking oxygen diffusion to the steel surface and stops corrosion from spreading into the bulk of the metal. Passivation occurs only if the proportion of chromium is high enough, Stainless steel’s resistance to corrosion and staining, low maintenance, and familiar lustre make it an ideal material for many applications. Storage tanks and tankers used to transport orange juice and other food are made of stainless steel. This also influences its use in kitchens and food processing plants, as it can be steam-cleaned and sterilized. High oxidation resistance in air at ambient temperature is achieved with addition of a minimum of 13% chromium. The chromium forms a layer of chromium oxide when exposed to oxygen. The layer is too thin to be visible, and the metal remains lustrous, the layer is impervious to water and air, protecting the metal beneath, and this layer quickly reforms when the surface is scratched. This phenomenon is called passivation and is seen in other metals, corrosion resistance can be adversely affected if the component is used in a non-oxygenated environment, a typical example being underwater keel bolts buried in timber. When stainless steel parts such as nuts and bolts are forced together, when forcibly disassembled, the welded material may be torn and pitted, a destructive effect known as galling. Galling can be avoided by the use of materials for the parts forced together, for example bronze and stainless steel. However, two different alloys electrically connected in a humid, even mildly acidic environment may act as a voltaic pile, nitronic alloys, made by selective alloying with manganese and nitrogen, may have a reduced tendency to gall. Additionally, threaded joints may be lubricated to provide a film between the two parts and prevent galling, low-temperature carburizing is another option that virtually eliminates galling and allows the use of similar materials without the risk of corrosion and the need for lubrication
7.
Asbestos
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They are commonly known by their colors, as blue asbestos, brown asbestos, white asbestos, and green asbestos. It was used in applications as electrical insulation for hotplate wiring. When asbestos is used for its resistance to fire or heat and these desirable properties made asbestos very widely used. Prolonged inhalation of asbestos fibers can cause serious and fatal illnesses including cancer, mesothelioma. Concern of asbestos-related illness in modern times began in the 20th century, by the 1980s and 1990s, asbestos trade and use were heavily restricted, phased out, or banned outright in an increasing number of countries. S. History and a much lesser legal issue in most other countries involved, asbestos-related liability also remains an ongoing concern for many manufacturers, insurers and reinsurers. Asbestos derives from the ancient Greek ἄσβεστος, meaning unquenchable or inextinguishable, the word is pronounced /æsˈbɛstəs/, /æzˈbɛstəs/ or /æzˈbɛstɒs/. Six mineral types are defined by the United States Environmental Protection Agency as asbestos including those belonging to the serpentine class, all six asbestos mineral types are known to be human carcinogens. The visible fibers are themselves composed of millions of microscopic fibrils that can be released by abrasion. Chrysotile is the member of the serpentine class. 12001-29-5, is obtained from rocks which are common throughout the world. Its idealized chemical formula is Mg34, chrysotile appears under the microscope as a white fiber. Chrysotile has been used more than any type and accounts for about 95% of the asbestos found in buildings in America. Chrysotile is more flexible than amphibole types of asbestos, and can be spun, the most common use was corrugated asbestos cement roofing primarily for outbuildings, warehouses and garages. It may also be found in sheets or panels used for ceilings and sometimes for walls, chrysotile has been a component in joint compound and some plasters. Amosite, crocidolite, tremolite, anthophyllite and actinolite are members of the amphibole class, one formula given for amosite is Fe7Si8O222. Amosite is seen under a microscope as a grey-white vitreous fiber and it is found most frequently as a fire retardant in thermal insulation products, asbestos insulating board and ceiling tiles. 12001-28-4, is the form of the amphibole riebeckite, found primarily in southern Africa
8.
Mercury (element)
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Mercury is a chemical element with symbol Hg and atomic number 80. It is commonly known as quicksilver and was formerly named hydrargyrum, Mercury occurs in deposits throughout the world mostly as cinnabar. The red pigment vermilion is obtained by grinding natural cinnabar or synthetic mercuric sulfide, likewise, mechanical pressure gauges and electronic strain gauge sensors have replaced mercury sphygmomanometers. Mercury remains in use in research applications and in amalgam for dental restoration in some locales. It is used in fluorescent lighting, electricity passed through mercury vapor in a fluorescent lamp produces short-wave ultraviolet light which then causes the phosphor in the tube to fluoresce, making visible light. Mercury poisoning can result from exposure to water-soluble forms of mercury, Mercury is a heavy, silvery-white liquid metal. Compared to other metals, it is a conductor of heat. It has a point of −38.83 °C and a boiling point of 356.73 °C. Upon freezing, the volume of mercury decreases by 3. 59%, the coefficient of volume expansion is 181.59 × 10−6 at 0 °C,181.71 × 10−6 at 20 °C and 182.50 × 10−6 at 100 °C. Solid mercury is malleable and ductile and can be cut with a knife, because this configuration strongly resists removal of an electron, mercury behaves similarly to noble gases, which form weak bonds and hence melt at low temperatures. The stability of the 6s shell is due to the presence of a filled 4f shell, an f shell poorly screens the nuclear charge that increases the attractive Coulomb interaction of the 6s shell and the nucleus. Like silver, mercury reacts with hydrogen sulfide. Mercury reacts with solid sulfur flakes, which are used in mercury spill kits to absorb mercury, Mercury dissolves many other metals such as gold and silver to form amalgams. Iron is an exception, and iron flasks have traditionally used to trade mercury. Several other first row transition metals with the exception of manganese, copper, other elements that do not readily form amalgams with mercury include platinum. Sodium amalgam is a reducing agent in organic synthesis, and is also used in high-pressure sodium lamps. Mercury readily combines with aluminium to form a mercury-aluminium amalgam when the two pure metals come into contact, since the amalgam destroys the aluminium oxide layer which protects metallic aluminium from oxidizing in-depth, even small amounts of mercury can seriously corrode aluminium. For this reason, mercury is not allowed aboard an aircraft under most circumstances because of the risk of it forming an amalgam with exposed aluminium parts in the aircraft, Mercury embrittlement is the most common type of liquid metal embrittlement
9.
