1.
Ming dynasty
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The Ming dynasty was the ruling dynasty of China – then known as the Empire of the Great Ming – for 276 years following the collapse of the Mongol-led Yuan dynasty. The Ming, described by some as one of the greatest eras of orderly government, although the primary capital of Beijing fell in 1644 to a rebellion led by Li Zicheng, regimes loyal to the Ming throne – collectively called the Southern Ming – survived until 1683. He rewarded his supporters and employed them as a counterweight against the Confucian scholar-bureaucrats. One, Zheng He, led seven enormous voyages of exploration into the Indian Ocean as far as Arabia, the rise of new emperors and new factions diminished such extravagances, the capture of the Zhengtong Emperor during the 1449 Tumu Crisis ended them completely. The imperial navy was allowed to fall into disrepair while forced labor constructed the Liaodong palisade, haijin laws intended to protect the coasts from Japanese pirates instead turned many into smugglers and pirates themselves. The growth of Portuguese, Spanish, and Dutch trade created new demand for Chinese products and produced an influx of Japanese. This abundance of specie remonetized the Ming economy, whose money had suffered repeated hyperinflation and was no longer trusted. While traditional Confucians opposed such a prominent role for commerce and the newly rich it created, combined with crop failure, floods, and epidemic, the dynasty collapsed before the rebel leader Li Zicheng, who was defeated by the Manchu-led Eight Banner armies who founded the Qing dynasty. The Mongol-led Yuan dynasty ruled before the establishment of the Ming dynasty, consequently, agriculture and the economy were in shambles, and rebellion broke out among the hundreds of thousands of peasants called upon to work on repairing the dykes of the Yellow River. A number of Han Chinese groups revolted, including the Red Turbans in 1351, the Red Turbans were affiliated with the White Lotus, a Buddhist secret society. Zhu Yuanzhang was a peasant and Buddhist monk who joined the Red Turbans in 1352. In 1356, Zhus rebel force captured the city of Nanjing, with the Yuan dynasty crumbling, competing rebel groups began fighting for control of the country and thus the right to establish a new dynasty. In 1363, Zhu Yuanzhang eliminated his archrival and leader of the rebel Han faction, Chen Youliang, in the Battle of Lake Poyang, arguably the largest naval battle in history. Known for its ambitious use of ships, Zhus force of 200,000 Ming sailors were able to defeat a Han rebel force over triple their size, claimed to be 650. The victory destroyed the last opposing rebel faction, leaving Zhu Yuanzhang in uncontested control of the bountiful Yangtze River Valley, Zhu Yuanzhang took Hongwu, or Vastly Martial, as his era name. Hongwu made an effort to rebuild state infrastructure. He built a 48 km long wall around Nanjing, as well as new palaces, Hongwu organized a military system known as the weisuo, which was similar to the fubing system of the Tang dynasty. With a growing suspicion of his ministers and subjects, Hongwu established the Jinyiwei, some 100,000 people were executed in a series of purges during his rule
2.
Porcelain
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Porcelain /ˈpɔːrsəlᵻn, ˈpɔːrslᵻn/ is a ceramic material made by heating materials, generally including kaolin, in a kiln to temperatures between 1,200 and 1,400 °C. Porcelain was first developed in China around 2,000 years ago, then spread to other East Asian countries, and finally Europe. It combines well with both glazes and paint, and can be modelled very well, allowing a range of decorative treatments in tablewares, vessels. It also has uses in technology and industry. The European name, porcelain in English, come from the old Italian porcellana because of its resemblance to the translucent surface of the shell, Porcelain is also referred to as china or fine china in some English-speaking countries, as it was first seen in imports from China. Porcelain has been described as being completely vitrified, hard, impermeable, white or artificially coloured, translucent, however, the term porcelain lacks a universal definition and has been applied in a very unsystematic fashion to substances of diverse kinds which have only certain surface-qualities in common. Terms such as porcellaneous or near-porcelain may be used in such cases, a high proportion of modern porcelain is made of the variant bone china. Kaolin is the material from which porcelain is made, even though clay minerals might account for only a small proportion of the whole. The word paste is an old term for both the unfired and fired material, a more common terminology these days for the unfired material is body, for example, when buying materials a potter might order an amount of porcelain body from a vendor. The composition of porcelain is highly variable, but the mineral kaolinite is often a raw material. Other raw materials can include feldspar, ball clay, glass, bone ash, steatite, quartz, petuntse, the clays used are often described as being long or short, depending on their plasticity. Long clays are cohesive and have high plasticity, short clays are cohesive and have lower plasticity. Clays used for porcelain are generally of lower plasticity and are shorter than many other pottery clays and they wet very quickly, meaning that small changes in the content of water can produce large changes in workability. Thus, the range of content within which these clays can be worked is very narrow. The following section provides information on the methods used to form, decorate, finish, glaze. Many types of glaze, such as the iron-containing glaze used on the wares of Longquan, were designed specifically for their striking effects on porcelain. Porcelain wares may be decorated under the glaze using pigments that include cobalt and copper or over the glaze using coloured enamels. Like many earlier wares, modern porcelains are often biscuit-fired at around 1,000 °C, coated with glaze, another early method is once-fired where the glaze is applied to the unfired body and the two fired together in a single operation
3.
Fire test
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A fire test is a means of determining whether fire protection products meet minimum performance criteria as set out in a building code or other applicable legislation. Successful tests in laboratories holding national accreditation for testing and certification result in the issuance of a certification listing, the listing is public domain, whereas the test report itself is proprietary information belonging to the test sponsor. There are many different types of fire tests apart from those on firestops, walls and floors themselves can be tested, closures within them, such as windows, fire doors, fire dampers, structural steel, and more. Fire tests are conducted both on fire protection and on passive fire protection items. Each have different test methods and scales, there are full scale, small scale and bench scale tests. There are tests on systems, such as the one below, fire testing must consider all applicable provisions of the intended product certification. It is also prudent to test products in such a manner as to ease of use and broad, economical applications with regards to listing and approval use. Tests can be bench scale, medium scale, or full scale, typical information gathered from full scale testing is heat release rate vs. time, smoke production and species composition, radiant heat, and interaction with fire control or suppression systems. Many fire tests are run by official laboratories for the purpose of product certification, some universities have functioning fire research groups which are equipped to run fire tests on building materials. The below photos illustrate types of testing as seen in the United States. Brown to the Nuclear Regulatory Commission, watchdog groups, and the press
4.
Fire brick
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A fire brick, firebrick, or refractory brick is a block of refractory ceramic material used in lining furnaces, kilns, fireboxes, and fireplaces. A refractory brick is built primarily to high temperature. In other, less harsh situations, such as in an electric or natural gas fired kiln, more porous bricks and they are weaker, but they are much lighter, easier to form, and insulate far better than dense bricks. In any case, firebricks should not spall, and their strength should hold up well during rapid temperature changes, in the making of firebrick, fireclay is fired in the kiln until it is partly vitrified, and for special purposes may also be glazed. There are two sizes of fire-brick, one is 9×4 1⁄2×3 inches and the other is 9×4 1⁄2×2 1⁄2 inches. Also available are firebrick splits which are half the thickness and are used to line wood stoves. The dimensions of a split are usually 9×4 1⁄2×1 1⁄4 inches, fire bricks have an Aluminium oxide content that can be as high as 50-80%. The silica firebricks that line steel-making furnaces are used at temperatures up to 1648°C, which would melt many other types of ceramic, high-temperature Reusable Surface Insulation, a material with the same composition, was used in the insulating tiles of the Space Shuttle. Non-ferrous metallurgical processes use basic refractory bricks because the used in these processes readily dissolve the acidic silica bricks. The most common basic refractory bricks using in smelting non-ferrous metal concentrates are chrome–magnesite or magnesite-chrome bricks, a range of other materials find use as firebricks for lower temperature applications. Magnesium oxide is used as a lining for furnaces. Silica bricks are the most common type of bricks used for the lining of furnaces. As the inner lining is usually of sacrificial nature, fire bricks of higher alumina content may be employed to lengthen the duration between re-linings, very often cracks can be seen in this sacrificial inner lining shortly after being put into operation. They revealed more expansion joints should have put in the first place. Silicon carbide, with high strength, is a popular material for hearths of incinerators and cremators. Common red clay brick are used for chimneys and wood-fired ovens
5.
High-temperature insulation wool
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The first variety, aluminium silicate fibre, developed in the 1950s, was referred to as refractory ceramic fibre. Due to the production, and limited availability compared to mineral wool, HTIW products are almost only used in high temperature industrial applications. Humans have used fire for melting and heat treating metals for thousands of years, to ensure safe working with the fire, for melting and working metals, special refractory materials were needed to enable the handling of liquid or hot metals. For decades, however, other materials have been used for thermal insulation, glass wool. In the 1960s aluminium-silicate-based refractory ceramic fibre were launched on the market in Europe, due to their high temperature-resistance and good technical properties, they quickly became the reference for industrial high temperature insulation. Due to the development of new types the nomenclature of high-temperature insulation wool was redefined in Germany at the end of the 1990s. Although even today the term ceramic fibre or refractory ceramic fibre is used it is inaccurate in terms of the materials available, their specific properties. Thermal insulation with HTIW enabled a more lightweight construction of industrial furnaces and other equipment, resulting in many economic. Consequences are smaller wall thicknesses and considerably lower lining masses, comparison of the mass for the different wall linings Heavyweight lining, 1500–3500 kg/m³, Lightweight lining, 500–1000 kg/m³, Lining with HTIW, 160–300 kg/m³. High-temperature insulation wool is an accumulation of fibres of different lengths and diameters, the group of the HTIWs include amorphous alkaline earth silicate wool and alumino silicate wool as well as polycrystalline wool with a classification temperatures >1000 °C. Besides the differences in the composition, manmade fibres have parallel edges in contrast to natural fibres. Also known as glass wool, AES Wool consist of amorphous fibres. Products made from AES are generally used at temperatures less than 900 °C and in continuously operating equipment. Alumino silicate wool, also known as “refractory ceramic fibre”, are amorphous fibres produced by melting a combination of Al2O3 and SiO2, products made of Alumino Silicate Wool are generally used at application temperatures >900°C and in intermittently operating equipment and critical application conditions. Polycrystalline wool consists of fibres containing greater than 70 wt. % Al2O3, the water-soluble green fibres obtained as a precursor are crystallized by means of heat treatment. Polycrystalline Wool is generally used at temperatures greater than 1300 °C and in critical chemical and physical application conditions. Registration, Evaluation, Authorisation and Restriction of Chemicals is a European Union regulation of 18 December 2006, REACH addresses the production and use of chemical substances, and their potential impacts on both human health and the environment. A Substance Information Exchange Forum has been set up for each type of HITW, AES, ASW and PCW have been registered before the first deadline of 1 December 2010 and can therefore be used on the European market
6.
