Carbon ?chemical element with symbol C

Carbon is the chemical element with symbol C and atomic number 6. As a member ofgroup 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalentchemical bonds. There are three naturally occurring isotopes, with 12C and 13C being stable, while 14C isradioactive, decaying with a half-life of about 5,730 years.Sony VAIO VGN-SR11M Battery

Carbon is one of the few elements known since antiquity.

There are several allotropes of carbon of which the best known are graphite, diamond, and amorphous carbon.Thephysical properties of carbon vary widely with the allotropic form. For example, diamond is highly transparent, while graphite is opaque and black.Sony VAIO VGN-SR11MR Battery

Diamond is among the hardest materials known, while graphite is soft enough to form a streak on paper (hence its name, from the Greek word "to write"). Diamond has a very low electrical conductivity, while graphite is a very good conductor. Under normal conditions, diamond has the highest thermal conductivity of all known materials.Sony VAIO VGN-SR140D Battery

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 other transition metalcarbonyl complexes. Sony VAIO VGN-SR140D/B Battery

The largest sources of inorganic carbon are limestones, dolomites and carbon dioxide, but significant quantities occur in organic deposits of coal, peat, oil and methane clathrates. Carbon forms morecompounds than any other element, with almost ten million pure organic compounds described to date, which in turn are a tiny fraction of such compounds that are theoretically possible under standard conditions.Sony VAIO VGN-SR140D/P Battery

Carbon is the 15th most abundant element in the Earth's crust, and the fourth most abundant element in the universe by mass after hydrogen, helium, and oxygen. It is present in all known life forms, and in the human body carbon is the second most abundant element by mass (about 18.5%) after oxygen.Sony VAIO VGN-SR140D/S Battery

This abundance, together with the unique diversity of organic compounds and their unusual polymer-forming ability at the temperatures commonly encountered onEarth, make this element the chemical basis of all known life.

Characteristics

The different forms or allotropes of carbon (see below) include the hardest naturally occurring substance, diamond, and also one of the softest known substances, graphite. Sony VAIO VGN-SR140E Battery

Moreover, it has an affinity for bonding with other smallatoms, including other carbon atoms, and is capable of forming multiple stablecovalent bonds with such atoms. As a result, carbon is known to form almost ten million different compounds; the large majority of all chemical compounds. Carbon also has the highest sublimation point of all elements.Sony VAIO VGN-SR140E/B Battery

At atmospheric pressure it has no melting point as its triple point is at 10.8 ± 0.2 MPa and 4,600 ± 300 K (~4,330 °C or 7,820 °F), so it sublimates at about 3,900 K.

Carbon sublimes in a carbon arc which has a temperature of about 5,800 K (5,530 °C; 9,980 °F).Sony VAIO VGN-SR140E/P Battery

Thus, irrespective of its allotropic form, carbon remains solid at higher temperatures than the highest melting point metals such as tungsten or rhenium. 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.Sony VAIO VGN-SR140E/S Battery

Carbon compounds form the basis of all known life on Earth, and the carbon-nitrogen cycle provides some of the energy produced by the Sun and other stars. Although it forms an extraordinary variety of compounds, most forms of carbon are comparatively unreactive under normal conditions. At standard temperature and pressure, it resists all but the strongest oxidizers. Sony VAIO VGN-SR140N/S Battery

It does not react with sulfuric acid, hydrochloric acid, chlorine or any alkalis. At elevated temperatures carbon reacts with oxygen to form carbon oxides, and will reduce such metal oxides as iron oxide to the metal. This exothermic reaction is used in the iron and steel industry to control the carbon content of steel:

Fe3O4 + 4 C(s) ? 3 Fe(s) + 4 CO(g)

with sulfur to form carbon disulfide and with steam in the coal-gas reaction:Sony VAIO VGN-SR165E/B Battery

C(s) + H2O(g) ? CO(g) + H2(g).

Carbon combines with some metals at high temperatures to form metallic carbides, such as the iron carbide cementitein steel, and tungsten carbide, widely used as an abrasive and for making hard tips for cutting tools.

As of 2009, graphene appears to be the strongest material ever tested.However, the process of separating it fromgraphite will require some technological development before it is economical enough to be used in industrial processes.Sony VAIO VGN-SR165E/P Battery

Allotropes

Atomic carbon is a very short-lived species and, therefore, carbon is stabilized in various multi-atomic structures with different molecular configurations calledallotropes. The three relatively well-known allotropes of carbon are amorphous carbon, graphite, and diamond.Sony VAIO VGN-SR165E/S Battery

Once considered exotic, fullerenes are nowadays commonly synthesized and used in research; they include buckyballs, carbon nanotubes, carbon nanobuds and nanofibers. Several other exotic allotropes have also been discovered, such as lonsdaleite, glassy carbon, carbon nanofoam and linear acetylenic carbon (carbyne).Sony VAIO VGN-SR190EBJ Battery

The amorphous form is an assortment of carbon atoms in a non-crystalline, irregular, glassy state, which is essentially graphite but not held in a crystalline macrostructure. It is present as a powder, and is the main constituent of substances such as charcoal, lampblack (soot) and activated carbon. Sony VAIO VGN-SR190EBQ Battery

At normal pressures carbon takes the form of graphite, in which each atom is bonded trigonally to three others in a plane composed of fused hexagonal rings, just like those in aromatic hydrocarbons.The resulting network is 2-dimensional, and the resulting flat sheets are stacked and loosely bonded through weak van der Waals forces. Sony VAIO VGN-SR190EEJ/C Battery

This gives graphite its softness and its cleaving properties (the sheets slip easily past one another). Because of the delocalization of one of the outer electrons of each atom to form a ?-cloud, graphite conducts electricity, but only in the plane of each covalently bonded sheet. This results in a lower bulk electrical conductivity for carbon than for most metals.Sony VAIO VGN-SR190NAB Battery

The delocalization also accounts for the energetic stability of graphite over diamond at room temperature.

At very high pressures carbon forms the more compact allotrope diamond, having nearly twice the density of graphite. Here, each atom is bonded tetrahedrally to four others, thus making a 3-dimensional network of puckered six-membered rings of atoms.Sony VAIO VGN-SR190NBB Battery

Diamond has the same cubic structure as silicon and germanium and because of the strength of the carbon-carbon bonds, it is the hardest naturally occurring substance in terms of resistance to scratching. Contrary to the popular belief that "diamonds are forever", they are in fact thermodynamically unstable under normal conditions and transform into graphite.Sony VAIO VGN-SR190NDB Battery

However, due to a high activation energy barrier, the transition into graphite is so extremely slow at room temperature as to be unnoticeable. Under some conditions, carbon crystallizes as lonsdaleite. This form has a hexagonal crystal lattice where all atoms are covalently bonded. Therefore, all properties of lonsdaleite are close to those of diamond.Sony VAIO VGN-SR190NEB Battery

Fullerenes have a graphite-like structure, but instead of purely hexagonal packing, they also contain pentagons (or even heptagons) of carbon atoms, which bend the sheet into spheres, ellipses or cylinders. The properties of fullerenes (split into buckyballs, buckytubes and nanobuds) have not yet been fully analyzed and represent an intense area of research in nanomaterials.Sony VAIO VGN-SR190NGB Battery

The names "fullerene" and "buckyball" are given after Richard Buckminster Fuller, popularizer of geodesic domes, which resemble the structure of fullerenes. The buckyballs are fairly large molecules formed completely of carbon bonded trigonally, forming spheroids (the best-known and simplest is the soccerball-shaped C60 buckminsterfullerene).Sony VAIO VGN-SR190PAB Battery

Carbon nanotubes are structurally similar to buckyballs, except that each atom is bonded trigonally in a curved sheet that forms a hollow cylinder.Nanobuds were first reported in 2007 and are hybrid bucky tube/buckyball materials (buckyballs are covalently bonded to the outer wall of a nanotube) that combine the properties of both in a single structure.Sony VAIO VGN-SR190PCB Battery

Of the other discovered allotropes, carbon nanofoam is a ferromagnetic allotrope discovered in 1997. It consists of a low-density cluster-assembly of carbon atoms strung together in a loose three-dimensional web, in which the atoms are bonded trigonally in six- and seven-membered rings. It is among the lightest known solids, with a density of about 2 kg/m3.Sony VAIO VGN-SR190PFB Battery

Similarly, glassy carbon contains a high proportion of closed porosity, but contrary to normal graphite, the graphitic layers are not stacked like pages in a book, but have a more random arrangement. Linear acetylenic carbon has the chemical structure -(C:::C)n-. Carbon in this modification is linear with sp orbital hybridization, and is a polymer with alternating single and triple bonds.Sony VAIO VGN-SR19VN Battery

This type of carbyne is of considerable interest to nanotechnology as itsYoung's modulus is forty times that of the hardest known material – diamond.

