1.
Carbon
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Carbon is a chemical element with symbol C and atomic number 6. It is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds, three isotopes occur naturally, 12C and 13C being stable, while 14C is a radioactive isotope, decaying with a half-life of about 5,730 years. Carbon is one of the few elements known since antiquity, Carbon is the 15th most abundant element in the Earths crust, and the fourth most abundant element in the universe by mass after hydrogen, helium, and oxygen. It is the second most abundant element in the body by mass after oxygen. The atoms of carbon can bond together in different ways, termed allotropes of carbon, the best known are graphite, diamond, and amorphous carbon. The physical properties of carbon vary widely with the allotropic form, for example, graphite is opaque and black while diamond is highly transparent. Graphite is soft enough to form a streak on paper, while diamond is the hardest naturally occurring material known, graphite is a good electrical conductor while diamond has a low electrical conductivity. Under normal conditions, diamond, carbon nanotubes, and graphene have the highest thermal conductivities of all known materials, all carbon allotropes are solids under normal conditions, with graphite being the most thermodynamically stable form. They are chemically resistant and require high temperature to react even with oxygen, the most common oxidation state of carbon in inorganic compounds is +4, while +2 is found in carbon monoxide and transition metal carbonyl complexes. The largest sources of carbon are limestones, dolomites and carbon dioxide, but significant quantities occur in organic deposits of coal, peat, oil. For this reason, carbon has often referred to as the king of the elements. The allotropes of carbon graphite, one of the softest known substances, and diamond. It bonds readily with other small atoms including other carbon atoms, Carbon is known to form almost ten million different compounds, a large majority of all chemical compounds. Carbon also has the highest sublimation point of all elements, although thermodynamically prone to oxidation, carbon resists oxidation more effectively than elements such as iron and copper that are weaker reducing agents at room temperature. Carbon is the element, with a ground-state electron configuration of 1s22s22p2. Its first four ionisation energies,1086.5,2352.6,4620.5 and 6222.7 kJ/mol, are higher than those of the heavier group 14 elements. Carbons covalent radii are normally taken as 77.2 pm,66.7 pm and 60.3 pm, although these may vary depending on coordination number, in general, covalent radius decreases with lower coordination number and higher bond order. Carbon compounds form the basis of all life on Earth
2.
Diamond
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Diamond is a metastable allotrope of carbon, where the carbon atoms are arranged in a variation of the face-centered cubic crystal structure called a diamond lattice. Diamond is less stable than graphite, but the rate from diamond to graphite is negligible at standard conditions. Diamond is renowned as a material with superlative physical qualities, most of which originate from the covalent bonding between its atoms. In particular, diamond has the highest hardness and thermal conductivity of any bulk material and those properties determine the major industrial application of diamond in cutting and polishing tools and the scientific applications in diamond knives and diamond anvil cells. Because of its extremely rigid lattice, it can be contaminated by very few types of impurities, such as boron, small amounts of defects or impurities color diamond blue, yellow, brown, green, purple, pink, orange or red. Diamond also has relatively high optical dispersion, most natural diamonds are formed at high temperature and pressure at depths of 140 to 190 kilometers in the Earths mantle. Carbon-containing minerals provide the source, and the growth occurs over periods from 1 billion to 3.3 billion years. Diamonds are brought close to the Earths surface through deep volcanic eruptions by magma, Diamonds can also be produced synthetically in a HPHT method which approximately simulates the conditions in the Earths mantle. An alternative, and completely different growth technique is chemical vapor deposition, several non-diamond materials, which include cubic zirconia and silicon carbide and are often called diamond simulants, resemble diamond in appearance and many properties. Special gemological techniques have developed to distinguish natural diamonds, synthetic diamonds. The word is from the ancient Greek ἀδάμας – adámas unbreakable, the name diamond is derived from the ancient Greek αδάμας, proper, unalterable, unbreakable, untamed, from ἀ-, un- + δαμάω, I overpower, I tame. Diamonds have been known in India for at least 3,000 years, Diamonds have been treasured as gemstones since their use as religious icons in ancient India. Their usage in engraving tools also dates to early human history, later in 1797, the English chemist Smithson Tennant repeated and expanded that experiment. By demonstrating that burning diamond and graphite releases the same amount of gas, the most familiar uses of diamonds today are as gemstones used for adornment, a use which dates back into antiquity, and as industrial abrasives for cutting hard materials. The dispersion of light into spectral colors is the primary gemological characteristic of gem diamonds. In the 20th century, experts in gemology developed methods of grading diamonds, four characteristics, known informally as the four Cs, are now commonly used as the basic descriptors of diamonds, these are carat, cut, color, and clarity. A large, flawless diamond is known as a paragon and these conditions are met in two places on Earth, in the lithospheric mantle below relatively stable continental plates, and at the site of a meteorite strike. The conditions for diamond formation to happen in the mantle occur at considerable depth corresponding to the requirements of temperature and pressure
3.
Graphite
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Graphite, archaically referred to as plumbago, is a crystalline form of carbon, a semimetal, a native element mineral, and one of the allotropes of carbon. Graphite is the most stable form of carbon under standard conditions, therefore, it is used in thermochemistry as the standard state for defining the heat of formation of carbon compounds. Highly ordered pyrolytic graphite or more correctly highly oriented pyrolytic graphite refers to graphite with a spread between the graphite sheets of less than 1°. The name graphite fiber is sometimes used to refer to carbon fibers or carbon fiber-reinforced polymer. Graphite occurs in rocks as a result of the reduction of sedimentary carbon compounds during metamorphism. It also occurs in rocks and in meteorites. Minerals associated with graphite include quartz, calcite, micas and tourmaline, in meteorites it occurs with troilite and silicate minerals. Small graphitic crystals in meteoritic iron are called cliftonite, Graphite is not mined in the United States, but U. S. production of synthetic graphite in 2010 was 134 kt valued at $1.07 billion. Graphite has a layered, planar structure, the individual layers are called graphene. In each layer, the atoms are arranged in a honeycomb lattice with separation of 0.142 nm. Atoms in the plane are bonded covalently, with three of the four potential bonding sites satisfied. The fourth electron is free to migrate in the plane, making graphite electrically conductive, however, it does not conduct in a direction at right angles to the plane. Bonding between layers is via weak van der Waals bonds, which allows layers of graphite to be easily separated, the two known forms of graphite, alpha and beta, have very similar physical properties, except for that the graphene layers stack slightly differently. The alpha graphite may be flat or buckled. The alpha form can be converted to the form through mechanical treatment. The acoustic and thermal properties of graphite are highly anisotropic, since phonons propagate quickly along the tightly-bound planes, graphites high thermal stability and electrical and thermal conductivity facilitate its widespread use as electrodes and refractories in high temperature material processing applications. However, in oxygen containing atmospheres graphite readily oxidizes to form CO2 at temperatures of 700 °C, Graphite is an electric conductor, consequently, useful in such applications as arc lamp electrodes. It can conduct electricity due to the vast electron delocalization within the carbon layers and these valence electrons are free to move, so are able to conduct electricity
4.
Lonsdaleite
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Lonsdaleite, also called hexagonal diamond in reference to the crystal structure, is an allotrope of carbon with a hexagonal lattice. In nature, it forms when meteorites containing graphite strike the Earth, the great heat and stress of the impact transforms the graphite into diamond, but retains graphites hexagonal crystal lattice. Lonsdaleite was first identified in 1967 from the Canyon Diablo meteorite, hexagonal diamond has also been synthesized in the laboratory by compressing and heating graphite either in a static press or using explosives. It has also produced by chemical vapor deposition, and also by the thermal decomposition of a polymer, poly, at atmospheric pressure, under argon atmosphere. It is translucent, brownish-yellow, and has an index of refraction of 2.40 to 2.41 and its hardness is theoretically superior to that of cubic diamond according to computational simulations but natural specimens exhibited somewhat lower hardness through a large range of values. The cause is speculated as being due to the samples having been riddled with lattice defects, a quantitative analysis of the X-ray diffraction data of lonsdaleite has shown that about equal amounts of hexagonal and cubic stacking sequences are present. Consequently, it has suggested that stacking disordered diamond is the most accurate structural description of lonsdaleite. According to the picture, Lonsdaleite has a hexagonal unit cell, related to the diamond unit cell in the same way that the hexagonal. The diamond structure can be considered to be made up of interlocking rings of six carbon atoms, in lonsdaleite, some rings are in the boat conformation instead. Lonsdaleite is simulated to be 58% harder than diamond on the face and to resist indentation pressures of 152 GPa. This is yet exceeded by IIa diamonds <111> tip hardness of 162 GPa, Lonsdaleite occurs as microscopic crystals associated with diamond in several meteorites, Canyon Diablo, Kenna, and Allan Hills 77283. It is also occurring in non-bolide diamond placer deposits in the Sakha Republic. Its presence in local deposits is claimed as evidence for the Tunguska event being caused by a meteor rather than by a cometary fragment. Aggregated diamond nanorod Glossary of meteoritics List of minerals List of minerals named after people Anthony, materials Science and Technology Division, Naval Research Laboratory website accessed 14 May 2006. Diamond no longer natures hardest material lonsdaleite 3D animation
5.
Buckminsterfullerene
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Buckminsterfullerene is a spherical fullerene molecule with the formula C60. It was first generated in 1985 by Harold Kroto, James R. Heath, Sean OBrien, Robert Curl, Kroto, Curl and Smalley were awarded the 1996 Nobel Prize in Chemistry for their roles in the discovery of buckminsterfullerene and the related class of molecules, the fullerenes. The name is a reference to Buckminster Fuller, as C60 resembles his trademark geodesic domes, Buckminsterfullerene is the most common naturally occurring fullerene molecule, as it can be found in small quantities in soot. Solid and gaseous forms of the molecule have been detected in deep space, Buckminsterfullerene is one of the largest objects to have been shown to exhibit wave–particle duality, as stated in the theory every object exhibits this behavior. Its discovery led to the exploration of a new field of chemistry, Buckminsterfullerene derives from the name of the noted futurist and inventor Buckminster Fuller. One of his designs of a dome structure bears great resemblance to C60, as a result. The general public, however, sometimes refers to buckminsterfullerene, and even Fullers dome structure, the structure associated with fullerenes was described by Leonardo da Vinci. Albrecht Dürer also reproduced a similar icosahedron containing 12 pentagonal and 20 hexagonal faces, theoretical predictions of buckyball molecules appeared in the late 1960s – early 1970s, but they went largely unnoticed. In the early 1970s, the chemistry of unsaturated carbon configurations was studied by a group at the University of Sussex, led by Harry Kroto, in the 1980s a technique was developed by Richard Smalley and Robert Curl at Rice University, Texas to isolate these substances. They used laser vaporization of a target to produce clusters of atoms. Kroto realized that by using a target, any carbon chains formed could be studied. Another interesting fact is that, at the time, astrophysicists were working along with spectroscopists to study infrared emissions from giant red carbon stars. Smalley and team were able to use a laser vaporization technique to create carbon clusters which could potentially emit infrared at the wavelength as had been emitted by the red carbon star. Hence, the inspiration came to Smalley and team to use the technique on graphite to create the first fullerene molecule. C60 was discovered in 1985 by Robert Curl, Harold Kroto, using laser evaporation of graphite they found Cn clusters of which the most common were C60 and C70. A solid rotating graphite disk was used as the surface from which carbon was vaporized using a laser beam creating hot plasma that was passed through a stream of high-density helium gas. The carbon species were subsequently cooled and ionized resulting in the formation of clusters, clusters ranged in molecular masses but Kroto and Smalley found predominance in a C60 cluster that could be enhanced further by letting the plasma react longer. They also discovered that the C60 molecule formed a cage-like structure, for this discovery they were awarded the 1996 Nobel Prize in Chemistry
6.