Dome of the Rock
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The Dome of the Rock is an Islamic shrine located on the Temple Mount in the Old City of Jerusalem. The original dome collapsed in 1015 and was rebuilt in 1022–23, the Dome of the Rock is in its core one of the oldest extant works of Islamic architecture. The octagonal plan of the structure may also have influenced by the Byzantine Church of the Seat of Mary built between 451 and 458 on the road between Jerusalem and Bethlehem. Herods Temple was destroyed in 70 CE by the Romans, and after the Bar Kokhba revolt in 135 CE, Jerusalem was ruled by the Christian Byzantine Empire throughout the 4th to 6th centuries. During this time, Christian pilgrimage to Jerusalem began to develop, the Church of the Holy Sepulchre was built under Constantine in the 320s, but the Temple Mount was left undeveloped after a failed project of restoration of the temple under Julian the Apostate. The Dome of the Rock is now assumed to have been built by the order of Umayyad Caliph Abd al-Malik and his son. According to Sibt ibn al-Jawzi, construction started in 687, construction cost was reportedly seven times the yearly tax income of Egypt. A dedicatory inscription in Kufic script is preserved inside the dome, the date is recorded as AH72, the year historians believe the construction of the original Dome was completed. In this inscription, the name of al-Malik was deleted and replaced by the name of Abbasid caliph Al-Mamun and this alteration of the original inscription was first noted by Melchior de Vogüé in 1864. Some scholars have suggested that the dome was added to a building, built either by Muawiyah I, or indeed a Byzantine building dating to before the Muslim conquest. Its architecture and mosaics were patterned after nearby Byzantine churches and palaces, the two engineers in charge of the project were Raja ibn Haywah, a Muslim theologian from Beit Shean and Yazid Ibn Salam, a non-Arab who was Muslim and a native of Jerusalem. Creswell in his book The Origin of the Plan of the Dome of the Rock notes that those who built the shrine used the measurements of the Church of the Holy Sepulchre. The diameter of the dome of the shrine is 20.20 m and its height 20.48 m, while the diameter of the dome of the Church of the Holy Sepulchre is 20.90 m and its height 21.05 m. It comprises a dome, approximately 20 m in diameter. Surrounding this circle is an arcade of 24 piers and columns. The original construction was surrounded by arcades, like the Dome of the Chain. Under Abbasid caliph Al-Mamun, a wall was added. The building was damaged by earthquakes in 808 and again in 846
7.
Jerusalem
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Jerusalem is a city located on a plateau in the Judaean Mountains between the Mediterranean and the Dead Sea. It is considered a city in the three major Abrahamic religions of Judaism, Christianity and Islam. During its long history, Jerusalem has been destroyed at least twice, besieged 23 times, attacked 52 times, the part of Jerusalem called the City of David was settled in the 4th millennium BCE. In 1538, walls were built around Jerusalem under Suleiman the Magnificent, today those walls define the Old City, which has been traditionally divided into four quarters—known since the early 19th century as the Armenian, Christian, Jewish, and Muslim Quarters. The Old City became a World Heritage Site in 1981, and is on the List of World Heritage in Danger, Modern Jerusalem has grown far beyond the Old Citys boundaries. These foundational events, straddling the dawn of the 1st millennium BCE, the sobriquet of holy city was probably attached to Jerusalem in post-exilic times. The holiness of Jerusalem in Christianity, conserved in the Septuagint which Christians adopted as their own authority, was reinforced by the New Testament account of Jesuss crucifixion there, in Sunni Islam, Jerusalem is the third-holiest city, after Mecca and Medina. As a result, despite having an area of only 0, outside the Old City stands the Garden Tomb. Today, the status of Jerusalem remains one of the issues in the Israeli–Palestinian conflict. During the 1948 Arab–Israeli War, West Jerusalem was among the captured and later annexed by Israel while East Jerusalem, including the Old City, was captured. Israel captured East Jerusalem from Jordan during the 1967 Six-Day War and subsequently annexed it into Jerusalem, one of Israels Basic Laws, the 1980 Jerusalem Law, refers to Jerusalem as the countrys undivided capital. All branches of the Israeli government are located in Jerusalem, including the Knesset, the residences of the Prime Minister and President, the international community does not recognize Jerusalem as Israels capital, and the city hosts no foreign embassies. Jerusalem is also home to some non-governmental Israeli institutions of importance, such as the Hebrew University. In 2011, Jerusalem had a population of 801,000, of which Jews comprised 497,000, Muslims 281,000, a city called Rušalim in the Execration texts of the Middle Kingdom of Egypt is widely, but not universally, identified as Jerusalem. Jerusalem is called Urušalim in the Amarna letters of Abdi-Heba, the name Jerusalem is variously etymologized to mean foundation of the god Shalem, the god Shalem was thus the original tutelary deity of the Bronze Age city. The form Yerushalem or Yerushalayim first appears in the Bible, in the Book of Joshua, according to a Midrash, the name is a combination of Yhwh Yireh and the town Shalem. The earliest extra-biblical Hebrew writing of the word Jerusalem is dated to the sixth or seventh century BCE and was discovered in Khirbet Beit Lei near Beit Guvrin in 1961. The inscription states, I am Yahweh thy God, I will accept the cities of Judah and I will redeem Jerusalem, or as other scholars suggest, the mountains of Judah belong to him, to the God of Jerusalem
8.
Ottoman Empire
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After 1354, the Ottomans crossed into Europe, and with the conquest of the Balkans the Ottoman Beylik was transformed into a transcontinental empire. The Ottomans ended the Byzantine Empire with the 1453 conquest of Constantinople by Mehmed the Conqueror, at the beginning of the 17th century the empire contained 32 provinces and numerous vassal states. Some of these were later absorbed into the Ottoman Empire, while others were granted various types of autonomy during the course of centuries. With Constantinople as its capital and control of lands around the Mediterranean basin, while the empire was once thought to have entered a period of decline following the death of Suleiman the Magnificent, this view is no longer supported by the majority of academic historians. The empire continued to maintain a flexible and strong economy, society, however, during a long period of peace from 1740 to 1768, the Ottoman military system fell behind that of their European rivals, the Habsburg and Russian Empires. While the Empire was able to hold its own during the conflict, it was struggling with internal dissent. Starting before World War I, but growing increasingly common and violent during it, major atrocities were committed by the Ottoman government against the Armenians, Assyrians and Pontic Greeks. The word Ottoman is an anglicisation of the name of Osman I. Osmans name in turn was the Turkish form of the Arabic name ʿUthmān, in Ottoman Turkish, the empire was referred to as Devlet-i ʿAlīye-yi ʿOsmānīye, or alternatively ʿOsmānlı Devleti. In Modern Turkish, it is known as Osmanlı İmparatorluğu or Osmanlı Devleti, the Turkish word for Ottoman originally referred to the tribal followers of Osman in the fourteenth century, and subsequently came to be used to refer to the empires military-administrative elite. In contrast, the term Turk was used to refer to the Anatolian peasant and tribal population, the term Rūmī was also used to refer to Turkish-speakers by the other Muslim peoples of the empire and beyond. In Western Europe, the two names Ottoman Empire and Turkey were often used interchangeably, with Turkey being increasingly favored both in formal and informal situations and this dichotomy was officially ended in 1920–23, when the newly established Ankara-based Turkish government chose Turkey as the sole official name. Most scholarly historians avoid the terms Turkey, Turks, and Turkish when referring to the Ottomans, as the power of the Seljuk Sultanate of Rum declined in the 13th century, Anatolia was divided into a patchwork of independent Turkish principalities known as the Anatolian Beyliks. One of these beyliks, in the region of Bithynia on the frontier of the Byzantine Empire, was led by the Turkish tribal leader Osman, osmans early followers consisted both of Turkish tribal groups and Byzantine renegades, many but not all converts to Islam. Osman extended the control of his principality by conquering Byzantine towns along the Sakarya River and it is not well understood how the early Ottomans came to dominate their neighbours, due to the scarcity of the sources which survive from this period. One school of thought which was popular during the twentieth century argued that the Ottomans achieved success by rallying religious warriors to fight for them in the name of Islam, in the century after the death of Osman I, Ottoman rule began to extend over Anatolia and the Balkans. Osmans son, Orhan, captured the northwestern Anatolian city of Bursa in 1326 and this conquest meant the loss of Byzantine control over northwestern Anatolia. The important city of Thessaloniki was captured from the Venetians in 1387, the Ottoman victory at Kosovo in 1389 effectively marked the end of Serbian power in the region, paving the way for Ottoman expansion into Europe
9.
Brooklyn Museum
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The Brooklyn Museum is an art museum located in the New York City borough of Brooklyn. At 560,000 square feet, the museum is New York Citys third largest in physical size, the museum initially struggled to maintain its building and collection, only to be revitalized in the late 20th century, thanks to major renovations. Significant areas of the collection include antiquities, specifically their collection of Egyptian antiquities spanning over 3,000 years, African, Oceanic, and Japanese art make for notable antiquities collections as well. American art is represented, starting at the Colonial period. Artists represented in the collection include Mark Rothko, Edward Hopper, Norman Rockwell, Winslow Homer, Edgar Degas, Georgia OKeeffe, the museum also has a Memorial Sculpture Garden which features salvaged architectural elements from throughout New York City. The roots of the Brooklyn Museum extend back to the 1823 founding by Augustus Graham of the Brooklyn Apprentices’ Library in Brooklyn Heights, in 1890, under its director Franklin Hooper, Institute leaders reorganized as the Brooklyn Institute of Arts and Sciences and began planning the Brooklyn Museum. The initial design for the Brooklyn Museum was four times as large as the actualized version, Daniel Chester French, the noted sculptor of the Lincoln Memorial, was the principal designer of the pediment sculptures and the monolithic 12. 5-foot figures along the cornice. The figures were created by 11 sculptors and carved by the Piccirilli Brothers, by 1920, the New York City Subway reached the museum with a subway station, this greatly improved access to the once-isolated museum from Manhattan and other outer boroughs. The Brooklyn Institutes director Franklin Hooper was the museums first director and he was followed by Philip Newell Youtz, Laurance Page Roberts, Isabel Spaulding Roberts, Charles Nagel, Jr. and Edgar Craig Schenck. Thomas S. Buechner became the director in 1960, making him one of the youngest directors in the country. Buechner oversaw a major transformation in the way the museum displayed art and brought some one thousand works that had languished in the museums archives and put them on display. Buechner played a role in rescuing the Daniel Chester French sculptures from destruction due to an expansion project at the Manhattan Bridge in the 1960s. The Brooklyn Museum changed its name to Brooklyn Museum of Art in 1997, on March 12,2004, the museum announced that it would revert to its previous name. In April 2004, the museum opened the James Polshek-designed entrance pavilion on the Eastern Parkway façade, in September 2014, Lehman announced that he was planning to retire around June 2015. In May 2015, Creative Time president and artistic director Anne Pasternak was named the Museums next director, member institutions occupy land or buildings owned by the City of New York and derive part of their yearly funding from the City. The Brooklyn Museum also supplements its earned income with funding from Federal and State governments, as well as donations by individuals. Major benefactors include Frank Lusk Babbott, the museum is the site of the annual Brooklyn Artists Ball which has included celebrity hosts such as Sarah Jessica Parker and Liv Tyler. The Brooklyn Museum exhibits collections that seek to embody the rich heritage of world cultures
10.