Occurrence

Carbon is the fourth most abundant chemical element in the universe by mass after hydrogen, helium, and oxygen. Sony VAIO VGN-SR19VN Battery

Carbon is abundant in the Sun, stars, comets, and in the atmospheres of most planets. Some meteorites contain microscopic diamonds that were formed when the solar system was still a protoplanetary disk. Microscopic diamonds may also be formed by the intense pressure and high temperature at the sites of meteorite impacts. Sony VAIO VGN-SR19VRN Battery

In combination with oxygen in carbon dioxide, carbon is found in the Earth's atmosphere (approximately 810 gigatonnes of carbon) and dissolved in all water bodies (approximately 36,000 gigatonnes of carbon). Around 1,900 gigatonnes of carbon are present in the biosphere.Sony VAIO VGN-SR19XN Battery

Hydrocarbons (such as coal, petroleum, and natural gas) contain carbon as well—coal "reserves" (not "resources")amount to around 900 gigatonnes, and oil reserves around 150 gigatonnes. Proven sources of natural gas are about 175 1012 cubic metres (representing about 105 gigatonnes carbon), but it is estimated that there are also about 900 1012 cubic metres of "unconventional" gas such as shale gas, representing about 540 gigatonnes of carbon. Sony VAIO VGN-SR19XN Battery

(In the past, quantities of hydrocarbons were greater. In the period from 1751 to 2008 about 347 gigatonnes of carbon were released as carbon dioxide to the atmosphere from burning of fossil fuels. ) Carbon is also locked up as methane and methane hydrates in polar regions. It is estimated that at least 1,400 Gt of carbon is in this form just in (and under) the submarine permafrost of the Siberian Shelf.Sony VAIO VGN-SR210J/S Battery

Carbon is a major component in very large masses of carbonate rock (limestone, dolomite, marble and so on). Coal is the largest commercial source of mineral carbon, accounting for 4,000 gigatonnes or 80% of fossil carbon fuel.It is also rich in carbon – for example, anthracite contains 92–98%.Sony VAIO VGN-SR21M/S Battery

As for individual carbon allotropes, graphite is found in large quantities in the United States (mostly in New York and Texas),Russia, Mexico, Greenland, and India. Natural diamonds occur in the rock kimberlite, found in ancient volcanic "necks," or "pipes". Most diamond deposits are in Africa, notably in South Africa, Namibia, Botswana, the Republic of the Congo, and Sierra Leone. Sony VAIO VGN-SR21RM/H Battery

There are also deposits in Arkansas, Canada, the Russian Arctic, Brazil and in Northern and Western Australia. Diamonds are now also being recovered from the ocean floor off the Cape of Good Hope. However, though diamonds are found naturally, about 30% of all industrial diamonds used in the U.S. are now made synthetically.Sony VAIO VGN-SR21RM/S Battery

Carbon-14 is formed in upper layers of the troposphere and the stratosphere, at altitudes of 9–15 km, by a reaction that is precipitated by cosmic rays. Thermal neutrons are produced that collide with the nuclei of nitrogen-14, forming carbon-14 and a proton.Sony VAIO VGN-SR220J/B Battery

Isotopes

Isotopes of carbon are atomic nuclei that contain six protons plus a number of neutrons (varying from 2 to 16). Carbon has two stable, naturally occurring isotopes.[9] The isotope carbon-12 (12C) forms 98.93% of the carbon on Earth, while carbon-13 (13C) forms the remaining 1.07%.Sony VAIO VGN-SR220J/H Battery

The concentration of 12C is further increased in biological materials because biochemical reactions discriminate against 13C. In 1961 the International Union of Pure and Applied Chemistry (IUPAC) adopted the isotope carbon-12as the basis for atomic weights.Identification of carbon in NMR experiments is done with the isotope 13C.Sony VAIO VGN-SR240J/B Battery

Carbon-14 (14C) is a naturally occurring radioisotope which occurs in trace amounts on Earth of up to 1 part per trillion(0.0000000001%), mostly confined to the atmosphere and superficial deposits, particularly of peat and other organic materials. Sony VAIO VGN-SR240N/B Battery

This isotope decays by 0.158 MeV?- emission. Because of its relatively short half-life of 5730 years, 14C is virtually absent in ancient rocks, but is created in the upper atmosphere (lowerstratosphere and upper troposphere) by interaction of nitrogen with cosmic rays. The abundance of 14C in the atmosphere and in living organisms is almost constant, but decreases predictably in their bodies after death. Sony VAIO VGN-SR290JTH Battery

This principle is used in radiocarbon dating, invented in 1949, which has been used extensively to determine the age of carbonaceous materials with ages up to about 40,000 years.

There are 15 known isotopes of carbon and the shortest-lived of these is 8C which decays through proton emission and alpha decay and has a half-life of 1.98739x10?21s.Sony VAIO VGN-SR290JTJ Battery

The exotic 19C exhibits a nuclear halo, which means its radius is appreciably larger than would be expected if the nucleus were a sphere of constantdensity.

Formation in stars

Formation of the carbon atomic nucleus requires a nearly simultaneous triple collision of alpha particles (helium nuclei) within the core of a giant or supergiantstar which is known as the triple-alpha process,Sony VAIO VGN-SR290JTQ Battery

as the products of further nuclear fusion reactions of helium with hydrogen or another helium nucleus producelithium-5 and beryllium-8 respectively, both of which are highly unstable and decay almost instantly back into smaller nuclei. This happens in conditions of temperatures over 100 megakelvin and helium concentration that the rapid expansion and cooling of the early universe prohibited, and therefore no significant carbon was created during the Big Bang. Sony VAIO VGN-SR290JVB/C Battery

Instead, the interiors of stars in the horizontal branch transform three helium nuclei into carbon by means of this triple-alpha process. In order to be available for formation of life as we know it, this carbon must then later be scattered into space as dust, in supernova explosions, as part of the material which later forms second, third-generation star systems which have planets accreted from such dust.Sony VAIO VGN-SR290JVH/C Battery

The Solar System is one such third-generation star system. Another of the fusion mechanisms powering stars is the CNO cycle, in which carbon acts as a catalyst to allow the reaction to proceed.

Rotational transitions of various isotopic forms of carbon monoxide (for example, 12CO, 13CO, and C18O) are detectable in the submillimeter wavelength range, and are used in the study of newly forming stars in [[molecular clouds.Sony VAIO VGN-SR290NTB Battery

Carbon cycle

Under terrestrial conditions, conversion of one element to another is very rare. Therefore, the amount of carbon on Earth is effectively constant. Thus, processes that use carbon must obtain it somewhere and dispose of it somewhere else. Sony VAIO VGN-SR29VN/S Battery

The paths that carbon follows in the environment make up the carbon cycle. For example, plants draw carbon dioxide out of their environment and use it to build biomass, as in carbon respiration or the Calvin cycle, a process of carbon fixation. Some of this biomass is eaten by animals, whereas some carbon is exhaled by animals as carbon dioxide. Sony VAIO VGN-SR29XN/S Battery

The carbon cycle is considerably more complicated than this short loop; for example, some carbon dioxide is dissolved in the oceans; dead plant or animal matter may become petroleum or coal, which can burn with the release of carbon, should bacteria not consume it.Sony VAIO VGN-SR2RVN/S Battery

Organic compounds

Carbon has the ability to form very long chains of interconnecting C-C bonds. This property is called catenation. Carbon-carbon bonds are strong, and stable. This property allows carbon to form an almost infinite number of compounds; Sony VAIO VGN-SR390NAB Battery

in fact, there are more known carbon-containing compounds than all the compounds of the other chemical elements combined except those of hydrogen (because almost all organic compounds contain hydrogen too).

The simplest form of an organic molecule is the hydrocarbon—a large family of organic molecules that are composed of hydrogen atoms bonded to a chain of carbon atoms. Sony VAIO VGN-SR390NAH Battery

Chain length, side chains and functional groups all affect the properties of organic molecules. ByIUPAC's definition, all the other organic compounds are functionalized compounds of hydrocarbons.

Carbon occurs in all known organic life and is the basis of organic chemistry. Sony VAIO VGN-SR41M/P Battery

When united with hydrogen, it forms various hydrocarbons which are important to industry as refrigerants,lubricants, solvents, as chemical feedstock for the manufacture of plastics andpetrochemicals and as fossil fuels.

When combined with oxygen and hydrogen, carbon can form many groups of important biological compounds includingsugars, lignans, chitins, alcohols, fats, and aromatic esters, carotenoids and terpenes. Sony VAIO VGN-SR41M/S Battery

With nitrogen it formsalkaloids, and with the addition of sulfur also it forms antibiotics, amino acids, and rubber products. With the addition of phosphorus to these other elements, it forms DNA and RNA, the chemical-code carriers of life, andadenosine triphosphate (ATP), the most important energy-transfer molecule in all living cells.Sony VAIO VGN-SR49VN/H Battery

Inorganic compounds

Commonly carbon-containing compounds which are associated with minerals or which do not contain hydrogen or fluorine, are treated separately from classical organic compounds; however the definition is not rigid (see reference articles above). Among these are the simple oxides of carbon. The most prominent oxide is carbon dioxide (CO2).Sony VAIO VGN-SR51B/P Battery

This was once the principal constituent of the paleoatmosphere, but is a minor component of the Earth's atmosphere today.Dissolved in water, it forms carbonic acid (H2CO3), but as most compounds with multiple single-bonded oxygens on a single carbon it is unstable. Through this intermediate, though, resonance-stabilized carbonate ions are produced. Sony VAIO VGN-SR51B/S Battery

Some important minerals are carbonates, notably calcite. Carbon disulfide (CS2) is similar.

The other common oxide is carbon monoxide (CO). It is formed by incomplete combustion, and is a colorless, odorless gas. The molecules each contain a triple bond and are fairly polar, resulting in a tendency to bind permanently to hemoglobin molecules, displacing oxygen, which has a lower binding affinity.Sony VAIO VGN-SR51MF Battery

Cyanide (CN–), has a similar structure, but behaves much like a halide ion (pseudohalogen). For example it can form the nitride cyanogen molecule ((CN)2), similar to diatomic halides. Other uncommon oxides are carbon suboxide (C3O2), the unstable dicarbon monoxide (C2O), carbon trioxide (CO3), cyclopentanepentone (C5O5) cyclohexanehexone (C6O6), and mellitic anhydride (C12O9).Sony VAIO VGN-SR51MF/P Battery

With reactive metals, such as tungsten, carbon forms either carbides (C4–), or acetylides (C2?
2) to form alloys with high melting points. These anions are also associated with methane and acetylene, both very weak acids. With an electronegativity of 2.5, carbon prefers to form covalent bonds. Sony VAIO VGN-SR51MF/S Battery

A few carbides are covalent lattices, like carborundum (SiC), which resembles diamond.

