Thermal Conductivity of Two Types of 2D Carbon Allotropes ...
Allotropes of carbon
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COORDINATE COVALENT
• Coordinate covalent bond • -a covalent bond in which one atom
contributes both electrons• -once such bond is formed we cannot tell it
from regular covalent bond• Example: HCl + NH3 forms NH4Cl
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METALLIC BONDS
• -Electron Sea Model• -pictures a solid metal as a network of positive
ions immersed in “sea of electrons”• -electrons in the sea are free (not attached to
any particular ion) and they are mobile.
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NETWORK COVALENT SOLIDS
• Solids in which all the atoms are Bonded covalently.
Properties:• Very hard• Very high mp• Poor thermal and electrical conductorsExample: C (diamond)
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Allotropes of Carbon
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Allotropes of Carbon
• Diamond is one of the best known allotropes of carbon.
• useful for both industrial applications and jewelry.
• hardest known natural mineral.
• dominant industrial use is in cutting, drilling, grinding (diamond edged cutters), and polishing.
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Allotropes of Carbon• Graphite- (graphein, "to
draw/write", for its use in pencils).
• Unlike diamond, graphite is an electrical conductor.
• the most stable form of carbon.
• Graphite powder is used as a dry lubricant.
• A single layer of graphite is called graphene.
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Allotropes of Carbon• Amorphous carbon -
carbon that does not have any crystalline structure.
• some short-range order can be observed, but there is no long-range pattern of atomic positions..
• Coal and soot or carbon black are informally called amorphous carbon.
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Allotropes of Carbon
• Coal• is a sought-after energy
source. It has the largest reserve and is often the cheapest of the fuel options.
• fossil fuel created from the remains of plants that lived and
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Allotropes of Carbon
• Soot- also known as black carbon, is the second-leading cause of global warming after carbon dioxide
• a black, carbonaceous substance produced during incomplete combustion of coal, wood, oil, etc.
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Allotropes of Carbon• Fullerenes-
buckminsterfullerenes, or usually just fullerenes or buckyballs for short.
• are molecules of varying sizes composed entirely of carbon, which take the form of a hollow sphere, ellipsoid, or tube
• were under study for potential medicinal use — binding specific antibiotics to the structure to target resistant bacteria and even target certain cancer cells such as melanoma.
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Allotropes of Carbon• Carbon nanotubes- also
called buckytubes• are cylindrical carbon
molecules with novel properties
• (e.g., nano-electronics, optics, materials applications, etc.)
• a member of the fullerene structural family, which also includes buckyballs.
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Allotropes of Carbon• Glassy carbon or vitreous
carbon is a class of non-graphitizing carbon
• widely used as an electrode material in electrochemistry, as well as for high temperature crucibles and as a component of some prosthetic devices
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Allotropes of Carbon• Carbon nanofoam -
consists of a low-density cluster-assembly of carbon atoms strung together in a loose three-dimensional web
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Allotropes of Carbon• Carbon nanobuds
newly discovered allotrope of carbon in which fullerene like "buds" are covalently attached to the outer sidewalls of the carbon nanotubes.
• has useful properties of both fullerenes and carbon nanotubes
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Allotropes of Carbon
• Lonsdaleite -hexagonal allotrope of the carbon allotrope diamond
• believed to form from graphite present in meteorites upon their impact to Earth.
• diamond but retains graphite's hexagonal crystal lattice