Fullerene
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A fullerene is a molecule of carbon in the form of a hollow sphere, ellipsoid, tube, and many other shapes. Spherical fullerenes, also referred to as Buckminsterfullerenes, resemble the balls used in football, cylindrical fullerenes are also called carbon nanotubes. Fullerenes are similar in structure to graphite, which is composed of stacked sheets of linked hexagonal rings. The name was an homage to Buckminster Fuller, whose geodesic domes it resembles, the structure was also identified some five years earlier by Sumio Iijima, from an electron microscope image, where it formed the core of a bucky onion. Fullerenes have since found to occur in nature. More recently, fullerenes have been detected in outer space, according to astronomer Letizia Stanghellini, It’s possible that buckyballs from outer space provided seeds for life on Earth. The discovery of fullerenes greatly expanded the number of carbon allotropes, which until recently were limited to graphite, graphene, diamond. The icosahedral C60H60 cage was mentioned in 1965 as a topological structure. Eiji Osawa of Toyohashi University of Technology predicted the existence of C60 in 1970 and he noticed that the structure of a corannulene molecule was a subset of an Association football shape, and he hypothesised that a full ball shape could also exist. Japanese scientific journals reported his idea, but neither it nor any translations of it reached Europe or the Americas, also in 1970, R. W. Henson proposed the structure and made a model of C60. Unfortunately, the evidence for new form of carbon was very weak and was not accepted. The results were never published but were acknowledged in Carbon in 1999, in 1973 independently from Henson, a group of scientists from the USSR, directed by Prof. Bochvar, made a quantum-chemical analysis of the stability of C60 and calculated its electronic structure. As in the cases, the scientific community did not accept the theoretical prediction. The paper was published in 1973 in Proceedings of the USSR Academy of Sciences, in mass spectrometry discrete peaks appeared corresponding to molecules with the exact mass of sixty or seventy or more carbon atoms. Kroto, Curl, and Smalley were awarded the 1996 Nobel Prize in Chemistry for their roles in the discovery of this class of molecules, C60 and other fullerenes were later noticed occurring outside the laboratory. By 1990 it was easy to produce gram-sized samples of fullerene powder using the techniques of Donald Huffman, Wolfgang Krätschmer, Lowell D. Lamb. Fullerene purification remains a challenge to chemists and to a large extent determines fullerene prices, so-called endohedral fullerenes have ions or small molecules incorporated inside the cage atoms. Fullerene is a reactant in many organic reactions such as the Bingel reaction discovered in 1993
7.
C70 fullerene
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C70 fullerene is the fullerene molecule consisting of 70 carbon atoms. It is a cage-like fused-ring structure which resembles a ball, made of 25 hexagons and 12 pentagons, with a carbon atom at the vertices of each polygon. A related fullerene molecule, named buckminsterfullerene, consists of 60 carbon atoms and it was first intentionally prepared in 1985 by Harold Kroto, James R. Heath, Sean OBrien, Robert Curl and Richard Smalley at Rice University. Kroto, Curl and Smalley were awarded the 1996 Nobel Prize in Chemistry for their roles in the discovery of cage-like fullerenes, the name is a homage to Buckminster Fuller, whose geodesic domes these molecules resemble. Theoretical predictions of buckyball molecules appeared in the late 1960s – early 1970s, in the early 1970s, the chemistry of unsaturated carbon configurations was studied by a group at the University of Sussex, led by Harry Kroto and David Walton. In the 1980s a technique was developed by Richard Smalley and Bob Curl at Rice University and they used laser vaporization of a suitable target to produce clusters of atoms. Kroto realized that by using a graphite target, C70 was discovered in 1985 by Robert Curl, Harold Kroto and Richard Smalley. Using laser evaporation of graphite they found Cn clusters of which the most common were C60, for this discovery they were awarded the 1996 Nobel Prize in Chemistry. The discovery of buckyballs was serendipitous, as the scientists were aiming to produce carbon plasmas to replicate, mass spectrometry analysis of the product indicated the formation of spheroidal carbon molecules. In 1990, K. Fostiropoulos, W. Krätchmer and D. R. Huffman developed a simple and efficient method of producing fullerenes in gram and even kilogram amounts which boosted fullerene research. In this technique, carbon soot is produced from two high-purity graphite electrodes by igniting an arc discharge between them in an inert atmosphere, alternatively, soot is produced by laser ablation of graphite or pyrolysis of aromatic hydrocarbons. Fullerenes are extracted from the using a multistep procedure. First, the soot is dissolved in organic solvents. This step yields a solution containing up to 70% of C60 and 15% of C70 and these fractions are separated using chromatography. The C70 molecule has a D5h symmetry and contains 37 faces with an atom at the vertices of each polygon. Its structure is similar to that of C60 molecule, but has a belt of 5 hexagons inserted at the equator, the molecule has eight bond lengths ranging between 0.137 and 0.146 nm. Each carbon atom in the structure is bonded covalently with 3 others, C70 can undergo six reversible, one-electron reductions to C6−70, whereas oxidation is irreversible. The first reduction requires ~1.0 V, indicating that C70 is an electron acceptor, Fullerenes are sparingly soluble in many aromatic solvents such as toluene and others like carbon disulfide, but not in water
8.
Carbon nanotube
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Carbon nanotubes are allotropes of carbon with a cylindrical nanostructure. These cylindrical carbon molecules have unusual properties, which are valuable for nanotechnology, electronics, optics and other fields of materials science and technology. Owing to the exceptional strength and stiffness, nanotubes have been constructed with length-to-diameter ratio of up to 132,000,000,1. In addition, owing to their thermal conductivity, mechanical. For instance, nanotubes form a portion of the material in some baseball bats, golf clubs. Nanotubes are members of the fullerene structural family and their name is derived from their long, hollow structure with the walls formed by one-atom-thick sheets of carbon, called graphene. Nanotubes are categorized as single-walled nanotubes and multi-walled nanotubes, individual nanotubes naturally align themselves into ropes held together by van der Waals forces, more specifically, pi-stacking. Applied quantum chemistry, specifically, orbital hybridization best describes chemical bonding in nanotubes, the chemical bonding of nanotubes is composed entirely of sp2 bonds, similar to those of graphite. These bonds, which are stronger than the sp3 bonds found in alkanes and diamond, most single-walled nanotubes have a diameter of close to 1 nanometer, and can be many millions of times longer. The structure of a SWNT can be conceptualized by wrapping a one-atom-thick layer of graphite called graphene into a seamless cylinder, the way the graphene sheet is wrapped is represented by a pair of indices. The integers n and m denote the number of unit vectors along two directions in the crystal lattice of graphene. If m =0, the nanotubes are called zigzag nanotubes, and if n = m, the diameter of an ideal nanotube can be calculated from its indices as follows d = a π =78.3 p m, where a =0.246 nm. SWNTs are an important variety of carbon nanotube because most of their properties change significantly with the values, in particular, their band gap can vary from zero to about 2 eV and their electrical conductivity can show metallic or semiconducting behavior. Single-walled nanotubes are likely candidates for miniaturizing electronics, the most basic building block of these systems is the electric wire, and SWNTs with diameters of an order of a nanometer can be excellent conductors. One useful application of SWNTs is in the development of the first intermolecular field-effect transistors, the first intermolecular logic gate using SWCNT FETs was made in 2001. A logic gate requires both a p-FET and an n-FET, because SWNTs are p-FETs when exposed to oxygen and n-FETs otherwise, it is possible to expose half of an SWNT to oxygen and protect the other half from it. The resulting SWNT acts as a not logic gate with both p and n-type FETs in the same molecule, prices for single-walled nanotubes declined from around $1500 per gram as of 2000 to retail prices of around $50 per gram of as-produced 40–60% by weight SWNTs as of March 2010. As of 2016 the retail price of as-produced 75% by weight SWNTs were $2 per gram, SWNTs are forecast to make a large impact in electronics applications by 2020 according to the The Global Market for Carbon Nanotubes report
9.
Allotropy
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Allotropy or allotropism is the property of some chemical elements to exist in two or more different forms, in the same physical state, known as allotropes of these elements. Allotropes are different structural modifications of an element, the atoms of the element are bonded together in a different manner, for example, the allotropes of carbon include diamond, graphite, graphene, and fullerenes. The term allotropy is used for only, not for compounds. The more general term, used for any material, is polymorphism. Allotropy refers only to different forms of an element within the same phase, for some elements, allotropes have different molecular formulae which can persist in different phases – for example, two allotropes of oxygen, can both exist in the solid, liquid and gaseous states. The concepts of allotropy was originally proposed in 1841 by the Swedish scientist Baron Jöns Jakob Berzelius, the term is derived from Greek άλλοτροπἱα, meaning variability, changeableness. After the acceptance of Avogadros hypothesis in 1860 it was understood that elements could exist as molecules. In the early 20th century it was recognized that other such as carbon were due to differences in crystal structure. Although many other chemists have repeated this advice, IUPAC and most chemistry texts still favour the usage of allotrope, allotropes are different structural forms of the same element and can exhibit quite different physical properties and chemical behaviours. The change between allotropic forms is triggered by the forces that affect other structures, i. e. pressure, light. Therefore, the stability of the particular allotropes depends on particular conditions.2 °C, as an example of allotropes having different chemical behaviour, ozone is a much stronger oxidizing agent than dioxygen. Typically, elements capable of variable coordination number and/or oxidation states tend to exhibit greater numbers of allotropic forms, another contributing factor is the ability of an element to catenate. Cerium, samarium, dysprosium and ytterbium have three allotropes, praseodymium, neodymium, gadolinium and terbium have two allotropes. Plutonium has six distinct solid allotropes under normal pressures and their densities vary within a ratio of some 4,3, which vastly complicates all kinds of work with the metal. A seventh plutonium allotrope exists at high pressures. The transuranium metals Np, Am, and Cm are also allotropic, promethium, americium, berkelium and californium have three allotropes each. Isomer Polymorphism Superdense carbon allotropes Chisholm, Hugh, ed. Allotropy
10.