Organometallic compounds

Organometallic compounds by definition contain at least one carbon-metal bond. A wide range of such compounds exist; major classes include simple alkyl-metal compounds (for example, tetraethyllead), ?2-alkene compounds (for example, Zeise's salt),Sony VAIO VGN-SR51MF/W Battery

and ?3-allyl compounds (for example, allylpalladium chloride dimer);metallocenes containing cyclopentadienyl ligands (for example, ferrocene); and transition metal carbene complexes. Many metal carbonyls exist (for example,tetracarbonylnickel); some workers consider the carbon monoxide ligand to be purely inorganic, and not organometallic.Sony VAIO VGN-SR51MR Battery

While carbon is understood to exclusively form four bonds, an interesting compound containing an octahedral hexacoordinated carbon atom has been reported. The cation of the compound is [(Ph3PAu)6C]2+. This phenomenon has been attributed to the aurophilicity of the gold ligands.Sony VAIO VGN-SR59VG Battery

History and etymology

The English name carbon comes from the Latin carbo for coal and charcoal, whence also comes the French charbon, meaning charcoal. InGerman, Dutch and Danish, the names for carbon are Kohlenstoff, koolstof and kulstof respectively, all literally meaning coal-substance.Sony VAIO VGN-SR59VG/H Battery

Carbon was discovered in prehistory and was known in the forms of soot and charcoal to the earliest human civilizations. Diamonds were known probably as early as 2500 BCE in China, while carbon in the form of charcoal was made around Roman times by the same chemistry as it is today, by heating wood in a pyramid covered with clay to exclude air.Sony VAIO VGN-SR70B/S Battery

In 1722, René Antoine Ferchault de Réaumur demonstrated that iron was transformed into steel through the absorption of some substance, now known to be carbon. In 1772, Antoine Lavoisier showed that diamonds are a form of carbon; when he burned samples of charcoal and diamond and found that neither produced any water and that both released the same amount of carbon dioxide per gram. Sony VAIO VGN-SR72B/P Battery

In 1779, Carl Wilhelm Scheele showed that graphite, which had been thought of as a form of lead, was instead identical with charcoal but with a small admixture of iron, and that it gave "aerial acid" (his name for carbon dioxide) when oxidized with nitric acid. In 1786, the French scientists Claude Louis Berthollet, Gaspard Monge and C. A. Sony VAIO VGN-SR72B/S Battery

Vandermonde confirmed that graphite was mostly carbon by oxidizing it in oxygen in much the same way Lavoisier had done with diamond. Some iron again was left, which the French scientists thought was necessary to the graphite structure. However, in their publication they proposed the name carbone (Latin carbonum) for the element in graphite which was given off as a gas upon burning graphite.Sony VAIO VGN-SR73JB/S Battery

Antoine Lavoisier then listed carbon as an element in his 1789 textbook.

A new allotrope of carbon, fullerene, that was discovered in 1985 includes nanostructured forms such as buckyballs and nanotubes.Their discoverers – Robert Curl, Harold Kroto and Richard Smalley – received the Nobel Prize in Chemistry in 1996.Sony VAIO VGN-SR74FB/S Battery

The resulting renewed interest in new forms lead to the discovery of further exotic allotropes, including glassy carbon, and the realization that "amorphous carbon" is not strictly amorphous.

Graphite

Commercially viable natural deposits of graphite occur in many parts of the world, but the most important sources economically are in China, India, Brazil and North Korea.Sony VAIO VGN-SR90FS Battery

Graphite deposits are of metamorphic origin, found in association with quartz, mica and feldspars in schists, gneisses and metamorphosed sandstones andlimestone as lenses or veins, sometimes of a meter or more in thickness. Deposits of graphite in Borrowdale, Cumberland, Sony VAIO VGN-SR90NS Battery

England were at first of sufficient size and purity that, until the 19th century, pencils were made simply by sawing blocks of natural graphite into strips before encasing the strips in wood. Today, smaller deposits of graphite are obtained by crushing the parent rock and floating the lighter graphite out on water.Sony VAIO VGN-SR90S Battery

There are three types of natural graphite—amorphous, flake or crystalline flake, and vein or lump. Amorphous graphite is the lowest quality and most abundant. Contrary to science, in industry "amorphous" refers to very small crystal size rather than complete lack of crystal structure. Amorphous is used for lower value graphite products and is the lowest priced graphite.Sony VAIO VGN-SR90US Battery

Large amorphous graphite deposits are found in China, Europe, Mexico and the United States. Flake graphite is less common and of higher quality than amorphous; it occurs as separate plates that crystallized in metamorphic rock. Flake graphite can be four times the price of amorphous. Good quality flakes can be processed into expandable graphite for many uses, such as flame retardants. Sony VAIO VGN-SR91NS Battery

The foremost deposits are found in Austria, Brazil, Canada, China, Germany and Madagascar. Vein or lump graphite is the rarest, most valuable, and highest quality type of natural graphite. It occurs in veins along intrusive contacts in solid lumps, and it is only commercially mined in Sri Lanka.Sony VAIO VGN-SR91PS Battery

According to the USGS, world production of natural graphite was 1.1 million tonnes in 2010, to which China contributed 800,00 t, India 130,000 t, Brazil 76,000 t, North Korea 30,000 t and Canada 25,000 t. No natural graphite was reported mined in the United States, but 118,000 t of synthetic graphite with an estimated value of $998 million was produced in 2009.Sony VAIO VGN-SR91S Battery

Diamond

The diamond supply chain is controlled by a limited number of powerful businesses, and is also highly concentrated in a small number of locations around the world (see figure).

Only a very small fraction of the diamond ore consists of actual diamonds. Sony VAIO VGN-SR91US Battery

The ore is crushed, during which care has to be taken in order to prevent larger diamonds from being destroyed in this process and subsequently the particles are sorted by density. Today, diamonds are located in the diamond-rich density fraction with the help of X-ray fluorescence, after which the final sorting steps are done by hand. Sony VAIO VGN-SR92NS Battery

Before the use of X-rays became commonplace, the separation was done with grease belts; diamonds have a stronger tendency to stick to grease than the other minerals in the ore.

Historically diamonds were known to be found only in alluvial deposits in southern India. Sony VAIO VGN-SR92PS Battery

India led the world in diamond production from the time of their discovery in approximately the 9th century BCE to the mid-18th century AD, but the commercial potential of these sources had been exhausted by the late 18th century and at that time India was eclipsed by Brazil where the first non-Indian diamonds were found in 1725.Sony VAIO VGN-SR92S Battery

Diamond production of primary deposits (kimberlites and lamproites) only started in the 1870s after the discovery of the Diamond fields in South Africa. Production has increased over time and now an accumulated total of 4.5 billion carats have been mined since that date.Sony VAIO VGN-SR92US Battery

Interestingly 20% of that amount has been mined in the last 5 years alone and during the last ten years 9 new mines have started production while 4 more are waiting to be opened soon. Most of these mines are located in Canada, Zimbabwe, Angola, and one in Russia.Sony VAIO VGN-SR93DS Battery

In the United States, diamonds have been found in Arkansas, Colorado and Montana. In 2004, a startling discovery of a microscopic diamond in the United States led to the January 2008 bulk-sampling of kimberlite pipes in a remote part of Montana.

Today, most commercially viable diamond deposits are in Russia, Botswana, Australia and the Democratic Republic of Congo.Sony VAIO VGN-SR93JS Battery

In 2005, Russia produced almost one-fifth of the global diamond output, reports the British Geological Survey. Australia has the richest diamantiferous pipe with production reaching peak levels of 42 metric tons (41 long tons; 46 short tons) per year in the 1990s.Sony VAIO VGN-SR93PS Battery

There are also commercial deposits being actively mined in the Northwest Territories of Canada,Siberia (mostly in Yakutia territory; for example, Mir pipe and Udachnaya pipe), Brazil, and in Northern and Western Australia.

Applications

Carbon is essential to all known living systems, and without it life as we know it could not exist (see alternative biochemistry). Sony VAIO VGN-SR93YS Battery

The major economic use of carbon other than food and wood is in the form of hydrocarbons, most notably the fossil fuel methane gas and crude oil(petroleum). Crude oil is used by the petrochemical industry to produce, amongst others,gasoline and kerosene, through a distillation process, in refineries. Sony VAIO VGN-SR94FS Battery

Cellulose is a natural, carbon-containing polymer produced by plants in the form of cotton, linen, and hemp. Celluloseis mainly used for maintaining structure in plants. Commercially valuable carbon polymers of animal origin include wool, cashmere and silk. Plastics are made from synthetic carbon polymers, often with oxygen and nitrogen atoms included at regular intervals in the main polymer chain. Sony VAIO VGN-SR94GS Battery

The raw materials for many of these synthetic substances come from crude oil.

The uses of carbon and its compounds are extremely varied. It can form alloys with iron, of which the most common is carbon steel. Graphite is combined with clays to form the 'lead' used in pencils used for writing and drawing. Sony VAIO VGN-SR94HS Battery

It is also used as a lubricant and a pigment, as a molding material in glass manufacture, in electrodes for dry batteries and in electroplatingand electroforming, in brushes for electric motors and as a neutron moderator in nuclear reactors.