Solid
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Solid is one of the four fundamental 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 other, either in a regular geometric lattice or irregularly. The branch of physics deals with solids is called solid-state physics. Materials science is concerned with the physical and chemical properties of solids. Solid-state chemistry is concerned with the synthesis of novel materials, as well as the science of identification. The atoms, molecules or ions which make up solids may be arranged in a repeating pattern. Materials whose constituents are arranged in a regular pattern are known as crystals, in some cases, the regular ordering can continue unbroken over a large scale, for example diamonds, where each diamond is a single crystal. Almost all common metals, and many ceramics, are polycrystalline, in other materials, there is no long-range order in the position of the atoms. These solids are known as amorphous solids, examples include polystyrene, whether a solid is crystalline or amorphous depends on the material involved, and the conditions in which it was formed. Solids which are formed by slow cooling will tend to be crystalline, likewise, the specific crystal structure adopted by a crystalline solid depends on the material involved and on how it was formed. While many common objects, such as an ice cube or a coin, are chemically identical throughout, for example, a typical rock is an aggregate of several different minerals and mineraloids, with no specific chemical composition. Wood is an organic material consisting primarily of cellulose fibers embedded in a matrix of organic lignin. In materials science, composites of more than one constituent material can be designed to have desired properties, the forces between the atoms in a solid can take a variety of forms. For example, a crystal of sodium chloride is made up of sodium and chlorine. In diamond or silicon, the atoms share electrons and form covalent bonds, in metals, electrons are shared in metallic bonding. Some solids, particularly most organic compounds, are together with van der Waals forces resulting from the polarization of the electronic charge cloud on each molecule. The dissimilarities between the types of solid result from the differences between their bonding, metals typically are strong, dense, and good conductors of both electricity and heat
11.
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
12.
Nonmetal
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In chemistry, a nonmetal is a chemical element that mostly lacks metallic attributes. Seventeen elements are classified as nonmetals, most are gases, one is a liquid. Moving rightward across the standard form of the table, nonmetals adopt structures that have progressively fewer nearest neighbours. Polyatomic nonmetals have structures with either three nearest neighbours, as is the case with carbon, or two nearest neighbours in the case of sulfur, diatomic nonmetals, such as hydrogen, have one nearest neighbour, and the monatomic noble gases, such as helium, have none. This gradual fall in the number of nearest neighbours is associated with a reduction in metallic character, the distinction between the three categories of nonmetals, in terms of receding metallicity is not absolute. Boundary overlaps occur as outlying elements in each category show less-distinct, living organisms are also composed almost entirely of nonmetals, and nonmetals form many more compounds than metals. There is no definition of a nonmetal. They show more variability in their properties than metals do, the following are some of the chief characteristics of nonmetals. The elements generally classified as nonmetals include one element in group 1, one in group 14, the distinction between nonmetals and metals is by no means clear. Nonmetals have structures in each atom usually forms bonds with nearest neighbours. Each atom is able to complete its valence shell and attain a stable noble gas configuration. Exceptions to the rule occur with hydrogen, carbon, nitrogen and oxygen, atoms of the latter three elements are sufficiently small such that they are able to form alternative bonding structures, with fewer nearest neighbours. Thus, carbon is able to form its layered graphite structure, the larger size of the remaining non-noble nonmetals weakens their capacity to form multiple bonds and they instead form two or more single bonds to two or more different atoms. Sulfur, for example, forms an eight-membered molecule in which the atoms are arranged in a ring, a similar pattern occurs more generally, at the level of the entire periodic table, in comparing metals and nonmetals. There is a transition from metallic bonding among the metals on the left of the table through to covalent or Van der Waals bonding among the nonmetals on the right of the table, metallic bonding tends to involve close-packed centrosymmetric structures with a high number of nearest neighbours. Post-transition metals and metalloids, sandwiched between the metals and the nonmetals, tend to have more complex structures with an intermediate number of nearest neighbours. Nonmetallic bonding, towards the right of the table, features open-packed directional structures with fewer or zero nearest neighbours, as is the case with the major categories of metals, metalloids and nonmetals, there is some variation and overlapping of properties within and across each category of nonmetal. Among the polyatomic nonmetals, carbon, phosphorus and selenium—which border the metalloids—begin to show some metallic character, sulfur, is the least metallic of the polyatomic nonmetals but even here shows some discernible metal-like character
13.
Metalloid
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A metalloid is any chemical element which has properties in between those of metals and nonmetals, or that has a mixture of them. There is neither a standard definition of a metalloid nor complete agreement on the elements appropriately classified as such, despite the lack of specificity, the term remains in use in the literature of chemistry. The six commonly recognised metalloids are boron, silicon, germanium, arsenic, antimony, five elements are less frequently so classified, carbon, aluminium, selenium, polonium, and astatine. Typical metalloids have an appearance, but they are brittle. Chemically, they behave mostly as nonmetals and they can form alloys with metals. Most of their physical and chemical properties are intermediate in nature. Metalloids are usually too brittle to have any structural uses and they and their compounds are used in alloys, biological agents, catalysts, flame retardants, glasses, optical storage and optoelectronics, pyrotechnics, semiconductors, and electronics. The electrical properties of silicon and germanium enabled the establishment of the industry in the 1950s. The term metalloid originally referred to nonmetals and its more recent meaning, as a category of elements with intermediate or hybrid properties, became widespread in 1940–1960. Metalloids sometimes are called semimetals, a practice that has been discouraged, in physics it more specifically refers to the electronic band structure of a substance. A metalloid is an element with properties in between, or that are a mixture of, those of metals and nonmetals, and which is hard to classify as either a metal or a nonmetal. This is a definition that draws on metalloid attributes consistently cited in the literature. Difficulty of categorisation is a key attribute, most elements have a mixture of metallic and nonmetallic properties, and can be classified according to which set of properties is more pronounced. Only the elements at or near the margins, lacking a sufficiently clear preponderance of either metallic or nonmetallic properties, are classified as metalloids, boron, silicon, germanium, arsenic, antimony, and tellurium are recognised commonly as metalloids. Depending on the author, one or more from selenium, polonium, boron sometimes is excluded, by itself, or with silicon. Sometimes tellurium is not regarded as a metalloid, the inclusion of antimony, polonium, and astatine as metalloids also has been questioned. Other elements occasionally are classified as metalloids and these elements include hydrogen, beryllium, nitrogen, phosphorus, sulfur, zinc, gallium, tin, iodine, lead, bismuth, and radon. The p-block metals, and nonmetals that can form alloys with metals or modify their properties also have occasionally considered as metalloids
14.
Ionic bonding
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Ionic bonding is a type of chemical bond that involves the electrostatic attraction between oppositely charged ions, and is the primary interaction occurring in ionic compounds. The ions are atoms that have gained one or more electrons and this transfer of electrons is known as electrovalence in contrast to covalence. In the simplest case, the cation is an atom and the anion is a nonmetal atom. In simpler words, a bond is the transfer of electrons from a metal to a non-metal in order for both atoms to obtain a full valence shell. Bonds with partially ionic and partially covalent character are called polar covalent bonds, Ionic compounds conduct electricity when molten or in solution, typically as a solid. Ionic compounds generally have a melting point, depending on the charge of the ions they consist of. The higher the charges the stronger the forces and the higher the melting point. They also tend to be soluble in water, here, the opposite trend roughly holds, the weaker the cohesive forces, the greater the solubility. Atoms that have an almost full or almost empty valence shell tend to be very reactive, atoms that are strongly electronegative often have only one or two empty orbitals in their valence shell, and frequently bond with other molecules or gain electrons to form anions. Atoms that are weakly electronegative have relatively few valence electrons that can easily be shared with atoms that are strongly electronegative, as a result, weakly electronegative atoms tend to distort their electrons cloud and form cations. Ionic bonding can result from a reaction when atoms of an element, whose ionization energy is low. In doing so, cations are formed, the atom of another element, whose electron affinity is positive, then accepts the electron, again to attain a stable electron configuration, and after accepting electron the atom becomes an anion. Typically, the electron configuration is one of the noble gases for elements in the s-block and the p-block. The electrostatic attraction between the anions and cations leads to the formation of a solid with a lattice in which the ions are stacked in an alternating fashion. In such a lattice, it is not possible to distinguish discrete molecular units. However, the ions themselves can be complex and form molecular ions like the acetate anion or the ammonium cation, for example, common table salt is sodium chloride. When sodium and chlorine are combined, the sodium atoms each lose an electron, forming cations, and these ions are then attracted to each other in a 1,1 ratio to form sodium chloride. For compounds that are transitional to the alloys and possess mixed ionic and metallic bonding, many sulfides, e. g. do form non-stoichiometric compounds
15.
Covalent bond
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A covalent bond, also called a molecular bond, is a chemical bond that involves the sharing of electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs, for many molecules, the sharing of electrons allows each atom to attain the equivalent of a full outer shell, corresponding to a stable electronic configuration. Covalent bonding includes many kinds of interactions, including σ-bonding, π-bonding, metal-to-metal bonding, agostic interactions, bent bonds, the term covalent bond dates from 1939. In the molecule H2, the atoms share the two electrons via covalent bonding. Covalency is greatest between atoms of similar electronegativities, thus, covalent bonding does not necessarily require that the two atoms be of the same elements, only that they be of comparable electronegativity. Covalent bonding that entails sharing of electrons more than two atoms is said to be delocalized. The term covalence in regard to bonding was first used in 1919 by Irving Langmuir in a Journal of the American Chemical Society article entitled The Arrangement of Electrons in Atoms and Molecules. Langmuir wrote that we shall denote by the term covalence the number of pairs of electrons that an atom shares with its neighbors. The idea of covalent bonding can be traced several years before 1919 to Gilbert N. Lewis and he introduced the Lewis notation or electron dot notation or Lewis dot structure, in which valence electrons are represented as dots around the atomic symbols. Pairs of electrons located between atoms represent covalent bonds, multiple pairs represent multiple bonds, such as double bonds and triple bonds. An alternative form of representation, not shown here, has bond-forming electron pairs represented as solid lines, Lewis proposed that an atom forms enough covalent bonds to form a full outer electron shell. In the diagram of methane shown here, the atom has a valence of four and is, therefore, surrounded by eight electrons, four from the carbon itself. Each hydrogen has a valence of one and is surrounded by two electrons – its own one electron plus one from the carbon, walter Heitler and Fritz London are credited with the first successful quantum mechanical explanation of a chemical bond in 1927. Their work was based on the valence bond model, which assumes that a bond is formed when there is good overlap between the atomic orbitals of participating atoms. Atomic orbitals have specific directional properties leading to different types of covalent bonds, sigma bonds are the strongest covalent bonds and are due to head-on overlapping of orbitals on two different atoms. A single bond is usually a σ bond, pi bonds are weaker and are due to lateral overlap between p orbitals. A double bond between two given atoms consists of one σ and one π bond, and a bond is one σ. Covalent bonds are also affected by the electronegativity of the atoms which determines the chemical polarity of the bond
16.