Valence (chemistry)
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In chemistry, the valence or valency of an element is a measure of its combining power with other atoms when it forms chemical compounds or molecules. The concept of valence was developed in the half of the 19th century and was successful in explaining the molecular structure of inorganic and organic compounds. The combining power or affinity of an atom of an element was determined by the number of atoms that it combined with. In methane, carbon has a valence of 4, in ammonia, nitrogen has a valence of 3, in water, oxygen has a valence of 2, and in hydrogen chloride, chlorine has a valence of 1. Chlorine, as it has a valence of one, can be substituted for hydrogen, so phosphorus has a valence of 5 in phosphorus pentachloride, PCl5. Valence diagrams of a compound represent the connectivity of the elements, examples are, Valence only describes connectivity, it does not describe the geometry of molecular compounds, or what are now known to be ionic compounds or giant covalent structures. A line between atoms does not represent a pair of electrons as it does in Lewis diagrams and this definition differs from the IUPAC definition as an element can be said to have more than one valence. It is in manner, according to Frankland, that their affinities are best satisfied. Following these examples and postulates, Frankland declares how obvious it is that This “combining power” was afterwards called quantivalence or valency. In 1857 August Kekulé proposed fixed valences for many elements, such as 4 for carbon, and used them to propose structural formulas for many organic molecules, which are still accepted today. Most 19th-century chemists defined the valence of an element as the number of its bonds without distinguishing different types of valence or of bond. For main-group elements, in 1904 Richard Abegg considered positive and negative valences, in 1916, Gilbert N. Lewis explained valence and chemical bonding in terms of a tendency of atoms to achieve a stable octet of 8 valence-shell electrons. According to Lewis, covalent bonding leads to octets by the sharing of electrons, the term covalence is attributed to Irving Langmuir, who stated in 1919 that the number of pairs of electrons which any given atom shares with the adjacent atoms is called the covalence of that atom. The prefix co- means together, so that a co-valent bond means that the share a valence. Pauling also considered hypervalent molecules, in which main-group elements have apparent valences greater than the maximal of 4 allowed by the octet rule. Similar calculations on transition-metal molecules show that the role of p orbitals is minor, so that one s, for elements in the main groups of the periodic table, the valence can vary between 1 and 7. Many elements have a common valence related to their position in the periodic table, the Latin/Greek prefixes uni-/mono-, bi-/di-, ter-/tri-, quadri-/tetra- and quinque-/penta- are used to describe ions in the charge states 1,2,3,4,5 respectively. Polyvalence or multivalence refers to species that are not restricted to a number of valence bonds
11.
Graphene
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Graphene is an allotrope of carbon in the form of a two-dimensional, atomic-scale, hexagonal lattice in which one atom forms each vertex. It is the structural element of other allotropes, including graphite, charcoal. It can be considered as a large aromatic molecule, the ultimate case of the family of flat polycyclic aromatic hydrocarbons. It is about 200 times stronger than the strongest steel and it efficiently conducts heat and electricity and is nearly transparent. Graphene shows a large and nonlinear diamagnetism, greater than graphite, scientists have theorized about graphene for years. It has unintentionally been produced in small quantities for centuries, through the use of pencils and it was originally observed in electron microscopes in 1962, but it was studied only while supported on metal surfaces. The material was later rediscovered, isolated, and characterized in 2004 by Andre Geim, research was informed by existing theoretical descriptions of its composition, structure, and properties. This work resulted in the two winning the Nobel Prize in Physics in 2010 for groundbreaking experiments regarding the material graphene. The global market for graphene reached $9 million by 2012 with most sales in the semiconductor, electronics, battery energy, Graphene is a combination of graphite and the suffix -ene, named by Hanns-Peter Boehm, who described single-layer carbon foils in 1962. The term was used in early descriptions of carbon nanotubes, as well as for epitaxial graphene. Graphene can be considered an infinite alternant polycyclic aromatic hydrocarbon, the IUPAC compendium of technology states, previously, descriptions such as graphite layers, carbon layers, or carbon sheets have been used for the term graphene. It is incorrect to use for a single layer a term includes the term graphite. The term graphene should be used only when the reactions, structural relations or other properties of individual layers are discussed and this definition is narrower than the IUPAC definition and refers to cloven, transferred and suspended graphene. Other forms such as graphene grown on various metals, can become free-standing if, for example, in 1859 Benjamin Collins Brodie became aware of the highly lamellar structure of thermally reduced graphite oxide. The structure of graphite was identified in 1916 by the method of powder diffraction. It was studied in detail by Kohlschütter and Haenni in 1918 and its structure was determined from single-crystal diffraction in 1924. The theory of graphene was first explored by Wallace in 1947 as a point for understanding the electronic properties of 3D graphite. The emergent massless Dirac equation was first pointed out by Semenoff, DiVincenzo, Semenoff emphasized the occurrence in a magnetic field of an electronic Landau level precisely at the Dirac point
12.
Carbon nanobud
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In nanotechnology, a carbon nanobud is a material that combines carbon nanotubes and spheroidal fullerenes, both allotropes of carbon, in the same structure, forming buds attached to the tubes. Carbon nanobuds were discovered and synthesized in 2006, in this new material, fullerenes are covalently bonded to the outer sidewalls of the underlying nanotube. Consequently, nanobuds exhibit properties of carbon nanotubes and fullerenes. For instance, the properties and the electrical conductivity of the nanobuds are similar to those of corresponding carbon nanotubes. However, because of the reactivity of the attached fullerene molecules. Owing to the number of highly curved fullerene surfaces acting as electron emission sites on conductive carbon nanotubes. Randomly oriented nanobuds have already been demonstrated to have a low work function for field electron emission. Reported test measurements show field thresholds of about 0.65 V/μm, the electron transport properties of certain nanobud classes have been treated theoretically. The study shows that electrons indeed pass to the neck and bud region of the nanobud system, canatu Oy, a Finnish company, claims the intellectual property rights for nanobud material, its synthesis processes, and several applications. Properties such as chemical reactivity, good dispersion and variable band gap electronic structure suggest wide applicability of nanobuds, as the production processes are scalable, the nanobud applications may have industrial importance. Several theoretical works also mentioned the magnetism in nanobuds, canatu has demonstrated curved and highly foldable touch screens made with nanobuds
13.
Graphene nanoribbons
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Graphene nanoribbons, are strips of graphene with <50 nm width. Graphene ribbons were introduced as a model by Mitsutaka Fujita and coauthors to examine the edge. GNRs can also be produced by unzipping or axially cutting nanotubes, in one such method multi-walled carbon nanotubes were unzipped in solution by action of potassium permanganate and sulfuric acid. In another method GNRs were produced by plasma etching of nanotubes partly embedded in a polymer film, more recently, graphene nanoribbons were grown onto silicon carbide substrates using ion implantation followed by vacuum or laser annealing. The latter technique allows any pattern to be written on SiC substrates with 5 nm precision, GNRs were grown on the edges of three-dimensional structures etched into silicon carbide wafers. The ribbons had perfectly smooth edges, annealed by the fabrication process, electron mobility measurements surpassing one million correspond to a sheet resistance of one ohm per square— two orders of magnitude lower than in two-dimensional graphene. Nanoribbons narrower than 10 nm grown on a germanium wafer act like semiconductors, inside a reaction chamber, using chemical vapor deposition, methane is used to deposit hydrocarbons on the wafer surface, where they react with each other to produce long, smooth-edged ribbons. The ribbons were used to create prototype transistors, at a very slow growth rate, the graphene crystals naturally grow into long nanoribbons on a specific germanium crystal facet. By controlling the rate and growth time, the researchers achieved control over the nanoribbon width. In 2017 dry contact transfer was used to press a fiberglass applicator coated with a powder of atomically precise graphene nanoribbons on a hydrogen-passivated Si surface under vacuum,80 of 115 GNRs visibly obscured the substrate lattice with an average apparent height of 0.30 nm. The GNRs do not align to the Si lattice, indicating a weak coupling, the average bandgap over 21 GNRs was 2.85 eV with a standard deviation of 0.13 eV. The method unintentionally overlapped some nanoribbons, allowing the study of multilayer GNRs, such overlaps could be formed deliberately by manipulation with a scanning tunneling microscope. Covalent bonds between the Si surface and the GNR leads to metallic behavior, the Si surface atoms move outward, and the GNR changes from flat to distorted, with some C atoms moving in toward the Si surface. The electronic states of GNRs largely depend on the edge structures, in zigzag edges each successive edge segment is at the opposite angle to the previous. In armchair edges, each pair of segments is a 120/-120 degree rotation of the prior pair, zigzag edges provide the edge localized state with non-bonding molecular orbitals near the Fermi energy. They are expected to have changes in optical and electronic properties from quantization. Calculations based on tight binding theory predict that zigzag GNRs are always metallic while armchairs can be metallic or semiconducting, depending on their width. However, density functional theory calculations show that armchair nanoribbons are semiconducting with an energy gap scaling with the inverse of the GNR width, experiments verified that energy gaps increase with decreasing GNR width
14.
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
15.
Dispersion (optics)
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In optics, dispersion is the phenomenon in which the phase velocity of a wave depends on its frequency. Media having this property may be termed dispersive media. Sometimes the term chromatic dispersion is used for specificity, the most familiar example of dispersion is probably a rainbow, in which dispersion causes the spatial separation of a white light into components of different wavelengths. Most often, chromatic dispersion refers to material dispersion, that is. However, in a waveguide there is also the phenomenon of waveguide dispersion, more generally, waveguide dispersion can occur for waves propagating through any inhomogeneous structure, whether or not the waves are confined to some region. In a waveguide, both types of dispersion will generally be present, although they are not strictly additive, for example, in fiber optics the material and waveguide dispersion can effectively cancel each other out to produce a zero-dispersion wavelength, important for fast fiber-optic communication. Material dispersion can be a desirable or undesirable effect in optical applications, the dispersion of light by glass prisms is used to construct spectrometers and spectroradiometers. Holographic gratings are used, as they allow more accurate discrimination of wavelengths. However, in lenses, dispersion causes chromatic aberration, an effect that may degrade images in microscopes, telescopes. The phase velocity, v, of a wave in a uniform medium is given by v = c n where c is the speed of light in a vacuum. In general, the index is some function of the frequency f of the light, thus n = n, or alternatively. The wavelength dependence of a refractive index is usually quantified by its Abbe number or its coefficients in an empirical formula such as the Cauchy or Sellmeier equations. In particular, for materials, the susceptibility χ that appears in the Kramers–Kronig relations is the electric susceptibility χe = n2 −1. The most commonly seen consequence of dispersion in optics is the separation of light into a color spectrum by a prism. From Snells law it can be seen that the angle of refraction of light in a prism depends on the index of the prism material. For visible light, refraction indices n of most transparent materials decrease with increasing wavelength λ,1 < n < n < n, or alternatively, in this case, the medium is said to have normal dispersion. Whereas, if the index increases with increasing wavelength, the medium is said to have anomalous dispersion, at the interface of such a material with air or vacuum, Snells law predicts that light incident at an angle θ to the normal will be refracted at an angle arcsin. Thus, blue light, with a refractive index, will be bent more strongly than red light
16.