Charcoal is used as a drawing material in artwork, for grilling, and in many other uses including iron smelting. Sony VAIO VGN-SR94VS Battery

Wood, coal and oil are used as fuel for production of energy and space heating. Gem quality diamond is used in jewelry, and Industrial diamonds are used in drilling, cutting and polishing tools for machining metals and stone. Plastics are made from fossil hydrocarbons, and carbon fiber, made by pyrolysis of synthetic polyester fibers is used to reinforce plastics to form advanced, lightweight composite materials. Sony VAIO VGN-SZ35B/B Battery

Carbon fiber is made by pyrolysis of extruded and stretched filaments of polyacrylonitrile (PAN) and other organic substances.

Carbon black is used as the black pigment in printing ink, artist's oil paint and water colours, carbon paper, automotive finishes, India ink and laser printer toner. Carbon black is also used as a filler in rubber products such as tyres and in plastic compounds. Sony VAIO VGN-SZ54B/B Battery

Activated charcoal is used as an absorbent and adsorbent in filter material in applications as diverse as gas masks, water purification and kitchen extractor hoods and in medicine to absorb toxins, poisons, or gases from the digestive system. Carbon is used in chemical reduction at high temperatures. Coke is used to reduce iron ore into iron. Sony VAIO VGN-SZ55B/B Battery

Case hardening of steel is achieved by heating finished steel components in carbon powder. Carbides of silicon, tungsten, boronand titanium, are among the hardest known materials, and are used as abrasives in cutting and grinding tools. Carbon compounds make up most of the materials used in clothing, such as natural and synthetic textiles and leather, and almost all of the interior surfaces in the built environment other than glass, stone and metal.Sony VAIO VGN-SZ55GN/B Battery

Diamonds

The diamond industry can be broadly separated into two basically distinct categories: one dealing with gem-grade diamonds and another for industrial-grade diamonds. While a large trade in both types of diamonds exists, the two markets act in dramatically different ways.Sony VAIO VGN-SZ56 Battery

A large trade in gem-grade diamonds exists. Unlike precious metals such as gold or platinum, gem diamonds do not trade as a commodity: there is a substantial mark-up in the sale of diamonds, and there is not a very active market for resale of diamonds.Sony VAIO VGN-SZ561N Battery

The market for industrial-grade diamonds operates much differently from its gem-grade counterpart. Industrial diamonds are valued mostly for their hardness and heat conductivity, making many of the gemological characteristics of diamond, including clarity and color, mostly irrelevant. Sony VAIO VGN-SZ562N Battery

This helps explain why 80% of mined diamonds (equal to about 100 million carats or 20 tonnes annually), unsuitable for use as gemstones and known as bort, are destined for industrial use. In addition to mined diamonds, synthetic diamonds found industrial applications almost immediately after their invention in the 1950s; another 3 billion carats (600 tonnes) of synthetic diamond is produced annually for industrial use.Sony VAIO VGN-SZ57N Battery

The dominant industrial use of diamond is in cutting, drilling, grinding, and polishing. Most uses of diamonds in these technologies do not require large diamonds; in fact, most diamonds that are gem-quality except for their small size, can find an industrial use. Diamonds are embedded in drill tips or saw blades, or ground into a powder for use in grinding and polishing applications.Sony VAIO VGN-SZ58GN Battery

Specialized applications include use in laboratories as containment for high pressure experiments (see diamond anvil cell), high-performance bearings, and limited use in specialized windows. With the continuing advances being made in the production of synthetic diamonds, future applications are beginning to become feasible. Sony VAIO VGN-SZ58GN/C Battery

Garnering much excitement is the possible use of diamond as a semiconductor suitable to build microchips from, or the use of diamond as a heat sink in electronics.

Precautions

Pure carbon has extremely low toxicity to humans and can be handled and even ingested safely in the form of graphite or charcoal.Sony VAIO VGN-SZ58N Battery

It is resistant to dissolution or chemical attack, even in the acidic contents of the digestive tract, for example. Consequently once it enters into the body's tissues it is likely to remain there indefinitely. Carbon black was probably one of the first pigments to be used fortattooing, and Ötzi the Iceman was found to have carbon tattoos that survived during his life and for 5200 years after his death.Sony VAIO VGN-SZ61MN/B Battery

However, inhalation of coal dust or soot (carbon black) in large quantities can be dangerous, irritating lung tissues and causing the congestive lung disease coalworker's pneumoconiosis. Similarly, diamond dust used as an abrasive can do harm if ingested or inhaled. Microparticles of carbon are produced in diesel engine exhaust fumes, and may accumulate in the lungs.Sony VAIO VGN-SZ61VN/X Battery

In these examples, the harmful effects may result from contamination of the carbon particles, with organic chemicals or heavy metals for example, rather than from the carbon itself.

Carbon generally has low toxicity to almost all life on Earth; however, to some creatures it can still be toxic – for instance, carbon nanoparticles are a deadly toxins to Drosophila.Sony VAIO VGN-SZ61WN/C Battery

Carbon may also burn vigorously and brightly in the presence of air at high temperatures, as in the Windscale fire, which was caused by sudden release of stored Wigner energy in the graphite core. Large accumulations of coal, which have remained inert for hundreds of millions of years in the absence of oxygen, may spontaneously combust when exposed to air, for example in coal mine waste tips.Sony VAIO VGN-SZ640N/B Battery

The great variety of carbon compounds include such lethal poisons as tetrodotoxin, the lectin ricin from seeds of the castor oil plantRicinus communis, cyanide (CN-) and carbon monoxide; and such essentials to life as glucose and protein.

A carbon footprint has historically been defined as "the total set of greenhouse gas (GHG) emissions caused by an organization, event, product or person."Sony VAIO VGN-SZ645P3 Battery

However, calculating a carbon footprint which conforms to this definition is often impracticable due to the large amount of data required, which is often costly and time consuming to obtain. A more practicable definition has been suggested, which is gaining acceptance within the field:Sony VAIO VGN-SZ650N/C Battery

"A measure of the total amount of carbon dioxide (CO2) and methane (CH4) emissions of a defined population, system or activity, considering all relevant sources, sinks and storage within the spatial and temporal boundary of the population, system or activity of interest. Calculated as carbon dioxide equivalent (CO2e) using the relevant 100-year global warming potential (GWP100)."Sony VAIO VGN-SZ660N/C Battery

Greenhouse gases can be emitted through transport, land clearance, and the production and consumption of food, fuels, manufactured goods, materials, wood, roads, buildings, and services.[3] For simplicity of reporting, it is often expressed in terms of the amount of carbon dioxide, or its equivalent of other GHGs, emitted.Sony VAIO VGN-SZ670N/C Battery

The concept name of the carbon footprint originates from ecological footprint discussion. The carbon footprint is a subset of theecological footprint and of the more comprehensive Life Cycle Assessment (LCA).

An individual's, nation's, or organisations carbon footprint can be measured by undertaking a GHG emissions assessment. Sony VAIO VGN-SZ680ND Battery

Once the size of a carbon footprint is known, a strategy can be devised to reduce it, e.g. by technological developments, better process and product management, changed Green Public or Private Procurement (GPP), carbon capture, consumption strategies, and others.Sony VAIO VGN-SZ691N/X Battery

The mitigation of carbon footprints through the development of alternative projects, such as solar or wind energy or reforestation, represents one way of reducing a carbon footprint and is often known as Carbon offsetting.

The main influences on carbon footprints include population, economic output, and energy and carbon intensity of the economy.Sony VAIO VGN-SZ71E/B Battery

These factors are the main targets of individuals and businesses in order to decrease carbon footprints. Scholars suggest the most effective way to decrease a carbon footprint is to either decrease the amount of energy needed for production or to decrease the dependence on carbon emitting fuels.Sony VAIO VGN-SZ71VN/X Battery

Of products

Several organizations have calculated carbon footprints of products; The US Environmental Protection Agency has addressed paper, plastic (candy wrappers), glass, cans, computers, carpet and tires. Australia has addressed lumber and other building materials. Academics in Australia, Korea and the US have addressed paved roads.Sony VAIO VGN-SZ71WN/C Battery

Companies, nonprofits and academics have addressed manufacture and operation of cars, buses, trains, airplanes, ships and pipelines. The US Postal Service has addressed mailing letters and packages. Carnegie Mellon University has estimated the CO2footprints of 46 large sectors of the economy in each of eight countries. Sony VAIO VGN-SZ74B/B Battery

Carnegie Mellon, Sweden and the Carbon Trust have addressed foods at home and in restaurants.

The Carbon Trust has worked with UK manufacturers on foods, shirts and detergents, introducing a CO2 label in March 2007. The label is intended to comply with a new British Publicly Available Specification (i.e. not a standard), PAS 2050, and is being actively piloted by The Carbon Trust and various industrial partners. Sony VAIO VGN-SZ750N/C Battery

Evaluating the package of some products is key to figuring out the carbon footprint. The key ways to determine the carbon footprint is to look at the materials that were used to make the item. For example, the juice carton is made of Aseptic carton, the beer can is made of aluminum and some water bottles either made of glass or plastic. The larger the size, the larger the footprint will be.Sony VAIO VGN-SZ75B/B Battery

Of electricity

The following table compares, from peer-reviewed studies of full life cycle emissions and from various other studies, the carbon footprint of various forms of energy generation: Nuclear, Hydro, Coal, Gas, Solar Cell, Peat and Wind generation technology.Sony VAIO VGN-SZ76 Battery

Note: 3.6 MJ = megajoule(s) == 1 kW·h = kilowatt-hour(s), thus 1 g/MJ = 3.6 g/kW·h.
Legend: B = Black coal (supercritical)–(new subcritical), Br = Brown coal (new subcritical), cc = combined cycle, oc = open cycle, TL= low-temperature/closed-circuit (geothermal doublet), TH = high-temperature/open-circuit, WL = Light Water Reactors, WH= Heavy Water Reactors, #Educated estimate.Sony VAIO VGN-SZ770N/C Battery

These studies thus concluded that hydroelectric, wind, and nuclear power always produced the least CO2 per kilowatt-hour of any other electricity sources. These figures do not allow for emissions due to accidents or terrorism. Renewable electricity generation methods, for example wind power and hydropower, emit no carbon from the operation, but do leave a footprint during construction phase and maintenance during operation.Sony VAIO VGN-SZ77N Battery

Of Heat and various combined heat and power schemes, heat pumps etc ...