Vitrification
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Vitrification is the transformation of a substance into a glass, that is to say a non-crystalline amorphous solid. In the production of ceramics, vitrification is responsible for its impermeability to water, Vitrification is usually achieved by heating materials until they liquidize, then cooling the liquid, often rapidly, so that it passes through the glass transition to form a vitrified solid. Certain chemical reactions also result in glasses, in a wider sense, the embedding of material in a glassy matrix is also called vitrification. An important application is the vitrification of radioactive waste to obtain a stable compound that is suitable for ultimate disposal, thermal fluctuations break the bonds, therefore, the lower the temperature, the higher the degree of connectivity. Because of that materials have a characteristic threshold temperature termed glass transition temperature. The most common applications are in the making of pottery, glass, and some types of food, Vitrification is the progressive partial fusion of a clay, or of a body, as a result of a firing process. As vitrification proceeds the proportion of glassy bond increases and the apparent porosity of the product becomes progressively lower. Vitreous bodies have open porosity, and may be opaque or translucent. In this context zero porosity, may be defined as less than 1% water absorption, however, various standard procedures define the conditions of water absorption. An example is by ASTM, who state The term vitreous generally signifies less than 0. 5% absorption, except for floor and wall tile and low-voltage electrical insulators which are considered vitreous up to 3% water absorption. Glazing alone does not make pottery impermeable to water, porcelain, bone china and sanitaryware are examples of vitrified pottery, and are impermeable even without glaze. Stoneware may be vitrified or semi-vitrified, the type would not be impermeable without glaze. When sucrose is cooled slowly it results in crystal sugar, Vitrification can also occur when starting with a liquid such as water, usually through very rapid cooling or the introduction of agents that suppress the formation of ice crystals. This is in contrast to ordinary freezing which results in ice crystal formation, additives used in cryobiology or produced naturally by organisms living in polar regions are called cryoprotectants. Cold-adapted frogs and some other ectotherms naturally produce glycerol or glucose in their livers to reduce ice formation. When glucose is used as a cryoprotectant by arctic frogs, massive amounts of glucose are released at low temperature, when the frog rewarms during spring, the extra glucose must be rapidly eliminated, but stored. Arctic insects also use sugars as cryoprotectants, arctic fish use antifreeze proteins, sometimes appended with sugars, as cryoprotectants. Ordinary soda-lime glass, used in windows and drinking containers, is created by the addition of sodium carbonate, without these additives silicon dioxide will require very high temperature to obtain a melt and subsequently a glass
17.
Amorphous solid
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In condensed matter physics and materials science, an amorphous or non-crystalline solid is a solid that lacks the long-range order that is characteristic of a crystal. In some older books, the term has been used synonymously with glass, nowadays, glassy solid or amorphous solid is considered to be the overarching concept, and glass the more special case, A glass is an amorphous solid that exhibits a glass transition. Other types of solids include gels, thin films. Amorphous materials have a structure made of interconnected structural blocks. Even amorphous materials have some shortrange order at the length scale due to the nature of chemical bonding. Furthermore, in small crystals a large fraction of the atoms are the crystal, relaxation of the surface and interfacial effects distort the atomic positions. Amorphous phases are important constituents of thin films, which are layers of a few nm to some tens of µm thickness deposited upon a substrate. For higher values, the diffusion of deposited atomic species would allow for the formation of crystallites with long range atomic order. Regarding their applications, amorphous metallic layers played an important role in the discussion of a suspected superconductivity in amorphous metals, today, optical coatings made from TiO2, SiO2, Ta2O5 etc. and combinations of them in most cases consist of amorphous phases of these compounds. Much research is carried out into thin films as a gas separating membrane layer. Also, hydrogenated amorphous silicon, a-Si, H in short, is of significance for thin film solar cells. In case of a-Si, H the missing long-range order between silicon atoms is partly induced by the presence by hydrogen in the percent range, the occurrence of amorphous phases turned out as a phenomenon of particular interest for studying thin film growth. Remarkably, the growth of polycrystalline films is used and preceded by an initial amorphous layer. The most investigated example is represented by thin multicrystalline silicon films, an initial amorphous layer was observed in many studies. The phenomenon has been interpreted in the framework of Ostwalds rule of stages that predicts the formation of phases to proceed with increasing condensation time towards increasing stability. Experimental studies of the phenomenon require a clearly defined state of the substrate surface, the Physics of Structurally Disordered Matter, An Introduction. Amorphous Solids and the Liquid State
18.
Glass
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Glass is a non-crystalline amorphous solid that is often transparent and has widespread practical, technological, and decorative usage in, for example, window panes, tableware, and optoelectronics. The most familiar, and historically the oldest, types of glass are silicate glasses based on the chemical compound silica, the primary constituent of sand. The term glass, in usage, is often used to refer only to this type of material. Many applications of silicate glasses derive from their optical transparency, giving rise to their use as window panes. Glass can be coloured by adding metallic salts, and can also be painted and printed with vitreous enamels and these qualities have led to the extensive use of glass in the manufacture of art objects and in particular, stained glass windows. Although brittle, silicate glass is extremely durable, and many examples of glass fragments exist from early glass-making cultures, because glass can be formed or moulded into any shape, it has been traditionally used for vessels, bowls, vases, bottles, jars and drinking glasses. In its most solid forms it has also used for paperweights, marbles. Some objects historically were so commonly made of glass that they are simply called by the name of the material, such as drinking glasses. Porcelains and many polymer thermoplastics familiar from everyday use are glasses and these sorts of glasses can be made of quite different kinds of materials than silica, metallic alloys, ionic melts, aqueous solutions, molecular liquids, and polymers. For many applications, like glass bottles or eyewear, polymer glasses are a lighter alternative than traditional glass, silica is a common fundamental constituent of glass. In nature, vitrification of quartz occurs when lightning strikes sand, forming hollow, fused quartz is a glass made from chemically-pure SiO2. It has excellent resistance to shock, being able to survive immersion in water while red hot. However, its high melting-temperature and viscosity make it difficult to work with, normally, other substances are added to simplify processing. One is sodium carbonate, which lowers the transition temperature. The soda makes the glass water-soluble, which is undesirable, so lime, some magnesium oxide. The resulting glass contains about 70 to 74% silica by weight and is called a soda-lime glass, soda-lime glasses account for about 90% of manufactured glass. Most common glass contains other ingredients to change its properties, lead glass or flint glass is more brilliant because the increased refractive index causes noticeably more specular reflection and increased optical dispersion. Adding barium also increases the refractive index, iron can be incorporated into glass to absorb infrared energy, for example in heat absorbing filters for movie projectors, while cerium oxide can be used for glass that absorbs UV wavelengths
19.
Earthenware
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Earthenware is glazed or unglazed nonvitreous pottery which has normally been fired below 1200°C. Porcelain, bone china and stoneware, all fired at high temperatures to vitrify, are the main other important types of pottery. Pit fired earthenware dates back to as early as 29, 000–25,000 BCE, outside East Asia, porcelain was manufactured only from the 18th century, and then initially as an expensive luxury. Earthenware, when fired, is opaque and non-vitreous, soft, the Combined Nomenclature of the European Communities describes it as being made of selected clays sometimes mixed with feldspars and varying amounts of other minerals and white or light-colored. Generally, earthenware bodies exhibit higher plasticity than most whiteware bodies and hence are easier to shape by RAM press, due to its porosity, earthenware, with a water absorption of 5-8%, must be glazed to be watertight. Earthenware has lower mechanical strength than bone china, porcelain or stoneware, darker-colored terracotta earthenwares, typically orange or red, due to a comparatively high content of iron oxide are widely used for flower pots, tiles and some decorative and oven wares. A general body formulation for contemporary earthenware is 25% kaolin, 25% ball clay, 35% quartz and 15% feldspar. Modern earthenware may be fired to temperatures between 1,000 and 1,150 °C and glost-fired to between 950 to 1,050 °C, the usual practice in factories and some studio potteries. Some studio potters follow the practice, with a low-temperature bisque firing. The firing schedule will be determined by the raw materials used, historically, such high temperatures were unattainable in most cultures and periods until modern times, though Chinese ceramics were far ahead of other cultures in this respect. Earthenware can be produced at firing temperatures as low as 600 °C, much historical pottery was fired somewhere around 800 °C, giving a wide margin of error where there was no precise way of measuring temperature, and very variable conditions within the kiln. After firing most earthenware bodies will be colored white, buff or red, for red earthenware, the firing temperature affects the color of the clay body. Lower temperatures produce a red terracotta color, higher temperatures will make the clay brown or even black. Higher firing temperatures may cause earthenware to bloat, an Introduction to the Technology Of Pottery. Whitewares, Production, Testing And Quality Control, the Potters Dictionary of Materials and Techniques. A & C Black Publishers Limited, London, England, Third Edition,1991
20.
Stoneware
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Earthenware is glazed or unglazed nonvitreous pottery which has normally been fired below 1200°C. Porcelain, bone china and stoneware, all fired at high temperatures to vitrify, are the main other important types of pottery. Pit fired earthenware dates back to as early as 29, 000–25,000 BCE, outside East Asia, porcelain was manufactured only from the 18th century, and then initially as an expensive luxury. Earthenware, when fired, is opaque and non-vitreous, soft, the Combined Nomenclature of the European Communities describes it as being made of selected clays sometimes mixed with feldspars and varying amounts of other minerals and white or light-colored. Generally, earthenware bodies exhibit higher plasticity than most whiteware bodies and hence are easier to shape by RAM press, due to its porosity, earthenware, with a water absorption of 5-8%, must be glazed to be watertight. Earthenware has lower mechanical strength than bone china, porcelain or stoneware, darker-colored terracotta earthenwares, typically orange or red, due to a comparatively high content of iron oxide are widely used for flower pots, tiles and some decorative and oven wares. A general body formulation for contemporary earthenware is 25% kaolin, 25% ball clay, 35% quartz and 15% feldspar. Modern earthenware may be fired to temperatures between 1,000 and 1,150 °C and glost-fired to between 950 to 1,050 °C, the usual practice in factories and some studio potteries. Some studio potters follow the practice, with a low-temperature bisque firing. The firing schedule will be determined by the raw materials used, historically, such high temperatures were unattainable in most cultures and periods until modern times, though Chinese ceramics were far ahead of other cultures in this respect. Earthenware can be produced at firing temperatures as low as 600 °C, much historical pottery was fired somewhere around 800 °C, giving a wide margin of error where there was no precise way of measuring temperature, and very variable conditions within the kiln. After firing most earthenware bodies will be colored white, buff or red, for red earthenware, the firing temperature affects the color of the clay body. Lower temperatures produce a red terracotta color, higher temperatures will make the clay brown or even black. Higher firing temperatures may cause earthenware to bloat, an Introduction to the Technology Of Pottery. Whitewares, Production, Testing And Quality Control, the Potters Dictionary of Materials and Techniques. A & C Black Publishers Limited, London, England, Third Edition,1991
21.
Electron
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The electron is a subatomic particle, symbol e− or β−, with a negative elementary electric charge. Electrons belong to the first generation of the lepton particle family, the electron has a mass that is approximately 1/1836 that of the proton. Quantum mechanical properties of the include a intrinsic angular momentum of a half-integer value, expressed in units of the reduced Planck constant. As it is a fermion, no two electrons can occupy the same state, in accordance with the Pauli exclusion principle. Like all elementary particles, electrons exhibit properties of particles and waves, they can collide with other particles and can be diffracted like light. Since an electron has charge, it has an electric field. Electromagnetic fields produced from other sources will affect the motion of an electron according to the Lorentz force law, electrons radiate or absorb energy in the form of photons when they are accelerated. Laboratory instruments are capable of trapping individual electrons as well as electron plasma by the use of electromagnetic fields, special telescopes can detect electron plasma in outer space. Electrons are involved in applications such as electronics, welding, cathode ray tubes, electron microscopes, radiation therapy, lasers, gaseous ionization detectors. Interactions involving electrons with other particles are of interest in fields such as chemistry. The Coulomb force interaction between the positive protons within atomic nuclei and the negative electrons without, allows the composition of the two known as atoms, ionization or differences in the proportions of negative electrons versus positive nuclei changes the binding energy of an atomic system. The exchange or sharing of the electrons between two or more atoms is the cause of chemical bonding. In 1838, British natural philosopher Richard Laming first hypothesized the concept of a quantity of electric charge to explain the chemical properties of atoms. Irish physicist George Johnstone Stoney named this charge electron in 1891, electrons can also participate in nuclear reactions, such as nucleosynthesis in stars, where they are known as beta particles. Electrons can be created through beta decay of isotopes and in high-energy collisions. The antiparticle of the electron is called the positron, it is identical to the electron except that it carries electrical, when an electron collides with a positron, both particles can be totally annihilated, producing gamma ray photons. The ancient Greeks noticed that amber attracted small objects when rubbed with fur, along with lightning, this phenomenon is one of humanitys earliest recorded experiences with electricity. In his 1600 treatise De Magnete, the English scientist William Gilbert coined the New Latin term electricus, both electric and electricity are derived from the Latin ēlectrum, which came from the Greek word for amber, ἤλεκτρον
22.