Mineral
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A mineral is a naturally occurring chemical compound, usually of crystalline form and abiogenic in origin. A mineral has one specific chemical composition, whereas a rock can be an aggregate of different minerals or mineraloids, the study of minerals is called mineralogy. There are over 5,300 known mineral species, over 5,070 of these have been approved by the International Mineralogical Association, the silicate minerals compose over 90% of the Earths crust. The diversity and abundance of species is controlled by the Earths chemistry. Silicon and oxygen constitute approximately 75% of the Earths crust, which translates directly into the predominance of silicate minerals, minerals are distinguished by various chemical and physical properties. Differences in chemical composition and crystal structure distinguish the various species, changes in the temperature, pressure, or bulk composition of a rock mass cause changes in its minerals. Minerals can be described by their various properties, which are related to their chemical structure. Common distinguishing characteristics include crystal structure and habit, hardness, lustre, diaphaneity, colour, streak, tenacity, cleavage, fracture, parting, more specific tests for describing minerals include magnetism, taste or smell, radioactivity and reaction to acid. Minerals are classified by key chemical constituents, the two dominant systems are the Dana classification and the Strunz classification, the silicate class of minerals is subdivided into six subclasses by the degree of polymerization in the chemical structure. All silicate minerals have a unit of a 4− silica tetrahedron—that is, a silicon cation coordinated by four oxygen anions. These tetrahedra can be polymerized to give the subclasses, orthosilicates, disilicates, cyclosilicates, inosilicates, phyllosilicates, other important mineral groups include the native elements, sulfides, oxides, halides, carbonates, sulfates, and phosphates. The first criterion means that a mineral has to form by a natural process, stability at room temperature, in the simplest sense, is synonymous to the mineral being solid. More specifically, a compound has to be stable or metastable at 25 °C, modern advances have included extensive study of liquid crystals, which also extensively involve mineralogy. Minerals are chemical compounds, and as such they can be described by fixed or a variable formula, many mineral groups and species are composed of a solid solution, pure substances are not usually found because of contamination or chemical substitution. Finally, the requirement of an ordered atomic arrangement is usually synonymous with crystallinity, however, crystals are also periodic, an ordered atomic arrangement gives rise to a variety of macroscopic physical properties, such as crystal form, hardness, and cleavage. There have been recent proposals to amend the definition to consider biogenic or amorphous substances as minerals. The formal definition of an approved by the IMA in 1995, A mineral is an element or chemical compound that is normally crystalline. However, if geological processes were involved in the genesis of the compound, Mineral classification schemes and their definitions are evolving to match recent advances in mineral science
17.
Gemology
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Gemology or gemmology is the science dealing with natural and artificial gemstone materials. It is considered a geoscience and a branch of mineralogy, some jewelers are academically trained gemologists and are qualified to identify and evaluate gems. This committee matured into the Gemmological Association of Great Britain, now an educational charity, the first US graduate of Gem-As Diploma Course, in 1929, was Robert Shipley, who later established both the Gemological Institute of America and the American Gem Society. There are now several schools and associations of gemologists and certification programs around the world. It is often difficult to obtain a judgement from a neutral laboratory. Analysis and estimation in the trade usually have to take place on site. Professional gemologists and gemstone buyers use mobile laboratories, which all necessary instruments in a travel case. Such so-called travel labs even have their own current supply, which makes them independent from infrastructure and they are also suitable for gemological expeditions. Gemstones are basically categorized based on their structure, specific gravity, refractive index. The physical property of hardness is defined by the non-linear Mohs scale of mineral hardness, gemologists study these factors while valuing or appraising cut and polished gemstones. The spectroscopic analysis of cut gemstones also allows a gemologist to understand the structure and identify its origin. For example, a ruby from Burma will have internal and optical activity variance from a Thai ruby. When the gemstones are in a state, the gemologist studies the external structure, the host rock and mineral association. Initially, the stone is identified by its color, refractive index, optical character, specific gravity, Gem identification is basically a process of elimination. Gemstones of similar color undergo non-destructive optical testing until there is one possible identity. Any single test is indicative, only, for example, the specific gravity of ruby is 4.00, glass is 3. 15–4.20, and cubic zirconia is 5. 6–5.9. So one can tell the difference between cubic zirconia and the other two, however, there is overlap between ruby and glass. And, as with all naturally occurring materials, no two gems are identical, one test to determine the gems identity is to measure the refraction of light in the gem
18.
Bort
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Bort or boart is a term used in the diamond industry to refer to shards of non-gem-grade/quality diamonds. In the manufacturing and heavy industries, bort is used to describe dark, the lowest grade, crushing bort, is crushed by steel mortars and used to make industrial-grade abrasive grits. Small bort crystals are used in drill bits, the Democratic Republic of the Congo provides 75% of the world supply of crushing bort
19.
Synthetic diamond
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A synthetic diamond is diamond produced in an artificial process, as opposed to natural diamonds, which are created by geological processes. Synthetic diamond is widely known as HPHT diamond or CVD diamond after the two common production methods. While the term synthetic is associated by consumers with imitation products, in the U. S. the Federal Trade Commission has indicated that the alternative terms laboratory-grown, laboratory-created, and -created would more clearly communicate the nature of the stone. Numerous claims of diamond synthesis were documented between 1879 and 1928, most of those attempts were carefully analyzed but none were confirmed, in the 1940s, systematic research began in the United States, Sweden and the Soviet Union to grow diamonds using CVD and HPHT processes. The first reproducible synthesis was reported around 1953 and those two processes still dominate the production of synthetic diamond. A third method, known as detonation synthesis, entered the market in the late 1990s. In this process, nanometer-sized diamond grains are created in a detonation of carbon-containing explosives, a fourth method, treating graphite with high-power ultrasound, has been demonstrated in the laboratory, but currently has no commercial application. Synthetic diamond is used in abrasives, in cutting and polishing tools. Electronic applications of synthetic diamond are being developed, including high-power switches at power stations, high-frequency field-effect transistors, synthetic diamond detectors of ultraviolet light or high-energy particles are used at high-energy research facilities and are available commercially. It is estimated that 98% of industrial grade diamond demand is supplied with synthetic diamonds, both CVD and HPHT diamonds can be cut into gems and various colors can be produced, clear white, yellow, brown, blue, green and orange. After the 1797 discovery that diamond was pure carbon, many attempts were made to convert various forms of carbon into diamond. The earliest successes were reported by James Ballantyne Hannay in 1879 and their method involved heating charcoal at up to 3500 °C with iron inside a carbon crucible in a furnace. Whereas Hannay used a tube, Moissan applied his newly developed electric arc furnace. The molten iron was then cooled by immersion in water. The contraction generated by the cooling supposedly produced the pressure required to transform graphite into diamond. Moissan published his work in a series of articles in the 1890s, Many other scientists tried to replicate his experiments. Sir William Crookes claimed success in 1909, otto Ruff claimed in 1917 to have produced diamonds up to 7 mm in diameter, but later retracted his statement. In 1926, Dr. J Willard Hershey of McPherson College replicated Moissans and Ruffs experiments, producing a synthetic diamond, despite the claims of Moissan, Ruff, and Hershey, other experimenters were unable to reproduce their synthesis
20.
Diamond cutting
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Diamond cutting is the practice of changing a diamond from a rough stone into a faceted gem. Cutting diamond requires specialized knowledge, tools, equipment, and techniques because of its extreme difficulty, the first guild of diamond cutters and polishers was formed in 1375 in Nuremberg, Germany, and led to the development of various types of cut. This has two meanings in relation to diamonds, the first is the shape, square, oval, and so on. The second relates to the quality of cut within the shape. Since diamonds are one of the hardest materials, special diamond-coated surfaces are used to grind the diamond down, Diamond cutting, as well as overall processing, is concentrated in a few cities around the world. The main diamond trading centers are Antwerp, Tel Aviv, and Dubai from where roughs are sent to the processing centers of India. Diamonds are cut and polished in Surat, India and the Chinese cities of Guangzhou, India in recent years has held between 19–31% of the world market in polished diamonds and China has held 17% of the world market share in a recent year. Another important diamond center is New York City, the diamond cutting process includes these steps, planning, cleaving or sawing, bruting, polishing, and final inspection. Diamond manufacturers analyze diamond rough from a perspective, with two objectives steering decisions made about how a faceted diamond will be cut. The first objective is that of return on investment for the piece of diamond rough. The second is how quickly the finished diamond can be sold, scanning devices are used to get a 3-dimensional computer model of the rough stone. Also, inclusions are photographed and placed on the 3D model, the process of maximizing the value of finished diamonds, from a rough diamond into a polished gemstone, is both an art and a science. The choice of cut is influenced by many factors, market factors include the exponential increase in value of diamonds as weight increases, referred to as weight retention, and the popularity of certain shapes amongst consumers. Physical factors include the shape of the rough stone, and location of the inclusions. The weight retention analysis studies the diamond rough to find the best combination of finished stones as it relates to per carat value. The round brilliant cut and square brilliant cuts are preferred when the crystal is an octahedron, oddly shaped crystals, such as macles are more likely to be cut in a fancy cut—that is, a cut other than the round brilliant—which the particular crystal shape lends itself to. Even with modern techniques, the cutting and polishing of a diamond crystal always results in a loss of weight. Sometimes the cutters compromise and accept lesser proportions and symmetry in order to avoid inclusions or to preserve the weight, since the per-carat price of a diamond shifts around key milestones, many one-carat diamonds are the result of compromising Cut quality for Carat weight
21.
Exploration diamond drilling
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Exploration diamond drilling is used in the mining industry to probe the contents of known ore deposits and potential sites. By withdrawing a small core of rock from the orebody, geologists can analyse the core by chemical assay and conduct petrologic. Rodolphe Leschot is often cited as being the inventor of the first core bit, early diamond drilling opened up many new areas for mineral mining, and was related to a boom in mineral exploration in remote locations. Before the invention of the diamond drill, most mineral prospecting was limited to finding outcrops at the surface. In the late 1970s, General Electric pioneered the technology of polycrystalline diamond compacts as a replacement for natural diamonds in drill bits, Exploration diamond drilling differs from other geological drilling in that a solid core is extracted from depth, for examination on the surface. The key technology of the drill is the actual diamond bit itself. It is composed of industrial diamonds set into a metallic matrix. As shown in the figure, the diamonds are scattered throughout the matrix, the bit is mounted onto a drill stem, which is connected to a rotary drill. Water is injected into the pipe, so as to wash out the rock cuttings produced by the bit. An actual diamond bit is an affair, usually designed for a specific rock type. The drill uses a diamond encrusted drill bit to drill through the rock, the drill produces a core which is photographed and split longitudinally. Half of the core is assayed while the other half is permanently stored for future use. Although a larger diameter core is the most preferred it is the most expensive, the most common diameter sizes of core are NQ and CHD76. Early exploration companies tended to choose drilling contractors who typically charge per meter rates and/or day rate depending on difficulty of project, merely advancing the drill by rotary action causes a core to be extracted inside the barrel as shown. However, at a depth of perhaps 300 m, there must be a way to retrieve the core, constantly withdrawing the entire heavy drill pipe is impractical, so methods were developed to pull up the core inside the barrel. Unfortunately, many require a undisturbed core in fractured rock. The photo shows the extraction of a core, using a triple-tube wire-line system and this is very important when exploring fault zones such as the San Andreas Fault. There are five major wire line tube sizes typically used, larger tubes produced larger diameter rock cores and require more drill power to drive them
22.
Drill bit
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Drill bits are cutting tools used to remove material to create holes, almost always of circular cross-section. Drill bits come in sizes and shape and can create different kinds of holes in many different materials. In order to create holes drill bits are attached to a drill, the drill will grasp the upper end of a bit called the shank in the chuck. Drill bits come in sizes, described in the drill bit sizes article. A comprehensive drill bit and tap size chart lists metric and imperial sized drill bits alongside the required screw tap sizes, there are also certain specialized drill bits that can create holes with a non-circular cross-section. While the term drill may refer to either a machine or a drill bit for use in a drilling machine. In this article, for clarity, drill bit or bit is used throughout to refer to a bit for use in a drilling machine, Drill bit geometry has several characteristics, The spiral in the drill bit controls the rate of chip removal. A fast spiral drill bit is used in high feed rate applications under low spindle speeds, the point angle, or the angle formed at the tip of the bit, is determined by the material the bit will be operating in. Harder materials require a larger point angle, and softer materials require a sharper angle, the correct point angle for the hardness of the material influences wandering, chatter, hole shape, and wear rate. The lip angle determines the amount of support provided to the cutting edge, a greater lip angle will cause the bit to cut more aggressively under the same amount of point pressure as a bit with a smaller lip angle. Both conditions can cause binding, wear, and eventual failure of the tool. The proper amount of lip clearance is determined by the point angle, the length of a bit determines how deep a hole can be drilled, and also determines the stiffness of the bit and accuracy of the resultant hole. While longer bits can drill deeper holes, they are flexible meaning that the holes they drill may have an inaccurate location or wander from the intended axis. Twist drill bits are available in lengths, referred to as Stub-length or Screw-Machine-length, the extremely common Jobber-length. Most drill bits for use have straight shanks. For heavy duty drilling in industry, bits with tapered shanks are sometimes used, other types shanks used include hex-shaped, and various proprietary quick release systems. The diameter-to-length ratio of the bit is usually between 1,1 and 1,10. Much higher ratios are possible, but the higher the ratio, the best geometry to use depends upon the properties of the material being drilled
23.