The previous table gives the carbon footprint per kilowatt-hour of electricity generated, which is about half the world's man-made CO2 output. The CO2 footprint for heat is equally significant and research shows that using waste heat from power generation in combined heat and power district heating, chp/dh has the lowest carbon footprint. much lower than micro-power or heat pumps.Sony VAIO VGN-SZ780 Battery

Kyoto Protocol, carbon offsetting, and certificates

Carbon dioxide emissions into the atmosphere, and the emissions of other GHGs, are often associated with the burning of fossil fuels, like natural gas, crude oil and coal.Sony VAIO VGN-SZ78N Battery

The Kyoto Protocol defines legally binding targets and timetables for cutting the GHG emissions of industrialized countries that ratified the Kyoto Protocol. Accordingly, from an economic or market perspective, one has to distinguish between a mandatory market and a voluntary market. Typical for both markets is the trade with emission certificates:Sony VAIO VGN-SZ791N/X Battery

• Certified Emission Reduction (CER)
• Emission Reduction Unit (ERU)
• Verified Emission Reduction (VER)

Mandatory market mechanisms

To reach the goals defined in the Kyoto Protocol, with the least economical costs, the following flexible mechanisms were introduced for the mandatory market:Sony VAIO VGN-SZ84NS Battery

• Clean Development Mechanism (CDM)
• Joint Implementation (JI)
• Emissions trading

The CDM and JI mechanisms requirements for projects which create a supply of emission reduction instruments, while Emissions Trading allows those instruments to be sold on international markets.Sony VAIO VGN-SZ84PS Battery

- Projects which are compliant with the requirements of the CDM mechanism generate Certified Emissions Reductions (CERs).
- Projects which are compliant with the requirements of the JI mechanism generate Emissions Reduction Units (ERUs).

The CERs and ERUs can then be sold through Emissions Trading. The demand for the CERs and ERUs being traded is driven by:Sony VAIO VGN-SZ84S Battery

- Shortfalls in national emission reduction obligations under the Kyoto Protocol.
- Shortfalls amongst entities obligated under local emissions reduction schemes.

Nations which have failed to deliver their Kyoto emissions reductions obligations can enter Emissions Trading to purchase CERS and ERUs to cover their treaty shortfalls.Sony VAIO VGN-SZ84US Battery

Nations and groups of nations can also create local emission reduction schemes which place mandatory carbon dioxide emission targets on entities within their national boundaries. If the rules of a scheme allow, the obligated entities may be able to cover all or some of any reduction shortfalls by purchasing CERs and ERUs through Emissions Trading. Sony VAIO VGN-SZ85NS Battery

While local emissions reduction schemes have no status under the Kyoto Protocol itself, they play a prominent role in creating the demand for CERs and ERUs, stimulating Emissions Trading and setting a market price for emissions.

A well-known mandatory local emissions trading scheme is the EU Emissions Trading Scheme (EU ETS).Sony VAIO VGN-SZ85S Battery

New changes are being made to the trading schemes. The EU Emissions Trading Scheme is set to make some new changes within the next year. The new changes will target the emissions produced by flight travel in and out of the European Union.

Other nations are scheduled to start participating in Emissions Trading Schemes within the next few year. These nations include China, India and the United States.Sony VAIO VGN-SZ85US Battery

Voluntary market mechanisms

In contrast to the strict rules set out for the mandatory market, the voluntary market provides companies with different options to acquire emissions reductions. A solution, comparable with those developed for the mandatory market, has been developed for the voluntary market, the Verified Emission Reductions (VER). Sony VAIO VGN-SZ94NS Battery

This measure has the great advantage that the projects/activities are managed according to the quality standards set out for CDM/JI projects but the certificates provided are not registered by the governments of the host countries or the Executive Board of the UNO. As such, high quality VERs can be acquired at lower costs for the same project quality. Sony VAIO VGN-SZ94PS Battery

However, at present VERs can not be used in the mandatory market.

The voluntary market in North America is divided between members of the Chicago Climate Exchange and the Over The Counter (OTC) market. The Chicago Climate Exchangeis a voluntary yet legally binding cap-and-trade emission scheme whereby members commit to the capped emission reductions and must purchase allowances from other members or offset excess emissions.Sony VAIO VGN-SZ94S Battery

The OTC market does not involve a legally binding scheme and a wide array of buyers from the public and private spheres, as well as special events that want to go carbon neutral.

There are project developers, wholesalers, brokers, and retailers, as well as carbon funds, in the voluntary market. Some businesses and nonprofits in the voluntary market encompass more than just one of the activities listed above. Sony VAIO VGN-SZ94US Battery

A report by Ecosystem Marketplace shows that carbon offset prices increase as it moves along the supply chain—from project developer to retailer.

While some mandatory emission reduction schemes exclude forest projects, these projects flourish in the voluntary markets.Sony VAIO VGN-SZ95NS Battery

A major criticism concerns the imprecise nature of GHG sequestration quantification methodologies for forestry projects. However, others note the community co-benefits that forestry projects foster. Project types in the voluntary market range from avoided deforestation, afforestation/reforestation, industrial gas sequestration, increased energy efficiency, fuel switching, methane capture from coal plants and livestock, and even renewable energy. Sony VAIO VGN-SZ95S Battery

Renewable Energy Certificates (RECs) sold on the voluntary market are quite controversial due to additionality concerns.Industrial Gas projects receive criticism because such projects only apply to large industrial plants that already have high fixed costs. Siphoning off industrial gas for sequestration is considered picking the low hanging fruit; which is why credits generated from industrial gas projects are the cheapest in the voluntary market.Sony VAIO VGN-SZ95US Battery

The size and activity of the voluntary carbon market is difficult to measure. The most comprehensive report on the voluntary carbon markets to date was released by Ecosystem Marketplace and New Carbon Finance in July 2007.

ÆON of Japan is firstly approved by Japanese authority to indicate carbon footprint on three private brand goods in October 2009.Sony VAIO VGN-TZ121 Battery

Amorphous carbon or free, reactive carbon, is an allotrope of carbon that does not have any crystalline structure. As with allglassy materials, some short-range order can be observed. Amorphous carbon is often abbreviated to aC for general amorphous carbon, aC:H for hydrogenated amorphous carbon, or to ta-C for tetrahedral amorphous carbon (also called diamond-like carbon).Sony VAIO VGN-TZ13 Battery

In mineralogy, amorphous carbon is the name used for coal, soot and other impure forms of the element, carbon that are neither graphite nor diamond. In a crystallographic sense, however, these materials are not truly amorphous, but are polycrystalline or nanocrystalline materials of graphite or diamond within an amorphous carbon matrix.Sony VAIO VGN-TZ130N/B Battery

In mineralogy

Historically, the term "amorphous carbon" was used to describe carbonaceous materials found in soot and coal that could not be categorized as either diamond or graphite. However, these materials are not truly amorphous, but consist of crystallites of graphite[1] or diamond[2] technically polycrystalline or nanocrystalline materials. Sony VAIO VGN-TZ131 Battery

Commercial carbon also usually contains significant quantities of other elements, which may form crystalline impurities.

Coal and soot are both informally called amorphous carbon. However, both are products of pyrolysis, which does not produce true amorphous carbon under normal conditions. Sony VAIO VGN-TZ132/N Battery

The coal industry divides coal up into various grades depending on the amount of carbon present in the sample compared to the amount of impurities. The highest grade, anthracite, is about 90 percent carbon and 10% other elements. Bituminous coal is about 75-90 percent carbon, and lignite is the name for coal that is around 55 percent carbon.Sony VAIO VGN-TZ132N Battery

In modern science

With the development of modern thin film deposition and growth techniques in the latter half of the 20th century, such as chemical vapour deposition, sputter deposition, and cathodic arc deposition, it became possible to fabricate truly amorphous carbon materials.Sony VAIO VGN-TZ150N/B Battery

In technical terms, true amorphous carbon has localized ? electrons (as opposed to the aromatic ? bonds in graphite), and its bonds form with lengths and distances that are inconsistent with any other allotrope of carbon. It also contains a high concentration of dangling bonds, which cause deviations in interatomic spacing (as measured using diffraction) of more than 5%, and noticeable variation in bond angle.Sony VAIO VGN-TZ150N/N Battery

The properties of amorphous carbon films vary depending on the parameters used during deposition. One of the most common ways to characterize amorphous carbon is through the ratio of sp2 to sp3 hybridized bonds present in the material. Graphite consists purely of sp2 hybridized bonds, whereas diamond consists purely of sp3hybridized bonds. Sony VAIO VGN-TZ160CB Battery

Materials that are high in sp3 hybridized bonds are referred to as tetrahedral amorphous carbon (owing to the tetrahedral shape formed by sp3hybridized bonds) or as diamond-like carbon (owing to the similarity of many physical properties to those of diamond).Sony VAIO VGN-TZ160N/B Battery

Experimentally, sp2 to sp3 ratios can be determined by comparing the relative intensities of various spectroscopic peaks (including EELS, XPS, and Raman Spectroscopy) to those expected for graphite or diamond. In theoretical works, the sp2 to sp3 ratios are often obtained by counting the number of carbon atoms with three bonded neighbors versus those with four bonded neighbors.Sony VAIO VGN-TZ16GN/B Battery

(Note that this relies heavily on deciding on a 'cutoff' distance that determines whether neighbouring atoms are bonded or not, and is therefore merely used as an indication of the relative sp2-sp3 ratio.)