Insulator (electricity)
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An electrical insulator is a material whose internal electric charges do not flow freely, very little electric current will flow through it under the influence of an electric field. This contrasts with other materials, semiconductors and conductors, which conduct electric current more easily, the property that distinguishes an insulator is its resistivity, insulators have higher resistivity than semiconductors or conductors. A perfect insulator does not exist, because even insulators contain small numbers of mobile charges which can carry current, in addition, all insulators become electrically conductive when a sufficiently large voltage is applied that the electric field tears electrons away from the atoms. This is known as the voltage of an insulator. Some materials such as glass, paper and Teflon, which have high resistivity, are good electrical insulators. Examples include rubber-like polymers and most plastics which can be thermoset or thermoplastic in nature, insulators are used in electrical equipment to support and separate electrical conductors without allowing current through themselves. An insulating material used in bulk to wrap electrical cables or other equipment is called insulation, the term insulator is also used more specifically to refer to insulating supports used to attach electric power distribution or transmission lines to utility poles and transmission towers. They support the weight of the suspended wires without allowing the current to flow through the tower to ground, electrical insulation is the absence of electrical conduction. Electronic band theory says that a charge flows if states are available into which electrons can be excited and this allows electrons to gain energy and thereby move through a conductor such as a metal. If no such states are available, the material is an insulator, most insulators have a large band gap. This occurs because the valence band containing the highest energy electrons is full, there is always some voltage that gives electrons enough energy to be excited into this band. Once this voltage is exceeded the material ceases being an insulator, however, it is usually accompanied by physical or chemical changes that permanently degrade the materials insulating properties. Materials that lack electron conduction are insulators if they lack other mobile charges as well, for example, if a liquid or gas contains ions, then the ions can be made to flow as an electric current, and the material is a conductor. Electrolytes and plasmas contain ions and act as conductors whether or not electron flow is involved, when subjected to a high enough voltage, insulators suffer from the phenomenon of electrical breakdown. These freed electrons and ions are in turn accelerated and strike other atoms, creating more charge carriers, rapidly the insulator becomes filled with mobile charge carriers, and its resistance drops to a low level. In a solid, the voltage is proportional to the band gap energy. The air in a region around a conductor can break down and ionise without a catastrophic increase in current. Even a vacuum can suffer a sort of breakdown, but in case the breakdown or vacuum arc involves charges ejected from the surface of metal electrodes rather than produced by the vacuum itself
23.
Ceramic engineering
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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, Ceramic materials may have a crystalline or partly crystalline structure, with long-range order on atomic scale. Glass ceramics may have an amorphous or glassy structure, with limited or short-range atomic order, the special character of ceramic materials gives rise to many applications in materials engineering, electrical engineering, chemical engineering and mechanical engineering. As ceramics are heat resistant, they can be used for many tasks for which materials like metal, the word ceramic is derived from the Greek word κεραμικός meaning pottery. It is related to the older Indo-European language root to burn, Ceramic may be used as a noun in the singular to refer to a material or the product of ceramic manufacture. The plural ceramics may be used to refer the making of things out of ceramic materials, Ceramic engineering, like many sciences, evolved from a different discipline by todays standards. Materials science engineering is grouped with ceramics engineering to this day, abraham Darby first used coke in 1709 in Shropshire, England, to improve the yield of a smelting process. Coke is now used to produce carbide ceramics. Potter Josiah Wedgwood opened the first modern factory in Stoke-on-Trent, England. Austrian chemist Carl Josef Bayer, working for the industry in Russia. The Bayer process is used to purify alumina for the ceramic. Brothers Pierre and Jacques Curie discovered piezoelectricity in Rochelle salt circa 1880, piezoelectricity is one of the key properties of electroceramics. Acheson heated a mixture of coke and clay in 1893, and invented carborundum, henri Moissan also synthesized SiC and tungsten carbide in his electric arc furnace in Paris about the same time as Acheson. Karl Schröter used liquid-phase sintering to bond or cement Moissans tungsten carbide particles with cobalt in 1923 in Germany, cemented carbide edges greatly increase the durability of hardened steel cutting tools. W. H. Nernst developed cubic-stabilized zirconia in the 1920s in Berlin and this material is used as an oxygen sensor in exhaust systems. The main limitation on the use of ceramics in engineering is brittleness, the military requirements of World War II encouraged developments, which created a need for high-performance materials and helped speed the development of ceramic science and engineering. Throughout the 1960s and 1970s, new types of ceramics were developed in response to advances in energy, electronics, communications. The discovery of ceramic superconductors in 1986 has spurred intense research to develop superconducting ceramic parts for electronic devices, electric motors, and transportation equipment
24.
Hardness
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Hardness is a measure of how resistant solid matter is to various kinds of permanent shape change when a compressive force is applied. Some materials are harder than others, Hardness is dependent on ductility, elastic stiffness, plasticity, strain, strength, toughness, viscoelasticity, and viscosity. Common examples of matter are ceramics, concrete, certain metals, and superhard materials. There are three types of hardness measurements, scratch, indentation, and rebound. Within each of these classes of measurement there are individual measurement scales, for practical reasons conversion tables are used to convert between one scale and another. Scratch hardness is the measure of how resistant a sample is to fracture or permanent plastic deformation due to friction from a sharp object, the principle is that an object made of a harder material will scratch an object made of a softer material. When testing coatings, scratch hardness refers to the necessary to cut through the film to the substrate. The most common test is Mohs scale, which is used in mineralogy, one tool to make this measurement is the sclerometer. Another tool used to make these tests is the pocket hardness tester and this tool consists of a scale arm with graduated markings attached to a four-wheeled carriage. A scratch tool with a rim is mounted at a predetermined angle to the testing surface. In order to use it a weight of mass is added to the scale arm at one of the graduated markings. The use of the weight and markings allows a known pressure to be applied without the need for complicated machinery. Indentation hardness measures the resistance of a sample to material deformation due to a constant compression load from an object, they are primarily used in engineering. The tests work on the premise of measuring the critical dimensions of an indentation left by a specifically dimensioned and loaded indenter. Common indentation hardness scales are Rockwell, Vickers, Shore, rebound hardness, also known as dynamic hardness, measures the height of the bounce of a diamond-tipped hammer dropped from a fixed height onto a material. This type of hardness is related to elasticity, the device used to take this measurement is known as a scleroscope. Two scales that measures rebound hardness are the Leeb rebound hardness test, there are five hardening processes, Hall-Petch strengthening, work hardening, solid solution strengthening, precipitation hardening, and martensitic transformation. Hardness in the elastic range—a small temporary change in shape for a given force—is known as stiffness in the case of a given object and they exhibit plasticity—the ability to permanently change shape in response to the force, but remain in one piece
25.
Electrical resistivity and conductivity
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Electrical resistivity is an intrinsic property that quantifies how strongly a given material opposes the flow of electric current. A low resistivity indicates a material that allows the flow of electric current. Resistivity is commonly represented by the Greek letter ρ, the SI unit of electrical resistivity is the ohm-metre. Electrical conductivity or specific conductance is the reciprocal of electrical resistivity and it is commonly represented by the Greek letter σ, but κ or γ are also occasionally used. Its SI unit is siemens per metre and CGSE unit is reciprocal second, many resistors and conductors have a uniform cross section with a uniform flow of electric current, and are made of one material. All copper wires, irrespective of their shape and size, have approximately the same resistivity, every material has its own characteristic resistivity – for example, resistivity of rubber is far larger than coppers. If the pipes are the size and shape, the pipe full of sand has higher resistance to flow. Resistance, however, is not solely determined by the presence or absence of sand and it also depends on the length and width of the pipe, short or wide pipes have lower resistance than narrow or long pipes. The above equation can be transposed to get Pouillets law, R = ρ ℓ A, the resistance of a given material increases with length, but decreases with increasing cross-sectional area. From the above equations, resistivity has the SI unit ohm metre, the formula R = ρ ℓ / A can be used to intuitively understand the meaning of a resistivity value. For example, if A = 7000100000000000000♠1 m2 ℓ = 7000100000000000000♠1 m, Conductivity, σ, is defined as the inverse of resistivity, σ =1 ρ. Conductivity has SI units of siemens per metre, the above definition was specific to resistors or conductors with a uniform cross-section, where current flows uniformly through them. A more basic and general definition starts from the fact that a field inside a material makes electric current flow. Conductivity is the inverse, σ =1 ρ = J E, for example, rubber is a material with large ρ and small σ—because even a very large electric field in rubber makes almost no current flow through it. On the other hand, copper is a material with small ρ, according to elementary quantum mechanics, electrons in an atom do not take on arbitrary energy values. Rather, electrons only occupy discrete energy levels in an atom or crystal. When a large number of such allowed energy levels are spaced close together —i. e. have similar energies— we can talk about these energy levels together as an energy band. There can be many such bands in a material, depending on the atomic number
26.
Piezoelectricity
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Piezoelectricity /piˌeɪzoʊˌilɛkˈtrɪsɪti/ is the electric charge that accumulates in certain solid materials in response to applied mechanical stress. The word piezoelectricity means electricity resulting from pressure and it is derived from the Greek piezō or piezein, which means to squeeze or press, and ēlektron, which means amber, an ancient source of electric charge. Piezoelectricity was discovered in 1880 by French physicists Jacques and Pierre Curie, the piezoelectric effect is understood as the linear electromechanical interaction between the mechanical and the electrical state in crystalline materials with no inversion symmetry. The piezoelectric effect is a process in that materials exhibiting the direct piezoelectric effect also exhibit the reverse piezoelectric effect. For example, lead zirconate titanate crystals will generate measurable piezoelectricity when their structure is deformed by about 0. 1% of the original dimension. Conversely, those same crystals will change about 0. 1% of their static dimension when an electric field is applied to the material. The inverse piezoelectric effect is used in the production of sound waves. The pyroelectric effect, by which a material generates a potential in response to a temperature change, was studied by Carl Linnaeus. Drawing on this knowledge, both René Just Haüy and Antoine César Becquerel posited a relationship between stress and electric charge, however, experiments by both proved inconclusive. The first demonstration of the piezoelectric effect was in 1880 by the brothers Pierre Curie. Quartz and Rochelle salt exhibited the most piezoelectricity, the Curies, however, did not predict the converse piezoelectric effect. The converse effect was mathematically deduced from fundamental principles by Gabriel Lippmann in 1881. For the next few decades, piezoelectricity remained something of a laboratory curiosity, more work was done to explore and define the crystal structures that exhibited piezoelectricity. The first practical application for piezoelectric devices was sonar, first developed during World War I, in France in 1917, Paul Langevin and his coworkers developed an ultrasonic submarine detector. The detector consisted of a transducer, made of quartz crystals carefully glued between two steel plates, and a hydrophone to detect the returned echo. The use of piezoelectricity in sonar, and the success of that project, over the next few decades, new piezoelectric materials and new applications for those materials were explored and developed. Piezoelectric devices found homes in many fields, ceramic phonograph cartridges simplified player design, were cheap and accurate, and made record players cheaper to maintain and easier to build. The development of the ultrasonic transducer allowed for easy measurement of viscosity and elasticity in fluids and solids, ultrasonic time-domain reflectometers could find flaws inside cast metal and stone objects, improving structural safety
27.