Diamond anvil
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A diamond anvil cell is a high-pressure device used in scientific experiments. It enables the compression of a piece of material to extreme pressures, typically up to around 100–200 gigapascals. The device has been used to recreate the pressure existing deep inside planets to synthesise materials, notable examples include the non-molecular ice X, polymeric nitrogen and metallic phases of xenon and potentially hydrogen. A DAC consists of two opposing diamonds with a sample compressed between the polished culets, Pressure may be monitored using a reference material whose behavior under pressure is known. Common pressure standards include ruby fluorescence, and various structurally simple metals, the pressure-transmitting medium is enclosed by a gasket and the two diamond anvils. The sample can be viewed through the diamonds and illuminated by X-rays, magnetic and microwave fields can be applied externally to the cell allowing nuclear magnetic resonance, electron paramagnetic resonance and other magnetic measurements. Attaching electrodes to the sample allows electrical and magnetoelectrical measurements as well as heating up the sample to a few thousand degrees, much higher temperatures can be achieved with laser-induced heating, and cooling down to millikelvins has been demonstrated. The operation of the diamond anvil cell relies on a principle, p = F A where p is the pressure, F the applied force. Diamond is a hard and virtually incompressible material, thus minimising the deformation. The anvils were made of tungsten carbide and this device could achieve pressure of a few gigapascals, and was used in electrical resistance and compressibility measurements. The first prototypes were limited in their range and there was not a reliable way to calibrate the pressure. Following the Bridgman anvil, the diamond anvil cell became the most versatile pressure generating device that has a characteristic that sets it apart from the other pressure devices. This provided the high pressure pioneers with the capability to directly observe the properties of a material while under pressure. The potential for the diamond cell was realized by Alvin Van Valkenburg while he was preparing a sample for IR spectroscopy and was checking the alignment of the diamond faces. The diamond cell was created at the National Bureau of Standards by Charles E. Weir, Ellis R. Lippincott, within the group each member focused on different applications of the diamond cell. Van focused on making visual observations, Charles on XRD, Ellis on IR Spectroscopy, during the first experiments using diamond anvils, the sample was placed on the flat tip of the diamond, the culet, and pressed between the diamond faces. As the diamond faces were pushed together, the sample would be pressed. Using a microscope to view the sample, it could be seen that a pressure gradient existed across the sample with the outer most portions of the sample acting as a kind of gasket
24.
Bearing (mechanical)
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A bearing is a machine element that constrains relative motion to only the desired motion, and reduces friction between moving parts. Most bearings facilitate the desired motion by minimizing friction, Bearings are classified broadly according to the type of operation, the motions allowed, or to the directions of the loads applied to the parts. Rotary bearings hold rotating components such as shafts or axles within mechanical systems, the simplest form of bearing, the plain bearing, consists of a shaft rotating in a hole. Lubrication is often used to reduce friction, a wide variety of bearing designs exists to allow the demands of the application to be correctly met for maximum efficiency, reliability, durability and performance. The term bearing is derived from the verb to bear, a bearing being an element that allows one part to bear another. The simplest bearings are bearing surfaces, cut or formed into a part, with varying degrees of control over the form, size, roughness, other bearings are separate devices installed into a machine or machine part. The most sophisticated bearings for the most demanding applications are very precise devices, the invention of the rolling bearing, in the form of wooden rollers supporting, or bearing, an object being moved is of great antiquity, and may predate the invention of the wheel. Though it is claimed that the Egyptians used roller bearings in the form of tree trunks under sleds. They are depicted in their own drawings in the tomb of Djehutihotep as moving massive stone blocks on sledges with liquid-lubricated runners which would constitute a plain bearing, there are also Egyptian drawings of bearings used with hand drills. The earliest recovered example of a rolling element bearing is a ball bearing supporting a rotating table from the remains of the Roman Nemi ships in Lake Nemi. The wrecks were dated to 40 BC, leonardo da Vinci incorporated drawings of ball bearings in his design for a helicopter around the year 1500. This is the first recorded use of bearings in an aerospace design, however, Agostino Ramelli is the first to have published sketches of roller and thrust bearings. An issue with ball and roller bearings is that the balls or rollers rub against each other causing additional friction which can be reduced by enclosing the balls or rollers within a cage, the captured, or caged, ball bearing was originally described by Galileo in the 17th century. The first practical caged-roller bearing was invented in the mid-1740s by horologist John Harrison for his H3 marine timekeeper and this uses the bearing for a very limited oscillating motion but Harrison also used a similar bearing in a truly rotary application in a contemporaneous regulator clock. The first modern recorded patent on ball bearings was awarded to Philip Vaughan and his was the first modern ball-bearing design, with the ball running along a groove in the axle assembly. Bearings played a role in the nascent Industrial Revolution, allowing the new industrial machinery to operate efficiently. For example, they saw use for holding wheel and axle to greatly reduce friction over that of dragging an object by making the act over a shorter distance as the wheel turned. The first plain and rolling-element bearings were wood closely followed by bronze, over their history bearings have been made of many materials including ceramic, sapphire, glass, steel, bronze, other metals and plastic which are all used today
25.
Window
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A window is an opening in a wall, door, roof or vehicle that allows the passage of light and, if not closed or sealed, air and sound by using sheet glass. Modern windows are glazed or covered in some other transparent or translucent material. Windows are held in place by frames, many glazed windows may be opened, to allow ventilation, or closed, to exclude inclement weather. Windows often have a latch or similar mechanism to lock the window shut, the Romans were the first known to use glass for windows, a technology likely first produced in Roman Egypt, in Alexandria ca.100 AD. Paper windows were economical and widely used in ancient China, Korea, in England, glass became common in the windows of ordinary homes only in the early 17th century whereas windows made up of panes of flattened animal horn were used as early as the 14th century. In the 19th century American west, greased paper windows came to be used by itinerant groups, modern-style floor-to-ceiling windows became possible only after the industrial plate glass making processes were perfected. The English language-word window originates from the Old Norse vindauga, from vindr – wind and auga – eye, the Danish word is pronounced fairly similarly to window. Window is first recorded in the early 13th century, and originally referred to a hole in a roof. Window replaced the Old English eagþyrl, which literally means eye-hole, many Germanic languages however adopted the Latin word fenestra to describe a window with glass, such as standard Swedish fönster, or German Fenster. The use of window in English is probably because of the Scandinavian influence on the English language by means of loanwords during the Viking Age, in English the word fenester was used as a parallel until the mid-18th century. Fenestration is still used to describe the arrangement of windows within a façade, as well as defenestration, in the 13th century, the earliest windows were unglazed openings cut in a roof to admit light during the day. Later, windows were covered with animal hide, cloth, or wood, shutters that could be opened and closed came next. Over time, windows were built that both protected the inhabitants from the elements and transmitted light, using small pieces of translucent material set in frameworks of wood. In the Far East, paper was used to fill windows, the Romans were the first known to use glass for windows, a technology likely first produced in Roman Egypt. It would be over a millennium before a window glass became transparent enough to see through clearly, over the centuries techniques were developed to shear through one side of a blown glass cylinder and produce thinner rectangular window panes from the same amount of glass material. This gave rise to tall narrow windows, usually separated by a vertical support called a mullion, mullioned glass windows were the windows of choice among European well-to-do, whereas paper windows were economical and widely used in ancient China, Korea and Japan. In England, glass became common in the windows of homes only in the early 17th century whereas windows made up of panes of flattened animal horn were used as early as the 14th century. Modern-style floor-to-ceiling windows became possible only after the plate glass making processes were perfected
26.
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
27.
Integrated circuit
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An integrated circuit or monolithic integrated circuit is a set of electronic circuits on one small flat piece of semiconductor material, normally silicon. The ICs mass production capability, reliability and building-block approach to circuit design ensured the rapid adoption of standardized ICs in place of using discrete transistors. ICs are now used in all electronic equipment and have revolutionized the world of electronics. Computers, mobile phones, and other home appliances are now inextricable parts of the structure of modern societies, made possible by the small size. These advances, roughly following Moores law, allow a computer chip of 2016 to have millions of times the capacity, ICs have two main advantages over discrete circuits, cost and performance. Cost is low because the chips, with all their components, are printed as a unit by photolithography rather than being constructed one transistor at a time, furthermore, packaged ICs use much less material than discrete circuits. Performance is high because the ICs components switch quickly and consume little power because of their small size, the main disadvantage of ICs is the high cost to design them and fabricate the required photomasks. This high initial cost means ICs are only practical when high production volumes are anticipated, Circuits meeting this definition can be constructed using many different technologies, including thin-film transistor, thick film technology, or hybrid integrated circuit. However, in general usage integrated circuit has come to refer to the single-piece circuit construction originally known as a integrated circuit. Jacobi disclosed small and cheap hearing aids as typical industrial applications of his patent, an immediate commercial use of his patent has not been reported. The idea of the circuit was conceived by Geoffrey Dummer. Dummer presented the idea to the public at the Symposium on Progress in Quality Electronic Components in Washington and he gave many symposia publicly to propagate his ideas, and unsuccessfully attempted to build such a circuit in 1956. A precursor idea to the IC was to create small ceramic squares, Components could then be integrated and wired into a bidimensional or tridimensional compact grid. This idea, which seemed very promising in 1957, was proposed to the US Army by Jack Kilby, however, as the project was gaining momentum, Kilby came up with a new, revolutionary design, the IC. In his patent application of 6 February 1959, Kilby described his new device as a body of semiconductor material … wherein all the components of the circuit are completely integrated. The first customer for the new invention was the US Air Force, Kilby won the 2000 Nobel Prize in Physics for his part in the invention of the integrated circuit. His work was named an IEEE Milestone in 2009, half a year after Kilby, Robert Noyce at Fairchild Semiconductor developed his own idea of an integrated circuit that solved many practical problems Kilbys had not. Noyces design was made of silicon, whereas Kilbys chip was made of germanium, Noyce credited Kurt Lehovec of Sprague Electric for the principle of p–n junction isolation, a key concept behind the IC
28.