United States Environmental Protection Agency
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The EPA was proposed by President Richard Nixon and began operation on December 2,1970, after Nixon signed an executive order. The order establishing the EPA was ratified by committee hearings in the House, the agency is led by its Administrator, who is appointed by the president and approved by Congress. The current administrator is Scott Pruitt, the EPA is not a Cabinet department, but the administrator is normally given cabinet rank. The EPA has its headquarters in Washington, D. C. regional offices for each of the ten regions. The agency conducts environmental assessment, research, and education and it has the responsibility of maintaining and enforcing national standards under a variety of environmental laws, in consultation with state, tribal, and local governments. It delegates some permitting, monitoring, and enforcement responsibility to U. S. states, EPA enforcement powers include fines, sanctions, and other measures. The agency also works with industries and all levels of government in a variety of voluntary pollution prevention programs. In 2016, the agency had 15,376 full-time employees, more than half of EPAs employees are engineers, scientists, and environmental protection specialists, other employees include legal, public affairs, financial, and information technologists. Beginning in the late 1950s and through the 1960s, Congress reacted to increasing concern about the impact that human activity could have on the environment. Senator James E. Murray introduced a bill, the Resources and Conservation Act of 1959, the 1962 publication of Silent Spring by Rachel Carson alerted the public about the detrimental effects on the environment of the indiscriminate use of pesticides. In the years following, similar bills were introduced and hearings were held to discuss the state of the environment, in the colloquium, some members of Congress expressed a continuing concern over federal agency actions affecting the environment. The National Environmental Policy Act of 1969 was modeled on RCA, President Nixon signed NEPA into law on January 1,1970. The law created the Council on Environmental Quality in the Executive Office of the President, NEPA required that a detailed statement of environmental impacts be prepared for all major federal actions significantly affecting the environment. The detailed statement would ultimately be referred to as an impact statement. On July 9,1970, Nixon proposed a reorganization that consolidated many environmental responsibilities of the federal government under one agency. After conducting hearings during that summer, the House and Senate approved the proposal, the agency’s first administrator, William Ruckelshaus, took the oath of office on December 4,1970. In May 2013, Congress renamed the EPA headquarters as the William Jefferson Clinton Federal Building, the EPA is led by an Administrator of the Environmental Protection Agency. As of 2017 Scott Pruitt is the 14th administrator, each EPA regional office is responsible within its states for implementing the Agencys programs, except those programs that have been specifically delegated to states
10.
Iron
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Iron is a chemical element with symbol Fe and atomic number 26. It is a metal in the first transition series and it is by mass the most common element on Earth, forming much of Earths outer and inner core. It is the fourth most common element in the Earths crust, like the other group 8 elements, ruthenium and osmium, iron exists in a wide range of oxidation states, −2 to +6, although +2 and +3 are the most common. Elemental iron occurs in meteoroids and other low oxygen environments, but is reactive to oxygen, fresh iron surfaces appear lustrous silvery-gray, but oxidize in normal air to give hydrated iron oxides, commonly known as rust. Unlike the metals that form passivating oxide layers, iron oxides occupy more volume than the metal and thus flake off, Iron metal has been used since ancient times, although copper alloys, which have lower melting temperatures, were used even earlier in human history. Pure iron is soft, but is unobtainable by smelting because it is significantly hardened and strengthened by impurities, in particular carbon. A certain proportion of carbon steel, which may be up to 1000 times harder than pure iron. Crude iron metal is produced in blast furnaces, where ore is reduced by coke to pig iron, further refinement with oxygen reduces the carbon content to the correct proportion to make steel. Steels and iron alloys formed with metals are by far the most common industrial metals because they have a great range of desirable properties. Iron chemical compounds have many uses, Iron oxide mixed with aluminium powder can be ignited to create a thermite reaction, used in welding and purifying ores. Iron forms binary compounds with the halogens and the chalcogens, among its organometallic compounds is ferrocene, the first sandwich compound discovered. Iron plays an important role in biology, forming complexes with oxygen in hemoglobin and myoglobin. Iron is also the metal at the site of many important redox enzymes dealing with cellular respiration and oxidation and reduction in plants. A human male of average height has about 4 grams of iron in his body and this iron is distributed throughout the body in hemoglobin, tissues, muscles, bone marrow, blood proteins, enzymes, ferritin, hemosiderin, and transport in plasma. The mechanical properties of iron and its alloys can be evaluated using a variety of tests, including the Brinell test, Rockwell test, the data on iron is so consistent that it is often used to calibrate measurements or to compare tests. An increase in the content will cause a significant increase in the hardness. Maximum hardness of 65 Rc is achieved with a 0. 6% carbon content, because of the softness of iron, it is much easier to work with than its heavier congeners ruthenium and osmium. Because of its significance for planetary cores, the properties of iron at high pressures and temperatures have also been studied extensively
11.