Although the characterization of amorphous carbon materials by the sp2-sp3 ratio may seem to indicate a one-dimensional range of properties between graphite and diamond, this is most definitely not the case.Sony VAIO VGN-TZ16N Battery

Research is currently ongoing into ways to characterize and expand on the range of properties offered by amorphous carbon materials.

Amorphous carbon materials may also be stabilized by terminating dangling-? bonds with hydrogen. These materials are then called hydrogenated amorphous carbon.

All practical forms of hydrogenated carbon—including cigarette smoke, wood fire smoke, chimney soot, mined coal such as bitumen and anthracite—contain large amounts of polycyclic aromatic hydrocarbon tars, and are therefore almost certainly carcinogenic.Sony VAIO VGN-TZ16N/B Battery

Carbon nanotubes (CNTs) are allotropes of carbon with a cylindrical nanostructure. Nanotubes have been constructed with length-to-diameter ratio of up to 132,000,000:1, significantly larger than for any other material. These cylindrical carbon molecules have unusual properties, which are valuable for nanotechnology, electronics, optics and other fields of materials science and technology. Sony VAIO VGN-TZ17/N Battery

In particular, owing to their extraordinary thermal conductivity and mechanical and electrical properties, carbon nanotubes may find applications as additives to various structural materials.

Nanotubes are members of the fullerene structural family, which also includes the spherical buckyballs, and the ends of a nanotube may be capped with a hemisphere of the buckyball structure. Sony VAIO VGN-TZ170N/B Battery

Their name is derived from their long, hollow structure with the walls formed by one-atom-thick sheets of carbon, called graphene. These sheets are rolled at specific and discrete ("chiral") angles, and the combination of the rolling angle and radius decides the nanotube properties; for example, whether the individual nanotube shell is ametal or semiconductor. Sony VAIO VGN-TZ170N/N Battery

Nanotubes are categorized as single-walled nanotubes (SWNTs) and multi-walled nanotubes (MWNTs). Individual nanotubes naturally align themselves into "ropes" held together by van der Waals forces.

Applied quantum chemistry, specifically, orbital hybridization best describes chemical bonding in nanotubes.Sony VAIO VGN-TZ17GN/B Battery

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 inalkanes, provide nanotubules with their unique strength.

Most single-walled nanotubes (SWNT) have a diameter of close to 1 nanometer, with a tube length that can be many millions of times longer. Sony VAIO VGN-TZ17N Battery

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 (n,m) . The integers n and m denote the number of unit vectors along two directions in the honeycomb crystal latticeof graphene.Sony VAIO VGN-TZ18/N Battery

If m = 0, the nanotubes are called zigzag nanotubes, and if n = m, the nanotubes are called armchair nanotubes. Otherwise, they are called chiral. The diameter of an ideal nanotube can be calculated from its (n,m) indices as follows

where a = 0.246 nm.Sony VAIO VGN-TZ180N/RC Battery

SWNTs are an important variety of carbon nanotube because most of their properties change significantly with the (n,m) values, and this dependence is non-monotonic (see Kataura plot). In particular, their band gap can vary from zero to about 2 eV and their electrical conductivity can show metallic or semiconducting behavior. Sony VAIO VGN-TZ185N/WC Battery

One useful application of SWNTs is in the development of the first intramolecular field-effect transistors (FET). Production of the first intramolecular logic gate using SWNT FETs has recently become possible as well. To create a logic gate you must have both a p-FET and an n-FET. Sony VAIO VGN-TZ18GN/X Battery

Because SWNTs are p-FETs when exposed to oxygen and n-FETs otherwise, it is possible to protect half of an SWNT from oxygen exposure, while exposing the other half to oxygen. This results in a single SWNT that acts as a NOT logic gate with both p and n-type FETs within the same molecule.Sony VAIO VGN-TZ18N Battery

Single-walled nanotubes are dropping precipitously in price, 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.

Multi-walled

Multi-walled nanotubes (MWNT) consist of multiple rolled layers (concentric tubes) of graphite. Sony VAIO VGN-TZ190N/B Battery

There are two models that can be used to describe the structures of multi-walled nanotubes. In the Russian Doll model, sheets of graphite are arranged in concentric cylinders, e.g., a (0,8) single-walled nanotube (SWNT) within a larger (0,17) single-walled nanotube. Sony VAIO VGN-TZ190N/BC Battery

In the Parchmentmodel, a single sheet of graphite is rolled in around itself, resembling a scroll of parchment or a rolled newspaper. The interlayer distance in multi-walled nanotubes is close to the distance between graphene layers in graphite, approximately 3.4 Å. The Russian Doll structure is observed more commonly. Sony VAIO VGN-TZ191N/XC Battery

Its individual shells can be described as SWNTs, which can be metallic or semiconducting. Because of statistical probability and restrictions on the relative diameters of the individual tubes, one of the shells, and thus the whole MWNT, is usually a zero-gap metal.Sony VAIO VGN-TZ195N/XC Battery

Double-walled carbon nanotubes (DWNT) form a special class of nanotubes because their morphology and properties are similar to those of SWNT but their resistance to chemicals is significantly improved. This is especially important when functionalization is required (this means grafting of chemical functions at the surface of the nanotubes) to add new properties to the CNT.Sony VAIO VGN-TZ198N/RC Battery

In the case of SWNT, covalent functionalization will break some C=C double bonds, leaving "holes" in the structure on the nanotube and, thus, modifying both its mechanical and electrical properties. In the case of DWNT, only the outer wall is modified. DWNT synthesis on the gram-scale was first proposed in 2003 by the CCVD technique, from the selective reduction of oxide solutions in methane and hydrogen.Sony VAIO VGN-TZ250N/B Battery

The telescopic motion ability of inner shells and their unique mechanical properties permit to use multi-walled nanotubes as main movable arms in coming nanomechanical devices. Retraction force that occurs to telescopic motion caused by the Lennard-Johnes interaction between shells and it's value is about 1.5 nN.Sony VAIO VGN-TZ250N/N Battery

Torus

In theory, a nanotorus is a carbon nanotube bent into a torus (doughnut shape). Nanotori are predicted to have many unique properties, such as magnetic moments 1000 times larger than previously expected for certain specific radii. Properties such asmagnetic moment, thermal stability, etc. vary widely depending on radius of the torus and radius of the tube.Sony VAIO VGN-TZ250N/P Battery

Nanobud

Carbon nanobuds are a newly created material combining two previously discovered allotropes of carbon: carbon nanotubes and fullerenes. In this new material, fullerene-like "buds" are covalently bonded to the outer sidewalls of the underlying carbon nanotube.Sony VAIO VGN-TZ27/N Battery

This hybrid material has useful properties of both fullerenes and carbon nanotubes. In particular, they have been found to be exceptionally good field emitters. In composite materials, the attached fullerene molecules may function as molecular anchors preventing slipping of the nanotubes, thus improving the composite’s mechanical properties.Sony VAIO VGN-TZ270N/B Battery

Cup stacked carbon nanotubes

Cup-stacked carbon nanotubes (CSCNTs) differ from other quasi-1D carbon structures, which normally behave as quasi-metallic conductors of electrons. CSCNTs exhibit semiconducting behaviors due to the stacking microstructure of graphene layers.Sony VAIO VGN-TZ27N Battery

Extreme carbon nanotubes

Cycloparaphenylene

The observation of the longest carbon nanotubes (18.5 cm long) was reported in 2009. These nanotubes were grown on Si substrates using an improved chemical vapor deposition (CVD) method and represent electrically uniform arrays of single-walled carbon nanotubes.Sony VAIO VGN-TZ28/N Battery

The shortest carbon nanotube is the organic compound cycloparaphenylene, which was synthesized in early 2009.

The thinnest carbon nanotube is armchair (2,2) CNT with a diameter of 3 Å. This nanotube was grown inside a multi-walled carbon nanotube. Sony VAIO VGN-TZ285N/RC Battery

Assigning of carbon nanotube type was done by combination of high-resolution transmission electron microscopy (HRTEM),Raman spectroscopy and density functional theory (DFT) calculations.

The thinnest freestanding single-walled carbon nanotube is about 4.3 Å in diameter. Researchers suggested that it can be either (5,1) or (4,2) SWCNT, but exact type of carbon nanotube remains questionable.Sony VAIO VGN-TZ28N Battery

(3,3), (4,3) and (5,1) carbon nanotubes (all about 4 Å in diameter) were unambiguously identified using more precise aberration-corrected high-resolution transmission electron microscopy. However, they were found inside of double-walled carbon nanotubes.Sony VAIO VGN-TZ290EAB Battery

Carbon nanotubes are the strongest and stiffest materials yet discovered in terms of tensile strength and elastic modulus respectively. This strength results from the covalent sp2 bonds formed between the individual carbon atoms. In 2000, a multi-walled carbon nanotube was tested to have a tensile strength of 63 gigapascals (GPa).Sony VAIO VGN-TZ290EAN Battery

(For illustration, this translates into the ability to endure tension of a weight equivalent to 6422 kg on a cable with cross-section of 1 mm2.) Further studies, conducted in 2008, revealed that individual CNT shells have strengths of up to ~100 GPa, which is in good agreement with quantum/atomistic models.Sony VAIO VGN-TZ290EAP Battery

Since carbon nanotubes have a low density for a solid of 1.3 to 1.4 g/cm3, its specific strength of up to 48,000 kN·m·kg?1 is the best of known materials, compared to high-carbon steel's 154 kN·m·kg?1.