Heat sink
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In computers, heat sinks are used to cool central processing units or graphics processors. A heat sink is designed to maximize its surface area in contact with the medium surrounding it. Air velocity, choice of material, protrusion design and surface treatment are factors that affect the performance of a heat sink, heat sink attachment methods and thermal interface materials also affect the die temperature of the integrated circuit. Thermal adhesive or thermal grease improve the heat sinks performance by filling air gaps between the sink and the heat spreader on the device. A heat sink is made out of copper and/or aluminium. Copper is used because it has many desirable properties for thermally efficient, first and foremost, copper is an excellent conductor of heat. This means that high thermal conductivity allows heat to pass through it quickly. Aluminum is used in applications where weight is a big concern, a heat sink transfers thermal energy from a higher temperature device to a lower temperature fluid medium. The fluid medium is air, but can also be water. If the fluid medium is water, the sink is frequently called a cold plate. In thermodynamics a heat sink is a reservoir that can absorb an arbitrary amount of heat without significantly changing temperature. Practical heat sinks for electronic devices must have a higher than the surroundings to transfer heat by convection, radiation. The power supplies of electronics are not 100% efficient, so heat is produced that may be detrimental to the function of the device. As such, a sink is included in the design to disperse heat to improve efficient energy use. To understand the principle of a sink, consider Fouriers law of heat conduction. The rate at which heat is transferred by conduction, q k, is proportional to the product of the temperature gradient, Q k = − k A d T d x Consider a heat sink in a duct, where air flows through the duct. It is assumed that the heat sink base is higher in temperature than the air, when compact heat exchangers are calculated, the logarithmic mean air temperature is used. M ˙ is the air flow rate in kg/s
29.
Electronics
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Electronics is the science of controlling electrical energy electrically, in which the electrons have a fundamental role. Commonly, electronic devices contain circuitry consisting primarily or exclusively of active semiconductors supplemented with passive elements, the science of electronics is also considered to be a branch of physics and electrical engineering. The ability of electronic devices to act as switches makes digital information processing possible, until 1950 this field was called radio technology because its principal application was the design and theory of radio transmitters, receivers, and vacuum tubes. Today, most electronic devices use semiconductor components to perform electron control and this article focuses on engineering aspects of electronics. Components are generally intended to be connected together, usually by being soldered to a circuit board. Components may be packaged singly, or in more complex groups as integrated circuits, some common electronic components are capacitors, inductors, resistors, diodes, transistors, etc. Components are often categorized as active or passive, vacuum tubes were among the earliest electronic components. They were almost solely responsible for the revolution of the first half of the Twentieth Century. They took electronics from parlor tricks and gave us radio, television, phonographs, radar, long distance telephony and they played a leading role in the field of microwave and high power transmission as well as television receivers until the middle of the 1980s. Since that time, solid state devices have all but completely taken over, vacuum tubes are still used in some specialist applications such as high power RF amplifiers, cathode ray tubes, specialist audio equipment, guitar amplifiers and some microwave devices. The 608 contained more than 3,000 germanium transistors, thomas J. Watson Jr. ordered all future IBM products to use transistors in their design. From that time on transistors were almost exclusively used for computer logic, circuits and components can be divided into two groups, analog and digital. A particular device may consist of circuitry that has one or the other or a mix of the two types, most analog electronic appliances, such as radio receivers, are constructed from combinations of a few types of basic circuits. Analog circuits use a range of voltage or current as opposed to discrete levels as in digital circuits. The number of different analog circuits so far devised is huge, especially because a circuit can be defined as anything from a single component, analog circuits are sometimes called linear circuits although many non-linear effects are used in analog circuits such as mixers, modulators, etc. Good examples of analog circuits include vacuum tube and transistor amplifiers, one rarely finds modern circuits that are entirely analog. These days analog circuitry may use digital or even microprocessor techniques to improve performance and this type of circuit is usually called mixed signal rather than analog or digital. Sometimes it may be difficult to differentiate between analog and digital circuits as they have elements of both linear and non-linear operation, an example is the comparator which takes in a continuous range of voltage but only outputs one of two levels as in a digital circuit
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Japan
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Japan is a sovereign island nation in Eastern Asia. Located in the Pacific Ocean, it lies off the eastern coast of the Asia Mainland and stretches from the Sea of Okhotsk in the north to the East China Sea, the kanji that make up Japans name mean sun origin. 日 can be read as ni and means sun while 本 can be read as hon, or pon, Japan is often referred to by the famous epithet Land of the Rising Sun in reference to its Japanese name. Japan is an archipelago consisting of about 6,852 islands. The four largest are Honshu, Hokkaido, Kyushu and Shikoku, the country is divided into 47 prefectures in eight regions. Hokkaido being the northernmost prefecture and Okinawa being the southernmost one, the population of 127 million is the worlds tenth largest. Japanese people make up 98. 5% of Japans total population, approximately 9.1 million people live in the city of Tokyo, the capital of Japan. Archaeological research indicates that Japan was inhabited as early as the Upper Paleolithic period, the first written mention of Japan is in Chinese history texts from the 1st century AD. Influence from other regions, mainly China, followed by periods of isolation, from the 12th century until 1868, Japan was ruled by successive feudal military shoguns who ruled in the name of the Emperor. Japan entered into a period of isolation in the early 17th century. The Second Sino-Japanese War of 1937 expanded into part of World War II in 1941, which came to an end in 1945 following the bombings of Hiroshima and Nagasaki. Japan is a member of the UN, the OECD, the G7, the G8, the country has the worlds third-largest economy by nominal GDP and the worlds fourth-largest economy by purchasing power parity. It is also the worlds fourth-largest exporter and fourth-largest importer, although Japan has officially renounced its right to declare war, it maintains a modern military with the worlds eighth-largest military budget, used for self-defense and peacekeeping roles. Japan is a country with a very high standard of living. Its population enjoys the highest life expectancy and the third lowest infant mortality rate in the world, in ancient China, Japan was called Wo 倭. It was mentioned in the third century Chinese historical text Records of the Three Kingdoms in the section for the Wei kingdom, Wa became disliked because it has the connotation of the character 矮, meaning dwarf. The 倭 kanji has been replaced with the homophone Wa, meaning harmony, the Japanese word for Japan is 日本, which is pronounced Nippon or Nihon and literally means the origin of the sun. The earliest record of the name Nihon appears in the Chinese historical records of the Tang dynasty, at the start of the seventh century, a delegation from Japan introduced their country as Nihon
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Europe
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Europe is a continent that comprises the westernmost part of Eurasia. Europe is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, yet the non-oceanic borders of Europe—a concept dating back to classical antiquity—are arbitrary. Europe covers about 10,180,000 square kilometres, or 2% of the Earths surface, politically, Europe is divided into about fifty sovereign states of which the Russian Federation is the largest and most populous, spanning 39% of the continent and comprising 15% of its population. Europe had a population of about 740 million as of 2015. Further from the sea, seasonal differences are more noticeable than close to the coast, Europe, in particular ancient Greece, was the birthplace of Western civilization. The fall of the Western Roman Empire, during the period, marked the end of ancient history. Renaissance humanism, exploration, art, and science led to the modern era, from the Age of Discovery onwards, Europe played a predominant role in global affairs. Between the 16th and 20th centuries, European powers controlled at times the Americas, most of Africa, Oceania. The Industrial Revolution, which began in Great Britain at the end of the 18th century, gave rise to economic, cultural, and social change in Western Europe. During the Cold War, Europe was divided along the Iron Curtain between NATO in the west and the Warsaw Pact in the east, until the revolutions of 1989 and fall of the Berlin Wall. In 1955, the Council of Europe was formed following a speech by Sir Winston Churchill and it includes all states except for Belarus, Kazakhstan and Vatican City. Further European integration by some states led to the formation of the European Union, the EU originated in Western Europe but has been expanding eastward since the fall of the Soviet Union in 1991. The European Anthem is Ode to Joy and states celebrate peace, in classical Greek mythology, Europa is the name of either a Phoenician princess or of a queen of Crete. The name contains the elements εὐρύς, wide, broad and ὤψ eye, broad has been an epithet of Earth herself in the reconstructed Proto-Indo-European religion and the poetry devoted to it. For the second part also the divine attributes of grey-eyed Athena or ox-eyed Hera. The same naming motive according to cartographic convention appears in Greek Ανατολή, Martin Litchfield West stated that phonologically, the match between Europas name and any form of the Semitic word is very poor. Next to these there is also a Proto-Indo-European root *h1regʷos, meaning darkness. Most major world languages use words derived from Eurṓpē or Europa to refer to the continent, in some Turkic languages the originally Persian name Frangistan is used casually in referring to much of Europe, besides official names such as Avrupa or Evropa
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United States
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Forty-eight of the fifty states and the federal district are contiguous and located in North America between Canada and Mexico. The state of Alaska is in the northwest corner of North America, bordered by Canada to the east, the state of Hawaii is an archipelago in the mid-Pacific Ocean. The U. S. territories are scattered about the Pacific Ocean, the geography, climate and wildlife of the country are extremely diverse. At 3.8 million square miles and with over 324 million people, the United States is the worlds third- or fourth-largest country by area, third-largest by land area. It is one of the worlds most ethnically diverse and multicultural nations, paleo-Indians migrated from Asia to the North American mainland at least 15,000 years ago. European colonization began in the 16th century, the United States emerged from 13 British colonies along the East Coast. Numerous disputes between Great Britain and the following the Seven Years War led to the American Revolution. On July 4,1776, during the course of the American Revolutionary War, the war ended in 1783 with recognition of the independence of the United States by Great Britain, representing the first successful war of independence against a European power. The current constitution was adopted in 1788, after the Articles of Confederation, the first ten amendments, collectively named the Bill of Rights, were ratified in 1791 and designed to guarantee many fundamental civil liberties. During the second half of the 19th century, the American Civil War led to the end of slavery in the country. By the end of century, the United States extended into the Pacific Ocean. The Spanish–American War and World War I confirmed the status as a global military power. The end of the Cold War and the dissolution of the Soviet Union in 1991 left the United States as the sole superpower. The U. S. is a member of the United Nations, World Bank, International Monetary Fund, Organization of American States. The United States is a developed country, with the worlds largest economy by nominal GDP. It ranks highly in several measures of performance, including average wage, human development, per capita GDP. While the U. S. economy is considered post-industrial, characterized by the dominance of services and knowledge economy, the United States is a prominent political and cultural force internationally, and a leader in scientific research and technological innovations. In 1507, the German cartographer Martin Waldseemüller produced a map on which he named the lands of the Western Hemisphere America after the Italian explorer and cartographer Amerigo Vespucci
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Tetrahedron
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In geometry, a tetrahedron, also known as a triangular pyramid, is a polyhedron composed of four triangular faces, six straight edges, and four vertex corners. The tetrahedron is the simplest of all the ordinary convex polyhedra, the tetrahedron is the three-dimensional case of the more general concept of a Euclidean simplex. The tetrahedron is one kind of pyramid, which is a polyhedron with a polygon base. In the case of a tetrahedron the base is a triangle, like all convex polyhedra, a tetrahedron can be folded from a single sheet of paper. For any tetrahedron there exists a sphere on which all four vertices lie, a regular tetrahedron is one in which all four faces are equilateral triangles. It is one of the five regular Platonic solids, which have known since antiquity. In a regular tetrahedron, not only are all its faces the same size and shape, regular tetrahedra alone do not tessellate, but if alternated with regular octahedra they form the alternated cubic honeycomb, which is a tessellation. The regular tetrahedron is self-dual, which means that its dual is another regular tetrahedron, the compound figure comprising two such dual tetrahedra form a stellated octahedron or stella octangula. This form has Coxeter diagram and Schläfli symbol h, the tetrahedron in this case has edge length 2√2. Inverting these coordinates generates the dual tetrahedron, and the together form the stellated octahedron. In other words, if C is the centroid of the base and this follows from the fact that the medians of a triangle intersect at its centroid, and this point divides each of them in two segments, one of which is twice as long as the other. The vertices of a cube can be grouped into two groups of four, each forming a regular tetrahedron, the symmetries of a regular tetrahedron correspond to half of those of a cube, those that map the tetrahedra to themselves, and not to each other. The tetrahedron is the only Platonic solid that is not mapped to itself by point inversion, the regular tetrahedron has 24 isometries, forming the symmetry group Td, isomorphic to the symmetric group, S4. The first corresponds to the A2 Coxeter plane, the two skew perpendicular opposite edges of a regular tetrahedron define a set of parallel planes. When one of these intersects the tetrahedron the resulting cross section is a rectangle. When the intersecting plane is one of the edges the rectangle is long. When halfway between the two edges the intersection is a square, the aspect ratio of the rectangle reverses as you pass this halfway point. For the midpoint square intersection the resulting boundary line traverses every face of the tetrahedron similarly, if the tetrahedron is bisected on this plane, both halves become wedges
34.