Glass transition
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An amorphous solid that exhibits a glass transition is called a glass. The reverse transition, achieved by supercooling a viscous liquid into the state, is called vitrification. The glass-transition temperature Tg of a material characterizes the range of temperatures over which this transition occurs. It is always lower than the temperature, Tm, of the crystalline state of the material. Hard plastics like polystyrene and poly are used well below their glass transition temperatures, such conventions include a constant cooling rate and a viscosity threshold of 1012 Pa·s, among others. The question of whether some phase transition underlies the glass transition is a matter of continuing research, the glass transition of a liquid to a solid-like state may occur with either cooling or compression. The transition comprises a smooth increase in the viscosity of a material by as much as 17 orders of magnitude without any pronounced change in material structure, the consequence of this dramatic increase is a glass exhibiting solid-like mechanical properties on the timescale of practical observation. In many materials that undergo a freezing transition, rapid cooling will avoid this phase transition. Other materials, such as polymers, lack a well defined crystalline state and easily form glasses. The tendency for a material to form a glass while quenched is called glass forming ability and this ability depends on the composition of the material and can be predicted by the rigidity theory. Below the transition temperature range, the structure does not relax in accordance with the cooling rate used. The expansion coefficient for the state is roughly equivalent to that of the crystalline solid. If slower cooling rates are used, the time for structural relaxation to occur may result in a higher density glass product. Similarly, by annealing the glass structure in time approaches an equilibrium density corresponding to the liquid at this same temperature. Tg is located at the intersection between the curve for the glassy state and the supercooled liquid. The configuration of the glass in this range changes slowly with time towards the equilibrium structure. The principle of the minimization of the Gibbs free energy provides the driving force necessary for the eventual change. It should be noted here that at higher temperatures than Tg
28.
Superconductivity
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It was discovered by Dutch physicist Heike Kamerlingh Onnes on April 8,1911, in Leiden. Like ferromagnetism and atomic spectral lines, superconductivity is a mechanical phenomenon. It is characterized by the Meissner effect, the ejection of magnetic field lines from the interior of the superconductor as it transitions into the superconducting state. The occurrence of the Meissner effect indicates that superconductivity cannot be simply as the idealization of perfect conductivity in classical physics. The electrical resistance of a metallic conductor decreases gradually as temperature is lowered, in ordinary conductors, such as copper or silver, this decrease is limited by impurities and other defects. Even near absolute zero, a sample of a normal conductor shows some resistance. In a superconductor, the resistance drops abruptly to zero when the material is cooled below its critical temperature, an electric current flowing through a loop of superconducting wire can persist indefinitely with no power source. In 1986, it was discovered that some cuprate-perovskite ceramic materials have a temperature above 90 K. Such a high temperature is theoretically impossible for a conventional superconductor. There are many criteria by which superconductors are classified, by theory of operation, It is conventional if it can be explained by the BCS theory or its derivatives, or unconventional, otherwise. By material, Superconductor material classes include chemical elements, alloys, ceramics, on the other hand, there is a class of properties that are independent of the underlying material. For instance, all superconductors have exactly zero resistivity to low applied currents when there is no magnetic field present or if the field does not exceed a critical value. The resistance of the sample is given by Ohms law as R = V / I, if the voltage is zero, this means that the resistance is zero. Superconductors are also able to maintain a current with no applied voltage whatsoever, experiments have demonstrated that currents in superconducting coils can persist for years without any measurable degradation. Experimental evidence points to a current lifetime of at least 100,000 years, theoretical estimates for the lifetime of a persistent current can exceed the estimated lifetime of the universe, depending on the wire geometry and the temperature. In a normal conductor, an electric current may be visualized as a fluid of electrons moving across an ionic lattice. As a result, the energy carried by the current is constantly being dissipated and this is the phenomenon of electrical resistance and Joule heating. The situation is different in a superconductor, in a conventional superconductor, the electronic fluid cannot be resolved into individual electrons
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Fiberglass
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Fiberglass is a type of fiber-reinforced plastic where the reinforcement fiber is specifically glass fiber. The glass fiber may be arranged, flattened into a sheet. The plastic matrix may be a polymer matrix – most often based on thermosetting polymers such as epoxy, polyester resin. The glass fibers are made of various types of glass depending upon the fiberglass use and these glasses all contain silica or silicate, with varying amounts of oxides of calcium, magnesium, and sometimes boron. To be used in fiberglass, glass fibers have to be made very low levels of defects. Fiberglass is a lightweight material and is used for many products. Although it is not as strong and stiff as composites based on fiber, it is less brittle. Its bulk strength and weight are also better than many metals, other common names for fiberglass are glass-reinforced plastic, glass-fiber reinforced plastic or GFK. Because glass fiber itself is referred to as fiberglass, the composite is also called fiberglass reinforced plastic. This article will adopt the convention that fiberglass refers to the glass fiber reinforced composite material. A patent for this method of producing glass wool was first applied for in 1933, Owens joined with the Corning company in 1935 and the method was adapted by Owens Corning to produce its patented fibreglas in 1936. Originally, fibreglas was a wool with fibers entrapping a great deal of gas, making it useful as an insulator. A suitable resin for combining the fibreglass with a plastic to produce a material was developed in 1936 by du Pont. The first ancestor of modern polyester resins is Cyanamids resin of 1942, peroxide curing systems were used by then. With the combination of fiberglass and resin the gas content of the material was replaced by plastic and this reduced the insulation properties to values typical of the plastic, but now for the first time the composite showed great strength and promise as a structural and building material. Confusingly, many glass fiber composites continued to be called fiberglass, ray Greene of Owens Corning is credited with producing the first composite boat in 1937, but did not proceed further at the time due to the brittle nature of the plastic used. In 1939 Russia was reported to have constructed a boat of plastic materials. The first car to have a body was a 1946 prototype of the Stout Scarab
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Carbon fiber reinforced polymer
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Carbon fiber reinforced polymer, carbon fiber reinforced plastic or carbon fiber reinforced thermoplastic, is an extremely strong and light fiber-reinforced plastic which contains carbon fibers. The spelling fibre is common in British Commonwealth countries, the binding polymer is often a thermoset resin such as epoxy, but other thermoset or thermoplastic polymers, such as polyester, vinyl ester or nylon, are sometimes used. The composite may contain other fibers, such as an aramid, aluminium, ultra-high-molecular-weight polyethylene or glass fibers, the properties of the final CFRP product can also be affected by the type of additives introduced to the binding matrix. The most frequent additive is silica, but other such as rubber. The material is referred to as graphite-reinforced polymer or graphite fiber-reinforced polymer. In product advertisements, it is referred to simply as graphite fiber for short. In this case the composite consists of two parts, a matrix and a reinforcement, in CFRP the reinforcement is carbon fiber, which provides the strength. The matrix is usually a resin, such as epoxy. Because CFRP consists of two elements, the material properties depend on these two elements. The reinforcement will give the CFRP its strength and rigidity, measured by stress, unlike isotropic materials like steel and aluminum, CFRP has directional strength properties. The properties of CFRP depend on the layouts of the carbon fiber, the following equation, E c = V m E m + V f E f is valid for composite materials with the fibers oriented in the direction of the applied load. Typical epoxy-based CFRPs exhibit virtually no plasticity, with less than 0. 5% strain to failure, although CFRPs with epoxy have high strength and elastic modulus, the brittle fracture mechanics present unique challenges to engineers in failure detection since failure occurs catastrophically. As such, recent efforts to toughen CFRPs include modifying the existing epoxy material, One such material with high promise is PEEK, which exhibits an order of magnitude greater toughness with similar elastic modulus and tensile strength. However, PEEK is much more difficult to process and more expensive, despite its high initial strength-to-weight ratio, a design limitation of CFRP is its lack of a definable fatigue endurance limit. This means, theoretically, that stress cycle failure cannot be ruled out, environmental effects such as temperature and humidity can have profound effects on the polymer-based composites, including most CFRPs. While the carbon fibers themselves are not affected by the moisture diffusing into the material, the carbon fibers can cause galvanic corrosion when CRP parts are attached to aluminum. The primary element of CFRP is a filament, this is produced from a precursor polymer such as polyacrylonitrile, rayon. Precursor compositions and mechanical processes used during spinning filament yarns may vary among manufacturers, after drawing or spinning, the polymer filament yarns are then heated to drive off non-carbon atoms, producing the final carbon fiber
31.