Under excessive tensile strain, the tubes will undergo plastic deformation, which means the deformation is permanent. Sony VAIO VGN-TZ295N/XC Battery

This deformation begins at strains of approximately 5% and can increase the maximum strain the tubes undergo before fracture by releasing strain energy.Sony VAIO VGN-TZ298N/XC Battery

Although the strength of individual CNT shells is extremely high, weak shear interactions between adjacent shells and tubes leads to significant reductions in the effective strength of multi-walled carbon nanotubes and carbon nanotube bundles down to only a few GPa’s.Sony VAIO VGN-TZ33/B Battery

This limitation has been recently addressed by applying high-energy electron irradiation, which crosslinks inner shells and tubes, and effectively increases the strength of these materials to ~60 GPa for multi-walled carbon nanotubes[19] and ~17 GPa for double-walled carbon nanotube bundles.Sony VAIO VGN-TZ33/N Battery

CNTs are not nearly as strong under compression. Because of their hollow structure and high aspect ratio, they tend to undergo buckling when placed under compressive, torsional, or bending stress.

Hardness

Standard single-walled carbon nanotubes can withstand a pressure up to 24GPa without deformation. Sony VAIO VGN-TZ33/W Battery

They then undergo a transformation to superhard phase nanotubes. Maximum pressures measured using current experimental techniques are around 55GPa. However, these new superhard phase nanotubes collapse at an even higher, albeit unknown, pressure.

The bulk modulus of superhard phase nanotubes is 462 to 546 GPa, even higher than that of diamond(420 GPa for single diamond crystal). Sony VAIO VGN-TZ350N/B Battery

Kinetic

Multi-walled nanotubes are multiple concentric nanotubes precisely nested within one another. These exhibit a striking telescoping property whereby an inner nanotube core may slide, almost without friction, within its outer nanotube shell, thus creating an atomically perfect linear or rotational bearing. Sony VAIO VGN-TZ350N/N Battery

This is one of the first true examples of molecular nanotechnology, the precise positioning of atoms to create useful machines. Already, this property has been utilized to create the world's smallest rotational motor. Future applications such as a gigahertz mechanical oscillator are also envisaged.Sony VAIO VGN-TZ350N/P Battery

Electrical

Because of the symmetry and unique electronic structure of graphene, the structure of a nanotube strongly affects its electrical properties. For a given (n,m) nanotube, if n = m, the nanotube is metallic; if n ? m is a multiple of 3, then the nanotube is semiconducting with a very small band gap, otherwise the nanotube is a moderate semiconductor. Sony VAIO VGN-TZ370N/B Battery

Thus all armchair (n = m) nanotubes are metallic, and nanotubes (6,4), (9,1), etc. are semiconducting.

However, this rule has exceptions, because curvature effects in small diameter carbon nanotubes can strongly influence electrical properties. Thus, a (5,0) SWCNT that should be semiconducting in fact is metallic according to the calculations. Sony VAIO VGN-TZ37N/G Battery

Likewise, vice versa-- zigzag and chiral SWCNTs with small diameters that should be metallic have finite gap (armchair nanotubes remain metallic).In theory, metallic nanotubes can carry an electric current density of 4 × 109 A/cm2, which is more than 1,000 times greater than those of metals such as copper, where for copper interconnects current densities are limited byelectromigration.Sony VAIO VGN-TZ37N/P Battery

Multiwalled carbon nanotubes with interconnected inner shells show superconductivity with a relatively high transition temperature Tc = 12 K. In contrast, the Tc value is an order of magnitude lower for ropes of single-walled carbon nanotubes or for MWNTs with usual, non-interconnected shells.Sony VAIO VGN-TZ37N/R Battery

All nanotubes are expected to be very good thermal conductors along the tube, exhibiting a property known as "ballistic conduction", but good insulators laterally to the tube axis. Measurements show that a SWNT has a room-temperature thermal conductivity along its axis of about 3500 W·m?1·K?1;Sony VAIO VGN-TZ37N/X Battery

compare this to copper, a metal well known for its good thermal conductivity, which transmits 385 W·m?1·K?1. A SWNT has a room-temperature thermal conductivity across its axis (in the radial direction) of about 1.52 W·m?1·K?1,which is about as thermally conductive as soil. Sony VAIO VGN-TZ38N/X Battery

The temperature stability of carbon nanotubes is estimated to be up to 2800 °C in vacuum and about 750 °C in air.

Defects

As with any material, the existence of a crystallographic defect affects the material properties. Defects can occur in the form of atomic vacancies. High levels of such defects can lower the tensile strength by up to 85%. Sony VAIO VGN-TZ398U/XC Battery

An important example is the Stone Wales defect, which creates a pentagon and heptagon pair by rearrangement of the bonds. Because of the very small structure of CNTs, the tensile strength of the tube is dependent on its weakest segment in a similar manner to a chain, where the strength of the weakest link becomes the maximum strength of the chain.Sony VAIO VGN-TZ50B Battery

Crystallographic defects also affect the tube's electrical properties. A common result is lowered conductivity through the defective region of the tube. A defect in armchair-type tubes (which can conduct electricity) can cause the surrounding region to become semiconducting, and single monoatomic vacancies induce magnetic properties.Sony VAIO VGN-TZ90HS Battery

Crystallographic defects strongly affect the tube's thermal properties. Such defects lead to phonon scattering, which in turn increases the relaxation rate of the phonons. This reduces the mean free path and reduces the thermal conductivity of nanotube structures.Sony VAIO VGN-TZ90NS Battery

Phonon transport simulations indicate that substitutional defects such as nitrogen or boron will primarily lead to scattering of high-frequency optical phonons. However, larger-scale defects such as Stone Wales defectscause phonon scattering over a wide range of frequencies, leading to a greater reduction in thermal conductivity. Sony VAIO VGN-TZ90S Battery

One-dimensional transport

Because of the nanoscale dimensions, electrons propagate only along the tube's axis and electron transport involves many quantum effects. Because of this, carbon nanotubes are frequently referred to as “one-dimensional”.

Toxicity

The toxicity of carbon nanotubes has been an important question in nanotechnology. Sony VAIO VPC CW2MFX/PU Battery

Such research has just begun. The data are still fragmentary and subject to criticism. Preliminary results highlight the difficulties in evaluating the toxicity of this heterogeneous material. Parameters such as structure, size distribution,surface area, surface chemistry, surface charge, and agglomeration state as well as purity of the samples, have considerable impact on the reactivity of carbon nanotubes.Sony VAIO VPC S11V9E/B Battery

However, available data clearly show that, under some conditions, nanotubes can cross membrane barriers, which suggests that, if raw materials reach the organs, they can induce harmful effects such as inflammatory and fibrotic reactions.

A study led by Alexandra Porter from the University of Cambridge shows that CNTs can enter human cells and accumulate in the cytoplasm, causing cell death.Sony VAIO VPCB119GJ/B Battery

Results of rodent studies collectively show that regardless of the process by which CNTs were synthesized and the types and amounts of metals they contained, CNTs were capable of producing inflammation, epithelioid granulomas (microscopic nodules), fibrosis, and biochemical/toxicological changes in the lungs.Sony VAIO VPCB11AGJ Battery

Comparative toxicity studies in which mice were given equal weights of test materials showed that SWCNTs were more toxic than quartz, which is considered a serious occupational health hazard when chronically inhaled. As a control, ultrafine carbon black was shown to produce minimal lung responses.Sony VAIO VPCB11AVJ Battery

The needle-like fiber shape of CNTs is similar to asbestos fibers. This raises the idea that widespread use of carbon nanotubes may lead to pleural mesothelioma, a cancer of the lining of the lungs or peritoneal mesothelioma, a cancer of the lining of the abdomen (both caused by exposure to asbestos). Sony VAIO VPCB11V9E Battery

A recently-published pilot study supports this prediction. Scientists exposed the mesothelial lining of the body cavity of mice to long multiwalled carbon nanotubes and observed asbestos-like, length-dependent, pathogenic behavior that included inflammation and formation of lesions known as granulomas. Authors of the study conclude:Sony VAIO VPCB11X9E Battery

"This is of considerable importance, because research and business communities continue to invest heavily in carbon nanotubes for a wide range of products under the assumption that they are no more hazardous than graphite. Our results suggest the need for further research and great caution before introducing such products into the market if long-term harm is to be avoided."Sony VAIO VPCCW18FJ/P Battery

According to co-author Dr. Andrew Maynard:

"This study is exactly the kind of strategic, highly focused research needed to ensure the safe and responsible development of nanotechnology. It looks at a specific nanoscale material expected to have widespread commercial applications and asks specific questions about a specific health hazard.Sony VAIO VPCCW18FJ/R Battery

Even though scientists have been raising concerns about the safety of long, thin carbon nanotubes for over a decade, none of the research needs in the current U.S. federal nanotechnology environment, health and safety risk research strategy address this question." Sony VAIO VPCCW18FJ/W Battery

Although further research is required, the available data suggests that under certain conditions, especially those involving chronic exposure, carbon nanotubes can pose a serious risk to human health.