Cyclohexane
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Cyclohexane is a cycloalkane with the molecular formula C6H12. Cyclohexane is mainly used for the production of adipic acid and caprolactam. Cyclohexane is a colourless, flammable liquid with a distinctive detergent-like odor, on an industrial scale, cyclohexane is produced by hydrogenation of benzene. Producers of cyclohexane accounts for approximately 11. 4% of global demand for benzene, the reaction is highly exothermic, with ΔH =216.37 kJ/mol). Dehydrogenation commenced noticeably above 300 °C, reflecting the favorable entropy for dehydrogenation, unlike benzene, cyclohexane is not easily obtained from natural resources such as coal. For this reason, early investigators synthesized their cyclohexane samples, in 1867 Marcellin Berthelot reduced benzene with hydroiodic acid at elevated temperatures. In 1894 Baeyer synthesized cyclohexane starting with a Dieckmann condensation of pimelic acid followed by multiple reductions, In the same year E. Haworth, perkin Jr. prepared it via a Wurtz reaction of 1, 6-dibromohexane. Cyclohexane is rather unreactive, being a non-polar, hydrophobic hydrocarbon and it reacts with superacids, such as HF + SbF5, which will lead to cracking. Substituted cyclohexanes, however, may be reactive under a variety of conditions, commercially most of cyclohexane produced is converted into cyclohexanone–cyclohexanol mixture by catalytic oxidation. KA oil is used as a raw material for adipic acid. It is used as a solvent in some brands of correction fluid, cyclohexane is sometimes used as an organic solvent. Cyclohexane is also used for calibration of differential scanning calorimetry instruments, cyclohexane vapour is used in vacuum carburizing furnaces, in heat treating equipment manufacture. The 6-vertex edge ring does not conform to the shape of a perfect hexagon, therefore, to reduce torsional strain, cyclohexane adopts a three-dimensional structure known as the chair conformation. There are also two other intermediate conformers, half chair, which is the most unstable conformer, and twist boat and this was first proposed as early as 1890 by Hermann Sachse, but only gained widespread acceptance much later. The new conformation puts the carbons at an angle of 109. 5°, half of the hydrogens are in the plane of the ring while the other half are perpendicular to the plane. This conformation allows for the most stable structure of cyclohexane, another conformation of cyclohexane exists, known as boat conformation, but it interconverts to the slightly more stable chair formation. If cyclohexane is mono-substituted with a substituent, then the substituent will most likely be found attached in an equatorial position. Cyclohexane has the lowest angle and torsional strain of all the cycloalkanes, the high-temperature phase I, stable between 186 K and the melting point 280 K, is a plastic crystal, which means the molecules retain some rotational degree of freedom
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Cyclohexane conformation
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A cyclohexane conformation is any of several three-dimensional shapes that a cyclohexane molecule can assume while maintaining the integrity of its chemical bonds. The internal angles of a regular hexagon are 120°, while the preferred angle between successive bonds in a carbon chain is about 109. 5°, the tetrahedral angle. Therefore, the ring tends to assume certain non-planar conformations. The most important shapes are called chair, half-chair, boat, the molecule can easily switch between these conformations, and only two of them — chair and twist-boat — can be isolated in pure form. In 1890, Hermann Sachse, a 28-year-old assistant in Berlin and he clearly understood that these forms had two positions for the hydrogen atoms, that two chairs would probably interconvert, and even how certain substituents might favor one of the chair forms. Because he expressed all this in language, few chemists of the time understood his arguments. He had several attempts at publishing these ideas, but none succeeded in capturing the imagination of chemists and his death in 1893 at the age of 31 meant his ideas sank into obscurity. Derek Barton and Odd Hassel shared the 1969 Nobel Prize for work on the conformations of cyclohexane, the carbon-carbon bonds along the cyclohexane ring are sp³ hybrid orbitals, which have tetrahedral symmetry. Therefore, the angles between bonds of a tetravalent carbon atom have a preferred value θ ≈109. 5°, the bonds also have a fairly fixed bond length λ. On the other hand, adjacent carbon atoms are free to rotate about the axis of the bond, there are exactly eight warped polygons with six distinguished corners that have all internal angles equal to θ and all sides equal to λ. In theory, a molecule with any of those ring conformations would be free of angle strain, however, due to interactions between the hydrogen atoms, the angles and bond lengths of the actual chair forms are slightly different from the nominal values. For the same reasons, the boat forms have slightly higher energy than the chair forms. Indeed, the forms are unstable, and deform spontaneously to twist-boat conformations that are local minima of the total energy. Each of the stable ring conformations can be transformed into any other without breaking the ring, however, such transformations must go through other states with stressed rings. In particular, they must go through unstable states where four successive carbon atoms lie on the same plane and these shapes are called half-chair conformations. The two chair conformations have the lowest total energy, and are therefore the most stable, and have D3d symmetry. In the basic chair conformation, the carbons C1 through C6 alternate between two planes, one with C1, C3 and C5, the other with C2, C4. The molecule has an axis perpendicular to these two planes, and is congruent to itself after a rotation of 120° about that axis
36.
Molecular geometry
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Molecular geometry is the three-dimensional arrangement of the atoms that constitute a molecule. It determines several properties of a substance including its reactivity, polarity, phase of matter, color, magnetism and biological activity. The angles between bonds that an atom forms depend only weakly on the rest of molecule, i. e. they can be understood as approximately local, the molecular geometry can be determined by various spectroscopic methods and diffraction methods. IR, microwave and Raman spectroscopy can give information about the molecule geometry from the details of the vibrational and rotational absorbance detected by these techniques. X-ray crystallography, neutron diffraction and electron diffraction can give molecular structure for crystalline solids based on the distance between nuclei and concentration of electron density, gas electron diffraction can be used for small molecules in the gas phase. NMR and FRET methods can be used to determine complementary information including relative distances, dihedral angles, angles, molecular geometries are best determined at low temperature because at higher temperatures the molecular structure is averaged over more accessible geometries. Larger molecules often exist in multiple stable geometries that are close in energy on the energy surface. Geometries can also be computed by ab initio quantum chemistry methods to high accuracy, the molecular geometry can be different as a solid, in solution, and as a gas. The position of each atom is determined by the nature of the bonds by which it is connected to its neighboring atoms. Since the motions of the atoms in a molecule are determined by quantum mechanics, the overall quantum mechanical motions translation and rotation hardly change the geometry of the molecule. In addition to translation and rotation, a type of motion is molecular vibration. The molecular vibrations are harmonic, and the atoms oscillate about their equilibrium positions, at higher temperatures the vibrational modes may be thermally excited, but they oscillate still around the recognizable geometry of the molecule. At 298 K, typical values for the Boltzmann factor β are, β =0.089 for ΔE =500 cm−1, β =0.008 for ΔE =1000 cm−1, β = 7×10−4 for ΔE =1500 cm−1. When an excitation energy is 500 cm−1, then about 8.9 percent of the molecules are excited at room temperature. To put this in perspective, the lowest excitation vibrational energy in water is the bending mode, thus, at room temperature less than 0.07 percent of all the molecules of a given amount of water will vibrate faster than at absolute zero. As stated above, rotation hardly influences the molecular geometry, but, as a quantum mechanical motion, it is thermally excited at relatively low temperatures. From a classical point of view it can be stated that at temperatures more molecules will rotate faster. In quantum mechanical language, more eigenstates of higher angular momentum become thermally populated with rising temperatures, typical rotational excitation energies are on the order of a few cm−1
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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
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Abraham Gottlob Werner
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Abraham Gottlob Werner was a German geologist who set out an early theory about the stratification of the Earths crust and propounded a history of the Earth that came to be known as Neptunism. He has been called the father of German geology, Werner was born in Wehrau, a village in Prussian Silesia. His family had been involved in the industry for many years. His father, Abraham David Werner, was a foreman at a foundry in Wehrau, while in Leipzig, Werner became interested in the systematic identification and classification of minerals. Within a year he published the first modern textbook on descriptive mineralogy, robert Jameson who became professor at Edinburgh and Andres Manuel del Rio who discovered vanadium. Socratic in his style, Werner developed an appreciation for the broader implications and interrelations of geology within his students. Werner was plagued by frail health his entire life, and passed a quiet existence in the environs of Freiberg. An avid mineral collector in his youth, he abandoned field work altogether in his later life, there is no evidence that he had ever traveled beyond Saxony in his entire adult life. He died at Dresden from internal complications said to have been caused by his consternation over the misfortunes that had befallen Saxony during the Napoleonic Wars and he was elected a foreign member of the Royal Swedish Academy of Sciences in 1810. Starting from the traditions of stratigraphy and cosmogony in Europe. Transition Series, more indurated limestones, dikes, sills, and these were universal formations extending without interruption around the world. Secondary or Stratified Series, the remaining, obviously stratified fossiliferous rocks and these were thought to represent the emergence of mountains from beneath the ocean and were formed from the resulting products of erosion deposited on their flanks. Alluvial or Tertiary Series, poorly consolidated sands, gravels, volcanic Series, younger lava flows demonstrably associated with volcanic vents. Werner believed that these reflected the local effects of burning coal beds. A universal ocean led directly to the idea of universal formations and he coined the term geognosy to define a science based on the recognition of the order, position, and relation of the layers forming the Earth. Werner believed that geognosy represented fact and not theory and his followers resisted speculation, and as a result Wernerian geognosy and Neptunism became dogma and ceased to contribute to further understanding of the history of the Earth. A principal focus of Neptunism that provoked almost immediate controversy involved the origin of basalt, basalts, particularly formed as sills, were differentiated from surface lava flows, and the two were not recognized as the same rock type by Werner and his students during this period. Lavas and volcanoes of obviously igneous origin were treated as very recent phenomena unrelated to the ocean that formed the layers of the Earth
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Standard enthalpy of formation
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Its symbol is ΔHo f or ΔfHo. The superscript Plimsoll on this symbol indicates that the process has occurred under standard conditions at the specified temperature. One exception is phosphorus, for which the most stable form at 1 atm is black phosphorus and this is true for all enthalpies of formation. In physics the energy per particle is expressed in electronvolts. All elements in their states have a standard enthalpy of formation of zero. The formation reaction is a constant pressure and constant temperature process, since the pressure of the standard formation reaction is fixed at 1 atm, the standard formation enthalpy or reaction heat is a function of temperature. For tabulation purposes, standard formation enthalpies are all given at a temperature,298 K. The standard enthalpy of formation is equivalent to the sum of separate processes included in the Born–Haber cycle of synthesis reactions. This is because enthalpy is a state function, in the example above the standard enthalpy change of formation for sodium chloride is equal to the sum of the standard enthalpy change of formation for each of the steps involved in the process. This is especially useful for very long reactions with many intermediate steps, chemists may use standard enthalpies of formation for a reaction that is hypothetical. That it is shows that the reaction, if it were to proceed, would be exothermic. It is possible to heat of formations for simple unstrained organic compounds with the Heat of formation group additivity method. Standard enthalpies of formation are used in thermochemistry to find the enthalpy change of any reaction. This implies that the reaction is exothermic, the converse is also true, the standard enthalpy of reaction will be positive for an endothermic reaction. When a reaction is reversed, the magnitude of ΔH stays the same, when the balanced equation for a reaction is multiplied by an integer, the corresponding value of ΔH must be multiplied by that integer as well. Allotropes of an element other than the state generally have non-zero standard enthalpies of formation. Standard enthalpy of sublimation, or heat of sublimation, is defined as the required to sublime one mole of the substance under standard conditions. Standard enthalpy of solution is the change associated with the dissolution of a substance in a solvent at constant pressure under standard conditions
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Electrical conductor
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In physics and electrical engineering, a conductor is an object or type of material that allows the flow of an electrical current in one or more directions. Materials made of metal are common electrical conductors, Electrical current is generated by the flow of negatively charged electrons, positively charged holes, and positive or negative ions in some cases. In order for current to flow, it is not necessary for one charged particle to travel from the producing the current to that consuming it. Instead, the particle simply needs to nudge its neighbor a finite amount who will nudge its neighbor and on and on until a particle is nudged into the consumer. Essentially what is occurring here is a chain of momentum transfer between mobile charge carriers, the Drude model of conduction describes this process more rigorously. Insulators are non-conducting materials with few mobile charges that support only insignificant electric currents, the resistance of a given conductor depends on the material it is made of, and on its dimensions. For a given material, the resistance is proportional to the cross-sectional area. For example, a copper wire has lower resistance than an otherwise-identical thin copper wire. Also, for a material, the resistance is proportional to the length, for example. The resistance R and conductance G of a conductor of uniform cross section, therefore, the resistivity and conductivity are proportionality constants, and therefore depend only on the material the wire is made of, not the geometry of the wire. Resistivity and conductivity are reciprocals, ρ =1 / σ, resistivity is a measure of the materials ability to oppose electric current. This formula is not exact, It assumes the current density is uniform in the conductor. However, this still provides a good approximation for long thin conductors such as wires. Another situation this formula is not exact for is with alternating current, then, the geometrical cross-section is different from the effective cross-section in which current actually flows, so the resistance is higher than expected. Similarly, if two conductors are each other carrying AC current, their resistances increase due to the proximity effect. Aside from the geometry of the wire, temperature also has a significant effect on the efficacy of conductors, temperature affects conductors in two main ways, the first is that materials may expand under the application of heat. The amount that the material will expand is governed by the expansion coefficient specific to the material. Such an expansion will change the geometry of the conductor and therefore its characteristic resistance, however, this effect is generally small, on the order of 10−6
41.