Pottery
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Pottery is the craft of making ceramic material into pots or potterywares using mud. Major types of potterywares include earthenware, stoneware and porcelain, the place where such wares are made by a potter is also called a pottery. Early Neolithic pottery have found in places such as Jomon Japan. A clay body can be decorated before or after firing, however, prior to shaping processes. Kneading helps to ensure an even moisture content throughout the body, air trapped within the clay body needs to be removed. This is called de-airing and can be accomplished either by a called a vacuum pug or manually by wedging. Wedging can also produce an even moisture content. Once a clay body has been kneaded and de-aired or wedged, after shaping, it is dried and then fired. Clay ware takes on varying physical characteristics during the making of pottery, at sufficient moisture content, bodies at this stage are in their most plastic form. Leather-hard refers to a body that has been dried partially. At this stage the clay object has approximately 15% moisture content, clay bodies at this stage are very firm and only slightly pliable. Trimming and handle attachment often occurs at the leather-hard state, bone-dry refers to clay bodies when they reach a moisture content at or near 0%. It is now ready to be bisque fired, bisque refers to the clay after the object is shaped to the desired form and fired in the kiln for the first time, known as bisque fired or biscuit fired. This firing changes the body in several ways. Mineral components of the body will undergo chemical changes that will change the colour of the clay. Glaze fired is the stage of some pottery making. A glaze may be applied to the form and the object can be decorated in several ways. After this the object is glazed fired, which causes the material to melt
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Figurine
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A figurine or statuette is a small statue that represents a human, deity or animal, or in practice a pair or small group of them. Figurines have been made in many media, with pottery, metal, wood, glass, ceramic figurines not made of porcelain are called terracottas in historical contexts. Figures with movable parts, allowing limbs to be posed, are likely to be called dolls, mannequins, or action figures, or robots or automata. Figurines and miniatures are used in board games, such as chess. In China, there are extant Neolithic figurines, European prehistoric figurines of women, some appearing pregnant, are called Venus figurines, because of their presumed connection to fertility. The two oldest known examples are made of stone, were found in Africa and Asia, and are several hundred years old. Many made of fired clay have been found in Europe that date to 25-30,000 BC, Olmec figurines in semi-precious stones and pottery had a wide influence all over Mesoamerica about 1000-500 BC, and were apparently usually kept in houses. These early figurines are among the first signs of human culture, one cannot know in some cases how they were used. They probably had religious or ceremonial significance and may have used in many types of rituals. Some may have worn as jewelry or intended to amuse children. Porcelain and other ceramics are common materials for figurines, ancient Greek terracotta figurines, made in moulds, were a large industry by the Hellenistic period, and ones in bronze also very common. In Roman art bronze came to predominate, most of these were religious, and deposited in large numbers in temples as votives, or kept in the home and sometimes buried with their owner. But types such as Tanagra figurines included many purely decorative subjects, there are many early examples from China, which drove the experimentation in Europe to replicate the process. The first European porcelain figurines, produced in a process mastered in Germany were known as Meissen ware after the city where it began, soon the technique was copied in other cities, such as the one depicted from Dresden. Genre figurines of gallant scenes, beggars or figurines of saints are carved from pinewood in Val Gardena, South Tyrol, modern figurines, particularly those made of plastic, are often referred to as figures. They can encompass modern action figures and other figures as well as Precious Moments and Hummel figurines, Bobbleheads, Sebastian Miniatures. Two companies which produce porcelain figurines are Royal Doulton, Lladró, Figurines of comic book or sci-fi/fantasy characters without movable parts have been referred to by the terms inaction figures and staction figures. There is also a known as mini war gaming in which players use figurines in table top based games
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Clay
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Clay is a fine-grained natural rock or soil material that combines one or more clay minerals with traces of metal oxides and organic matter. Geologic clay deposits are composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure. Clays are plastic due to water content and become hard, brittle. Depending on the content in which it is found, clay can appear in various colours from white to dull grey or brown to deep orange-red. Although many naturally occurring deposits include both silts and clay, clays are distinguished from other fine-grained soils by differences in size, silts, which are fine-grained soils that do not include clay minerals, tend to have larger particle sizes than clays. There is, however, some overlap in size and other physical properties. The distinction between silt and clay varies by discipline, geologists and soil scientists usually consider the separation to occur at a particle size of 2 µm, sedimentologists often use 4–5 μm, and colloid chemists use 1 μm. Geotechnical engineers distinguish between silts and clays based on the plasticity properties of the soil, as measured by the soils Atterberg limits, ISO14688 grades clay particles as being smaller than 2 μm and silt particles as being larger. These solvents, usually acidic, migrate through the rock after leaching through upper weathered layers. In addition to the process, some clay minerals are formed through hydrothermal activity. There are two types of deposits, primary and secondary. Primary clays form as residual deposits in soil and remain at the site of formation, secondary clays are clays that have been transported from their original location by water erosion and deposited in a new sedimentary deposit. Clay deposits are associated with very low energy depositional environments such as large lakes. Depending on the source, there are three or four main groups of clays, kaolinite, montmorillonite-smectite, illite, and chlorite. Chlorites are not always considered to be a clay, sometimes being classified as a group within the phyllosilicates. There are approximately 30 different types of clays in these categories. Varve is clay with visible annual layers, which are formed by deposition of those layers and are marked by differences in erosion. This type of deposit is common in glacial lakes
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Sintering
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Sintering is the process of compacting and forming a solid mass of material by heat or pressure without melting it to the point of liquefaction. Sintering happens naturally in mineral deposits or as a process used with metals, ceramics, plastics. The atoms in the materials diffuse across the boundaries of the particles, fusing the particles together, the study of sintering in metallurgy powder-related processes is known as powder metallurgy. An example of sintering can be observed when ice cubes in a glass of water adhere to each other, examples of pressure-driven sintering are the compacting of snowfall to a glacier, or the forming of a hard snowball by pressing loose snow together. The word sinter comes from the Middle High German sinter, a cognate of English cinder, the driving force for densification is the change in free energy from the decrease in surface area and lowering of the surface free energy by the replacement of solid-vapor interfaces. It forms new but lower-energy solid-solid interfaces with a decrease in free energy occurring. On a microscopic scale, material transfer is affected by the change in pressure, If the size of the particle is small, these effects become very large in magnitude. For properties such as strength and conductivity, the area in relation to the particle size is the determining factor. The variables that can be controlled for any material are the temperature. Through time, the radius and the vapor pressure are proportional to 2/3 and to 1/3. The source of power for solid-state processes is the change in free or chemical energy between the neck and the surface of the particle. The pore elimination occurs faster for a trial with many pores of uniform size, for the latter portions of the process, boundary and lattice diffusion from the boundary become important. Sintering is part of the process used in the manufacture of pottery. These objects are made from such as glass, alumina, zirconia, silica, magnesia, lime, beryllium oxide. Some ceramic raw materials have an affinity for water and a lower plasticity index than clay. Sintering is performed at high temperature, besides, second and/or third external force could be used. Commonly used second external force is pressure, so, the sintering that performed just using temperature is generally called pressureless sintering. Pressureless sintering is possible with graded metal-ceramic composites, with a nanoparticle sintering aid, a variant used for 3D shapes is called hot isostatic pressing
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Glazing (ceramics)
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Ceramic glaze is an impervious layer or coating of a vitreous substance which has been fused to a ceramic body through firing. Glaze can serve to color, decorate or waterproof an item, glazing renders earthenware vessels suitable for holding liquids, sealing the inherent porosity of terracotta, the term we now use for basic unglazed earthenware. It also gives a tougher surface, glaze is also used on stoneware and porcelain. In addition to their functionality, glazes can form a variety of finishes, including degrees of glossy or matte finish. Glazes may also enhance the design or texture either unmodified or inscribed, carved or painted. Most pottery produced in recent centuries has been glazed, tiles are almost always glazed, and modern architectural terracotta is very often glazed architectural terra-cotta. Domestic sanitary ware is invariably glazed, as are many used in industry. The most important groups of traditional glazes, named after their main ceramic fluxing agent, are, Lead-glazed earthenware, is shiny and transparent after firing, used for about 2,000 years around the Mediterranean, in Europe and China. Tin-glazed pottery, which coats the ware with a white glaze. Known in the Ancient Near East and then important in Islamic pottery, includes faience, maiolica, majolica and Delftware. Ash glaze, important in East Asia, simply made from wood or plant ash, modern materials technology has invented new vitreous glazes that do not fall into these traditional categories. Glazes need to include a ceramic flux which functions by promoting partial liquefaction in the clay bodies, fluxes lower the high melting point of the glass formers silica, and sometimes boron trioxide. These glass former may be included in the materials, or may be drawn from the clay beneath. Raw materials of ceramic glazes generally include silica, which will be the glass former. Various metal oxides, such as sodium, potassium and calcium, alumina, often derived from clay, stiffens the molten glaze to prevent it from running off the piece. Colorants, such as oxide, copper carbonate or cobalt carbonate. Most commonly, glazes in aqueous suspension of various powdered minerals, other techniques include pouring the glaze over the piece, spraying it onto the piece with an airbrush or similar tool, or applying it directly with a brush or other tool. Small marks left by these spurs are sometimes visible on finished ware, decoration applied under the glaze on pottery is generally referred to as underglaze
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Porosity
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Porosity or void fraction is a measure of the void spaces in a material, and is a fraction of the volume of voids over the total volume, between 0 and 1, or as a percentage between 0 and 100%. Strictly speaking, some measure the accessible void, the total amount of void space accessible from the surface. There are many ways to test porosity in a substance or part, the term porosity is used in multiple fields including pharmaceutics, ceramics, metallurgy, materials, manufacturing, earth sciences, soil mechanics and engineering. Void fraction usually varies from location to location in the flow channel and it fluctuates with time and its value is usually time averaged. In separated flow, it is related to flow rates of the gas and the liquid phase. It is defined by the ratio, ϕ = V V V T where VV is the volume of void-space and VT is the total or bulk volume of material, both the mathematical symbols ϕ and n are used to denote porosity. Porosity is a fraction between 0 and 1, typically ranging from less than 0.01 for solid granite to more than 0.5 for peat and it may also be represented in percent terms by multiplying the fraction by 100. The porosity of a rock, or sedimentary layer, is an important consideration when attempting to evaluate the potential volume of water or hydrocarbons it may contain. Sedimentary porosity is a function of many factors, including but not limited to, rate of burial, depth of burial, the nature of the connate fluids. The principal complication is that there is not a direct proportionality between porosity and hydraulic conductivity but rather an inferred proportionality, there is a clear proportionality between pore throat radii and hydraulic conductivity. Also, there tends to be a proportionality between pore throat radii and pore volume, if the proportionality between pore throat radii and porosity exists then a proportionality between porosity and hydraulic conductivity may exist. Well sorted materials have higher porosity than similarly sized poorly sorted materials, for tables of common porosity values for earth materials, see the further reading section in the Hydrogeology article. Consolidated rocks potentially have more complex dual porosities, as compared with alluvial sediment and this can be split into connected and unconnected porosity. Connected porosity is more easily measured through the volume of gas or liquid that can flow into the rock, porosity is the ratio of pore volume to its total volume. Porosity is controlled by, rock type, pore distribution, cementation, diagenetic history, porosity is not controlled by grain size, as the volume of between-grain space is related only to the method of grain packing. Rocks normally decrease in porosity with age and depth of burial, tertiary age Gulf Coast sandstones are in general more porous than Cambrian age sandstones. There are exceptions to this rule, usually because of the depth of burial and thermal history, porosity of surface soil typically decreases as particle size increases. This is due to soil formation in finer textured surface soils when subject to soil biological processes
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Ceramic art