Synthesis

Techniques have been developed to produce nanotubes in sizeable quantities, including arc discharge, laser ablation, high pressure carbon monoxide (HiPco), and chemical vapor deposition (CVD).Sony VAIO VPCCW19FJ/W Battery

Most of these processes take place in vacuum or with process gases. CVD growth of CNTs can occur in vacuum or at atmospheric pressure. Large quantities of nanotubes can be synthesized by these methods; advances in catalysis and continuous growth processes are making CNTs more commercially viable.Sony VAIO VPCCW1AFJ Battery

Arc discharge

Nanotubes were observed in 1991 in the carbon soot of graphite electrodes during an arc discharge, by using a current of 100 amps, that was intended to produce fullerenes. However the first macroscopic production of carbon nanotubes was made in 1992 by two researchers at NEC's Fundamental Research Laboratory.Sony VAIO VPCCW1AHJ Battery

The method used was the same as in 1991. During this process, the carbon contained in the negative electrode sublimates because of the high discharge temperatures. Because nanotubes were initially discovered using this technique, it has been the most widely-used method of nanotube synthesis.Sony VAIO VPCCW1S1E Battery

The yield for this method is up to 30% by weight and it produces both single- and multi-walled nanotubes with lengths of up to 50 micrometers with few structural defects.

Laser ablation

In the laser ablation process, a pulsed laser vaporizes a graphite target in a high-temperature reactor while an inert gas is bled into the chamber. Sony VAIO VPCCW1S1E/B Battery

Nanotubes develop on the cooler surfaces of the reactor as the vaporized carbon condenses. A water-cooled surface may be included in the system to collect the nanotubes.

This process was developed by Dr. Richard Smalley and co-workers at Rice University, who at the time of the discovery of carbon nanotubes, were blasting metals with a laser to produce various metal molecules. Sony VAIO VPCCW1S1E/L Battery

When they heard of the existence of nanotubes they replaced the metals with graphite to create multi-walled carbon nanotubes. Later that year the team used a composite of graphite and metal catalyst particles (the best yield was from a cobalt and nickel mixture) to synthesize single-walled carbon nanotubes.Sony VAIO VPCCW1S1E/P Battery

The laser ablation method yields around 70% and produces primarily single-walled carbon nanotubes with a controllable diameter determined by the reactiontemperature. However, it is more expensive than either arc discharge or chemical vapor deposition.Sony VAIO VPCCW1S1E/R Battery

Chemical vapor deposition (CVD)

The catalytic vapor phase deposition of carbon was first reported in 1959, but it was not until 1993 that carbon nanotubes were formed by this process. In 2007, researchers at the University of Cincinnati (UC) developed a process to grow aligned carbon nanotube arrays of 18 mm length on a FirstNano ET3000 carbon nanotube growth system.Sony VAIO VPCCW21FX/B Battery

During CVD, a substrate is prepared with a layer of metal catalyst particles, most commonly nickel, cobalt, iron, or a combination. The metal nanoparticles can also be produced by other ways, including reduction of oxides or oxides solid solutions. The diameters of the nanotubes that are to be grown are related to the size of the metal particles. Sony VAIO VPCCW21FX/L Battery

This can be controlled by patterned (or masked) deposition of the metal, annealing, or by plasma etching of a metal layer. The substrate is heated to approximately 700°C. To initiate the growth of nanotubes, two gases are bled into the reactor: a process gas (such asammonia, nitrogen or hydrogen) and a carbon-containing gas (such as acetylene, ethylene, ethanol or methane).Sony VAIO VPCCW21FX/R Battery

Nanotubes grow at the sites of the metal catalyst; the carbon-containing gas is broken apart at the surface of the catalyst particle, and the carbon is transported to the edges of the particle, where it forms the nanotubes. This mechanism is still being studied. The catalyst particles can stay at the tips of the growing nanotube during the growth process, or remain at the nanotube base, depending on the adhesion between the catalyst particle and the substrate. Sony VAIO VPCCW21FX/W Battery

Thermal catalytic decomposition of hydrocarbon has become an active area of research and can be a promising route for the bulk production of CNTs. Fluidised bed reactor is the most widely used reactor for CNT preparation. Scale-up of the reactor is the major challenge.Sony VAIO VPCCW26EC Battery

CVD is a common method for the commercial production of carbon nanotubes. For this purpose, the metal nanoparticles are mixed with a catalyst support such as MgO or Al2O3 to increase the surface area for higher yield of the catalytic reaction of the carbon feedstock with the metal particles. Sony VAIO VPCCW26FX/B Battery

One issue in this synthesis route is the removal of the catalyst support via an acid treatment, which sometimes could destroy the original structure of the carbon nanotubes. However, alternative catalyst supports that are soluble in water have proven effective for nanotube growth.Sony VAIO VPCCW28EC Battery

If a plasma is generated by the application of a strong electric field during the growth process (plasma enhanced chemical vapor deposition), then the nanotube growth will follow the direction of the electric field. By adjusting the geometry of the reactor it is possible to synthesize vertically aligned carbon nanotubes (i.e., perpendicular to the substrate), Sony VAIO VPCCW28FJ/P Battery

a morphology that has been of interest to researchers interested in the electron emission from nanotubes. Without the plasma, the resulting nanotubes are often randomly oriented. Under certain reaction conditions, even in the absence of a plasma, closely spaced nanotubes will maintain a vertical growth direction resulting in a dense array of tubes resembling a carpet or forest.Sony VAIO VPCCW28FJ/R Battery

Of the various means for nanotube synthesis, CVD shows the most promise for industrial-scale deposition, because of its price/unit ratio, and because CVD is capable of growing nanotubes directly on a desired substrate, whereas the nanotubes must be collected in the other growth techniques. The growth sites are controllable by careful deposition of the catalyst.Sony VAIO VPCCW28FJ/W Battery

In 2007, a team from Meijo University demonstrated a high-efficiency CVD technique for growing carbon nanotubes from camphor. Researchers at Rice University, until recently led by the late Richard Smalley, have concentrated upon finding methods to produce large, pure amounts of particular types of nanotubes. Sony VAIO VPCCW29FJ/W Battery

Their approach grows long fibers from many small seeds cut from a single nanotube; all of the resulting fibers were found to be of the same diameter as the original nanotube and are expected to be of the same type as the original nanotube.

Super-growth CVD

Super-growth CVD (water-assisted chemical vapor deposition) process was developed by Kenji Hata, Sumio Iijima and co-workers at AIST, Japan.Sony VAIO VPCCW2AFJ Battery

In this process, the activity and lifetime of the catalyst are enhanced by addition of water into the CVD reactor. Dense millimeter-tall nanotube "forests", aligned normal to the substrate, were produced. The forests growth rate could be expressed, as

In this equation, ? is the initial growth rate and ?o is the characteristic catalyst lifetime.Sony VAIO VPCCW2AHJ Battery

Their specific surface exceeds 1,000 m2/g (capped) or 2,200 m2/g (uncapped), surpassing the value of 400–1,000 m2/g for HiPco samples. The synthesis efficiency is about 100 times higher than for the laser ablation method. The time required to make SWNT forests of the height of 2.5 mm by this method was 10 minutes in 2004.Sony VAIO VPCCW2S1E Battery

Those SWNT forests can be easily separated from the catalyst, yielding clean SWNT material (purity >99.98%) without further purification. For comparison, the as-grown HiPco CNTs contain about 5–35% of metal impurities; it is therefore purified through dispersion and centrifugation that damages the nanotubes. Sony VAIO VPCCW2S1E/B Battery

The super-growth process avoids this problem. Patterned highly organized single-walled nanotube structures were successfully fabricated using the super-growth technique.

The mass density of super-growth CNTs is about 0.037 g/cm3. It is much lower than that of conventional CNT powders (~1.34 g/cm3), probably because the latter contain metals and amorphous carbon.Sony VAIO VPCCW2S1E/L Battery

The super-growth method is basically a variation of CVD. Therefore, it is possible to grow material containing SWNT, DWNTs and MWNTs, and to alter their ratios by tuning the growth conditions. Their ratios change by the thinness of the catalyst. Many MWNTs are included so that the diameter of the tube is wide.Sony VAIO VPCCW2S1E/P Battery

The vertically aligned nanotube forests originate from a "zipping effect" when they are immersed in a solvent and dried. The zipping effect is caused by the surface tension of the solvent and the van der Waals forces between the carbon nanotubes. It aligns the nanotubes into a dense material, which can be formed in various shapes, such as sheets and bars, Sony VAIO VPCCW2S1E/R Battery

by applying weak compression during the process. Densification increases the Vickers hardness by about 70 times and density is 0.55 g/cm3. The packed carbon nanotubes are more than 1 mm long and have a carbon purity of 99.9% or higher; they also retain the desirable alignment properties of the nanotubes forest.Sony VAIO VPCCW2S1E/W Battery

Natural, incidental, and controlled flame environments

Fullerenes and carbon nanotubes are not necessarily products of high-tech laboratories; they are commonly formed in such mundane places as ordinary flames, produced by burning methane, ethylene, and benzene,and they have been found in soot from both indoor and outdoor air.Sony VAIO VPCCW2S5C CN1 Battery

However, these naturally occurring varieties can be highly irregular in size and quality because the environment in which they are produced is often highly uncontrolled. Thus, although they can be used in some applications, they can lack in the high degree of uniformity necessary to satisfy the many needs of both research and industry.Sony VAIO VPCF112FX/B Battery

Recent efforts have focused on producing more uniform carbon nanotubes in controlled flame environments.Such methods have promise for large-scale, low-cost nanotube synthesis, though they must compete with rapidly developing large scale CVD production.Sony VAIO VPCF115FG/B Battery,Sony VAIO VPCF116FGBI Battery,Sony VAIO VPCF117FJ/W Battery,Sony VAIO VPCF117HG/BI Battery,Sony VAIO VPCF118FJ/W Battery,Sony VAIO VPCF119FC Battery