Delocalized electron
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In chemistry, delocalized electrons are electrons in a molecule, ion or solid metal that are not associated with a single atom or a covalent bond. The term is general and can have different meanings in different fields. In organic chemistry, this refers to resonance in conjugated systems, in solid-state physics, this refers to free electrons that facilitate electrical conduction. In quantum chemistry, this refers to molecular orbitals that extend over several adjacent atoms, in the simple aromatic ring of benzene the delocalization of six π electrons over the C6 ring is often graphically indicated by a circle. The fact that the six C-C bonds are equidistant is one indication of this delocalization, in valence bond theory, delocalization in benzene is represented by resonance structures. Delocalized electrons also exist in the structure of solid metals, metallic structure consists of aligned positive ions in a sea of delocalized electrons. This means that the electrons are free to move throughout the structure, in diamond all four outer electrons of each carbon atom are localized between the atoms in covalent bonding. The movement of electrons is restricted and diamond does not conduct an electric current, in graphite, each carbon atom uses only 3 of its 4 outer energy level electrons in covalently bonding to three other carbon atoms in a plane. Each carbon atom contributes one electron to a system of electrons that is also a part of the chemical bonding. The delocalized electrons are free to move throughout the plane, for this reason, graphite conducts electricity along the planes of carbon atoms, but does not conduct in a direction at right angles to the plane. Standard ab initio quantum chemistry methods lead to delocalized orbitals that, in general, localized orbitals may then be found as linear combinations of the delocalized orbitals, given by an appropriate unitary transformation. In the methane molecule for example, ab initio calculations show bonding character in four molecular orbitals, there are two orbital levels, a bonding molecular orbital formed from the 2s orbital on carbon and triply degenerate bonding molecular orbitals from each of the 2p orbitals on carbon. The localized sp3 orbitals corresponding to each individual bond in valence bond theory can be obtained from a combination of the four molecular orbitals
42.
Pi bond
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In chemistry, pi bonds are covalent chemical bonds where two lobes of one involved atomic orbital overlap two lobes of the other involved atomic orbital. Each of these orbitals is zero at a shared nodal plane. The same plane is also a plane for the molecular orbital of the pi bond. The Greek letter π in their name refers to p orbitals, P orbitals often engage in this sort of bonding. D orbitals also engage in pi bonding, and form part of the basis for metal-metal multiple bonding, Pi bonds are usually weaker than sigma bonds. From the perspective of quantum mechanics, this weakness is explained by significantly less overlap between the component p-orbitals due to their parallel orientation. This is contrasted by sigma bonds which form bonding orbitals directly between the nuclei of the atoms, resulting in greater overlap and a strong sigma bond. Pi bonds result from overlap of atomic orbitals that are in contact through two areas of overlap, pi-bonds are more diffuse bonds than the sigma bonds. Electrons in pi bonds are referred to as pi electrons. Molecular fragments joined by a pi bond cannot rotate about that bond without breaking the pi bond, for homonuclear diatomic molecules, bonding π molecular orbitals have only the one nodal plane passing through the bonded atoms, and no nodal planes between the bonded atoms. The corresponding antibonding, or π* molecular orbital, is defined by the presence of a nodal plane between these two bonded atoms. A typical double bond consists of one bond and one pi bond, for example. A typical triple bond, for example in acetylene, consists of one sigma bond, two pi bonds are the maximum that can exist between a given pair of atoms. Quadruple bonds are rare and can be formed only between transition metal atoms, and consist of one sigma bond, two pi bonds and one delta bond. A pi bond is weaker than a bond, but the combination of pi. The enhanced strength of a multiple bond versus a single is indicated in many ways, for example, in organic chemistry, carbon–carbon bond lengths are about 154 pm in ethane,134 pm in ethylene and 120 pm in acetylene. More bonds make the total bond shorter and stronger, a pi bond can exist between two atoms that do not have a net sigma-bonding effect between them. In certain metal complexes, pi interactions between an atom and alkyne and alkene pi antibonding orbitals form pi-bonds
43.
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
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Cleavage (crystal)
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Cleavage, in mineralogy, is the tendency of crystalline materials to split along definite crystallographic structural planes. Cleavage forms parallel to planes, Basal or pinacoidal cleavage occurs when there is only one cleavage plane. Mica also has basal cleavage, this is why mica can be peeled into thin sheets, cubic cleavage occurs on when there are three cleavage planes intersecting at 90 degrees. Halite has cubic cleavage, and therefore, when halite crystals are broken, octahedral cleavage occurs when there are four cleavage planes in a crystal. Octahedral cleavage is common for semiconductors, rhombohedral cleavage occurs when there are three cleavage planes intersecting at angles that are not 90 degrees. Prismatic cleavage occurs when there are two planes in a crystal. Dodecahedral cleavage occurs when there are six cleavage planes in a crystal, crystal parting occurs when minerals break along planes of structural weakness due to external stress or along twin composition planes. Parting breaks are very similar in appearance to cleavage, but only due to stress. Examples include magnetite which shows octahedral parting, the parting of corundum. Cleavage is a property traditionally used in mineral identification, both in hand specimen and microscopic examination of rock and mineral studies. As an example, the angles between the cleavage planes for the pyroxenes and the amphiboles are diagnostic. Crystal cleavage is of importance in the electronics industry and in the cutting of gemstones. Precious stones are generally cleaved by impact, as in diamond cutting, synthetic single crystals of semiconductor materials are generally sold as thin wafers which are much easier to cleave. Elemental semiconductors are diamond cubic, a group for which octahedral cleavage is observed. This means that some orientations of wafer allow near-perfect rectangles to be cleaved, most other commercial semiconductors can be made in the related zinc blende structure, with similar cleavage planes. Cleavage Mineral galleries, Mineral properties – Cleavage
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Vacuum
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Vacuum is space void of matter. The word stems from the Latin adjective vacuus for vacant or void, an approximation to such vacuum is a region with a gaseous pressure much less than atmospheric pressure. In engineering and applied physics on the hand, vacuum refers to any space in which the pressure is lower than atmospheric pressure. The Latin term in vacuo is used to describe an object that is surrounded by a vacuum, the quality of a partial vacuum refers to how closely it approaches a perfect vacuum. Other things equal, lower gas pressure means higher-quality vacuum, for example, a typical vacuum cleaner produces enough suction to reduce air pressure by around 20%. Ultra-high vacuum chambers, common in chemistry, physics, and engineering, operate below one trillionth of atmospheric pressure, outer space is an even higher-quality vacuum, with the equivalent of just a few hydrogen atoms per cubic meter on average. In the electromagnetism in the 19th century, vacuum was thought to be filled with a medium called aether, in modern particle physics, the vacuum state is considered the ground state of matter. Vacuum has been a frequent topic of debate since ancient Greek times. Evangelista Torricelli produced the first laboratory vacuum in 1643, and other techniques were developed as a result of his theories of atmospheric pressure. A torricellian vacuum is created by filling a glass container closed at one end with mercury. Vacuum became an industrial tool in the 20th century with the introduction of incandescent light bulbs and vacuum tubes. The recent development of human spaceflight has raised interest in the impact of vacuum on human health, the word vacuum comes from Latin an empty space, void, noun use of neuter of vacuus, meaning empty, related to vacare, meaning be empty. Vacuum is one of the few words in the English language that contains two consecutive letters u. Historically, there has been dispute over whether such a thing as a vacuum can exist. Ancient Greek philosophers debated the existence of a vacuum, or void, in the context of atomism, Aristotle believed that no void could occur naturally, because the denser surrounding material continuum would immediately fill any incipient rarity that might give rise to a void. Almost two thousand years after Plato, René Descartes also proposed a geometrically based alternative theory of atomism, without the problematic nothing–everything dichotomy of void, by the ancient definition however, directional information and magnitude were conceptually distinct. The explanation of a clepsydra or water clock was a topic in the Middle Ages. Although a simple wine skin sufficed to demonstrate a partial vacuum, in principle and he concluded that airs volume can expand to fill available space, and he suggested that the concept of perfect vacuum was incoherent. However, according to Nader El-Bizri, the physicist Ibn al-Haytham and the Mutazili theologians disagreed with Aristotle and Al-Farabi, using geometry, Ibn al-Haytham mathematically demonstrated that place is the imagined three-dimensional void between the inner surfaces of a containing body
. PMID 16432191.