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Ceramic art is art made from ceramic materials, including clay. It may take forms including art ware, tile, figurines, sculpture, Ceramic art is one of the arts, particularly the visual arts. Of these, it is one of the plastic arts, while some ceramics are considered fine art, some are considered to be decorative, industrial or applied art objects. Ceramics may also be considered artefacts in archaeology, Ceramic art can be made by one person or by a group of people. In a pottery or ceramic factory, a group of people design, manufacture, products from a pottery are sometimes referred to as art pottery. In a one-person pottery studio, ceramists or potters produce studio pottery, the word ceramics comes from the Greek keramikos, meaning pottery, which in turn comes from keramos meaning potters clay. Most traditional ceramic products were made from clay, shaped and subjected to heat, in modern ceramic engineering usage, ceramics is the art and science of making objects from inorganic, non-metallic materials by the action of heat. It excludes glass and mosaic made from glass tesserae, cultures especially noted for ceramics include the Chinese, Cretan, Greek, Persian, Mayan, Japanese, and Korean cultures, as well as the modern Western cultures. Different types of clay, when used with different minerals and firing conditions, are used to produce earthenware, stoneware, porcelain, earthenware is pottery that has not been fired to vitrification and is thus permeable to water. Many types of pottery have been made from it from the earliest times, earthenware is often made from clay, quartz and feldspar. Terracotta, a type of earthenware, is a clay-based unglazed or glazed ceramic and its uses include vessels, water and waste water pipes, bricks, and surface embellishment in building construction. Terracotta has been a medium for ceramic art. Stoneware is a vitreous or semi-vitreous ceramic made primarily from stoneware clay or non-refractory fire clay, stoneware is fired at high temperatures. Vitrified or not, it is nonporous, it may or may not be glazed and it may be vitreous or semi-vitreous. It is usually coloured grey or brownish because of impurities in the used for its manufacture. Porcelain is a material made by heating materials, generally including kaolin, in a kiln to temperatures between 1,200 and 1,400 °C. Porcelain has been described as being completely vitrified, hard, impermeable, white or artificially coloured, translucent and 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 levels of whiteness and translucency
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Ceramic
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A ceramic is an inorganic, non-metallic, solid material comprising metal, non-metal or metalloid atoms primarily held in ionic and covalent bonds. This article gives an overview of ceramic materials from the point of view of materials science, the crystallinity of ceramic materials ranges from highly oriented to semi-crystalline, vitrified, and often completely amorphous. Most often, fired ceramics are either vitrified or semi-vitrified as is the case with earthenware, stoneware, varying crystallinity and electron consumption in the ionic and covalent bonds cause most ceramic materials to be good thermal and electrical insulators. With such a range of possible options for the composition/structure of a ceramic, the breadth of the subject is vast. Many composites, such as fiberglass and carbon fiber, while containing ceramic materials, are not considered to be part of the ceramic family. The earliest ceramics made by humans were pottery objects or figurines made from clay, either by itself or mixed with materials like silica, hardened, sintered. Later ceramics were glazed and fired to create smooth, colored surfaces, decreasing porosity through the use of glassy, ceramics now include domestic, industrial and building products, as well as a wide range of ceramic art. In the 20th century, new materials were developed for use in advanced ceramic engineering. The word ceramic comes from the Greek word κεραμικός, of pottery or for pottery, from κέραμος, potters clay, tile, the earliest known mention of the root ceram- is the Mycenaean Greek ke-ra-me-we, workers of ceramics, written in Linear B syllabic script. The word ceramic may be used as an adjective to describe a material, product or process, or it may be used as a noun, either singular, or, more commonly, as the plural noun ceramics. A ceramic material is an inorganic, non-metallic, often crystalline oxide, nitride or carbide material, some elements, such as carbon or silicon, may be considered ceramics. Ceramic materials are brittle, hard, strong in compression, weak in shearing and they withstand chemical erosion that occurs in other materials subjected to acidic or caustic environments. Ceramics generally can withstand high temperatures, such as temperatures that range from 1,000 °C to 1,600 °C. Glass is often not considered a ceramic because of its amorphous character. However, glassmaking involves several steps of the process and its mechanical properties are similar to ceramic materials. Traditional ceramic raw materials include minerals such as kaolinite, whereas more recent materials include aluminium oxide. The modern ceramic materials, which are classified as advanced ceramics, include silicon 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 used in the medicine, electrical, electronics industries. Crystalline ceramic materials are not amenable to a range of processing
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Semiconductor
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Semiconductors are crystalline or amorphous solids with distinct electrical characteristics. They are of high electrical resistance — higher than typical resistance materials and their resistance decreases as their temperature increases, which is behavior opposite to that of a metal. The behavior of charge carriers which include electrons, ions and electron holes at these junctions is the basis of diodes, transistors and all modern electronics. Semiconductor devices can display a range of properties such as passing current more easily in one direction than the other, showing variable resistance. The modern understanding of the properties of a semiconductor relies on quantum physics to explain the movement of carriers in a crystal lattice. Doping greatly increases the number of carriers within the crystal. When a doped semiconductor contains mostly free holes it is called p-type, the semiconductor materials used in electronic devices are doped under precise conditions to control the concentration and regions of p- and n-type dopants. A single semiconductor crystal can have many p- and n-type regions, although some pure elements and many compounds display semiconductor properties, silicon, germanium, and compounds of gallium are the most widely used in electronic devices. Elements near the so-called metalloid staircase, where the metalloids are located on the table, are usually used as semiconductors. Some of the properties of materials were observed throughout the mid 19th. The first practical application of semiconductors in electronics was the 1904 development of the Cats-whisker detector, developments in quantum physics in turn allowed the development of the transistor in 1947 and the integrated circuit in 1958. There are several developed techniques that allow semiconducting materials to behave like conducting materials and these modifications have two outcomes, n-type and p-type. These refer to the excess or shortage of electrons, respectively, an unbalanced number of electrons would cause a current to flow through the material. Heterojunctions Heterojunctions occur when two differently doped semiconducting materials are joined together, for example, a configuration could consist of p-doped and n-doped germanium. This results in an exchange of electrons and holes between the differently doped semiconducting materials, the n-doped germanium would have an excess of electrons, and the p-doped germanium would have an excess of holes. The transfer occurs until equilibrium is reached by a process called recombination, a product of this process is charged ions, which result in an electric field. Excited Electrons A difference in electric potential on a material would cause it to leave thermal equilibrium. This introduces electrons and holes to the system, which interact via a process called ambipolar diffusion, whenever thermal equilibrium is disturbed in a semiconducting material, the amount of holes and electrons changes
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Greek language
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Greek is an independent branch of the Indo-European family of languages, native to Greece and other parts of the Eastern Mediterranean. It has the longest documented history of any living language, spanning 34 centuries of written records and its writing system has been the Greek alphabet for the major part of its history, other systems, such as Linear B and the Cypriot syllabary, were used previously. The alphabet arose from the Phoenician script and was in turn the basis of the Latin, Cyrillic, Armenian, Coptic, Gothic and many other writing systems. Together with the Latin texts and traditions of the Roman world, during antiquity, Greek was a widely spoken lingua franca in the Mediterranean world and many places beyond. It would eventually become the official parlance of the Byzantine Empire, the language is spoken by at least 13.2 million people today in Greece, Cyprus, Italy, Albania, Turkey, and the Greek diaspora. Greek roots are used to coin new words for other languages, Greek. Greek has been spoken in the Balkan peninsula since around the 3rd millennium BC, the earliest written evidence is a Linear B clay tablet found in Messenia that dates to between 1450 and 1350 BC, making Greek the worlds oldest recorded living language. Among the Indo-European languages, its date of earliest written attestation is matched only by the now extinct Anatolian languages, the Greek language is conventionally divided into the following periods, Proto-Greek, the unrecorded but assumed last ancestor of all known varieties of Greek. The unity of Proto-Greek would have ended as Hellenic migrants entered the Greek peninsula sometime in the Neolithic era or the Bronze Age, Mycenaean Greek, the language of the Mycenaean civilisation. It is recorded in the Linear B script on tablets dating from the 15th century BC onwards, Ancient Greek, in its various dialects, the language of the Archaic and Classical periods of the ancient Greek civilisation. It was widely known throughout the Roman Empire, after the Roman conquest of Greece, an unofficial bilingualism of Greek and Latin was established in the city of Rome and Koine Greek became a first or second language in the Roman Empire. The origin of Christianity can also be traced through Koine Greek, Medieval Greek, also known as Byzantine Greek, the continuation of Koine Greek in Byzantine Greece, up to the demise of the Byzantine Empire in the 15th century. Much of the written Greek that was used as the language of the Byzantine Empire was an eclectic middle-ground variety based on the tradition of written Koine. Modern Greek, Stemming from Medieval Greek, Modern Greek usages can be traced in the Byzantine period and it is the language used by the modern Greeks, and, apart from Standard Modern Greek, there are several dialects of it. In the modern era, the Greek language entered a state of diglossia, the historical unity and continuing identity between the various stages of the Greek language is often emphasised. Greek speakers today still tend to regard literary works of ancient Greek as part of their own rather than a foreign language and it is also often stated that the historical changes have been relatively slight compared with some other languages. According to one estimation, Homeric Greek is probably closer to demotic than 12-century Middle English is to modern spoken English, Greek is spoken by about 13 million people, mainly in Greece, Albania and Cyprus, but also worldwide by the large Greek diaspora. Greek is the language of Greece, where it is spoken by almost the entire population
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Mycenaean Greek
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The language is preserved in inscriptions in Linear B, a script first attested on Crete before the 14th century. Most inscriptions are on tablets found in Knossos, in central Crete, as well as in Pylos. Other tablets have found at Mycenae itself, Tiryns and Thebes and at Chania. The language is named after Mycenae, one of the centres of Mycenaean Greece. The tablets long remained undeciphered, and many languages were suggested for them, the texts on the tablets are mostly lists and inventories. No prose narrative survives, much less myth or poetry, still, much may be glimpsed from these records about the people who produced them and about Mycenaean Greece, the period before the so-called Greek Dark Ages. The Mycenaean language is preserved in Linear B writing, which consists of about 200 syllabic signs, since Linear B was derived from Linear A, the script of an undeciphered Minoan language probably unrelated to Greek, it does not reflect fully the phonetics of Mycenaean. In essence, a number of syllabic signs must represent a much greater number of produced syllables. Orthographic simplifications therefore had to be made, There is no disambiguation for the Greek categories of voice and aspiration except the dentals d, t,
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Linear B
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Linear B is a syllabic script that was used for writing Mycenaean Greek, the earliest attested form of Greek. The script predates the Greek alphabet by several centuries, the oldest Mycenaean writing dates to about 1450 BC. It is descended from the older Linear A, an earlier script used for writing the Minoan language, as is the later Cypriot syllabary. Linear B, found mainly in the archives at Knossos, Cydonia, Pylos, Thebes and Mycenae. The succeeding period, known as the Greek Dark Ages, provides no evidence of the use of writing and it is also the only one of the prehistoric Aegean scripts to have been deciphered, by English architect and self-taught linguist Michael Ventris. Linear B consists of around 87 syllabic signs and over 100 ideographic signs and these ideograms or signifying signs symbolize objects or commodities. They have no value and are never used as word signs in writing a sentence. The application of Linear B appears to have been confined to administrative contexts, in all the thousands of clay tablets, a relatively small number of different hands have been detected,45 in Pylos and 66 in Knossos. It is possible that the script was used only by a guild of professional scribes who served the central palaces, once the palaces were destroyed, the script disappeared. Linear B has roughly 200 signs, divided into syllabic signs with phonetic values, the representations and naming of these signs have been standardized by a series of international colloquia starting with the first in Paris in 1956. Colloquia continue, the 13th occurred in 2010 in Paris, many of the signs are identical or similar to those in Linear A, however, Linear A encodes an as-yet unknown language, and it is uncertain whether similar signs had the same phonetic values. The grid developed during decipherment by Michael Ventris and John Chadwick of phonetic values for syllabic signs is shown below, initial consonants are in the leftmost column, vowels are in the top row beneath the title. The transcription of the syllable is listed next to the sign along with Bennetts identifying number for the sign preceded by an asterisk, in cases where the transcription of the sign remains in doubt, Bennetts number serves to identify the sign. The signs on the tablets and sealings often show considerable variation from each other, discovery of the reasons for the variation and possible semantic differences is a topic of ongoing debate in Mycenaean studies. Many of these were identified by the edition and are shown in the special values below. The second edition relates, It may be taken as axiomatic that there are no true homophones, the unconfirmed identifications of *34 and *35 as ai2 and ai3 were removed. Other values remain unknown, mainly because of scarcity of evidence concerning them, note that *34 and *35 are mirror images of each other but whether this graphic relationship indicates a phonetic one remains unconfirmed. In recent times, CIPEM inherited the authority of Bennett
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