Steel
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Steel is an alloy of iron and other elements, primarily carbon, that is widely used in construction and other applications because of its high tensile strength and low cost. Steels base metal is iron, which is able to take on two forms, body centered cubic and face centered cubic, depending on its temperature. It is the interaction of those allotropes with the elements, primarily carbon. In the body-centred cubic arrangement, there is an atom in the centre of each cube. Carbon, other elements, and inclusions within iron act as hardening agents that prevent the movement of dislocations that otherwise occur in the lattices of iron atoms. The carbon in steel alloys may contribute up to 2. 1% of its weight. Steels strength compared to pure iron is possible at the expense of irons ductility. With the invention of the Bessemer process in the mid-19th century and this was followed by Siemens-Martin process and then Gilchrist-Thomas process that refined the quality of steel. With their introductions, mild steel replaced wrought iron, further refinements in the process, such as basic oxygen steelmaking, largely replaced earlier methods by further lowering the cost of production and increasing the quality of the product. Today, steel is one of the most common materials in the world and it is a major component in buildings, infrastructure, tools, ships, automobiles, machines, appliances, and weapons. Modern steel is generally identified by various grades defined by assorted standards organizations, the noun steel originates from the Proto-Germanic adjective stakhlijan, which is related to stakhla. The carbon content of steel is between 0. 002% and 2. 1% by weight for plain iron–carbon alloys and these values vary depending on alloying elements such as manganese, chromium, nickel, iron, tungsten, carbon and so on. Basically, steel is an alloy that does not undergo eutectic reaction. In contrast, cast iron does undergo eutectic reaction, too little carbon content leaves iron quite soft, ductile, and weak. Carbon contents higher than those of steel make an alloy, commonly called pig iron, while iron alloyed with carbon is called carbon steel, alloy steel is steel to which other alloying elements have been intentionally added to modify the characteristics of steel. Common alloying elements include, manganese, nickel, chromium, molybdenum, boron, titanium, vanadium, tungsten, cobalt, and niobium. Additional elements are important in steel, phosphorus, sulfur, silicon, and traces of oxygen, nitrogen, and copper. Alloys with a higher than 2. 1% carbon content, depending on other element content, cast iron is not malleable even when hot, but it can be formed by casting as it has a lower melting point than steel and good castability properties
12.
Copper
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Copper is a chemical element with symbol Cu and atomic number 29. It is a soft, malleable, and ductile metal with high thermal and electrical conductivity. A freshly exposed surface of copper has a reddish-orange color. Copper is one of the few metals that occur in nature in directly usable metallic form as opposed to needing extraction from an ore and this led to very early human use, from c.8000 BC. Copper used in buildings, usually for roofing, oxidizes to form a green verdigris, Copper is sometimes used in decorative art, both in its elemental metal form and in compounds as pigments. Copper compounds are used as agents, fungicides, and wood preservatives. Copper is essential to all living organisms as a trace dietary mineral because it is a key constituent of the enzyme complex cytochrome c oxidase. In molluscs and crustaceans, copper is a constituent of the blood pigment hemocyanin, replaced by the hemoglobin in fish. In humans, copper is found mainly in the liver, muscle, the adult body contains between 1.4 and 2.1 mg of copper per kilogram of body weight. The filled d-shells in these elements contribute little to interatomic interactions, unlike metals with incomplete d-shells, metallic bonds in copper are lacking a covalent character and are relatively weak. This observation explains the low hardness and high ductility of single crystals of copper, at the macroscopic scale, introduction of extended defects to the crystal lattice, such as grain boundaries, hinders flow of the material under applied stress, thereby increasing its hardness. For this reason, copper is supplied in a fine-grained polycrystalline form. The softness of copper partly explains its high conductivity and high thermal conductivity. The maximum permissible current density of copper in open air is approximately 3. 1×106 A/m2 of cross-sectional area, Copper is one of a few metallic elements with a natural color other than gray or silver. Pure copper is orange-red and acquires a reddish tarnish when exposed to air, as with other metals, if copper is put in contact with another metal, galvanic corrosion will occur. A green layer of verdigris can often be seen on old structures, such as the roofing of many older buildings. Copper tarnishes when exposed to sulfur compounds, with which it reacts to form various copper sulfides. There are 29 isotopes of copper, 63Cu and 65Cu are stable, with 63Cu comprising approximately 69% of naturally occurring copper, both have a spin of 3⁄2
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