Diamond transforms to graphite when heated at 2000℃ in vacuum and transforms to CO2 at
710–900℃ in air.
The space lattice of a diamond belongs to the cubic system, and its diamond structure has a lattice
constant of a=0.3560 nm and a cleavage plane of 111.
Diamond is classified optically as Type I and Type II. Type I shows the absorption bands at 8
and 20.8 mm by the impurities other than the 5 mm absorption band. On the other hand, Type II
shows the 5 mm absorption band only.
The transmittance of Type II is T=60% for wavelengths longer than 6 mm. There is no other
material that shows such an optical property.
Diamond is excellent as a transmission window because it has no absorption in the infrared and farinfrared region. However, large diamond pieces are difficult to obtain, and they are used as a special
window (i.e., a window of a Golay cell).
diamond: The hardest known mineral(with a hardness of 10 on Mohs’scale). It is an allotropic form of purecarbon that has crystallized in thecubic system, usually as octahedra orcubes, under great pressure. Diamondcrystals may be colourless andtransparent or yellow, brown, orblack. They are highly prized as gemstonesbut also have extensive usesin industry, mainly for cutting andgrinding tools. Diamonds occur in ancientvolcanic pipes of kimberlite;the most important deposits are inSouth Africa but others are found inTanzania, the USA, Russia, and Australia.Diamonds also occur in riverdeposits that have been derived fromweathered kimberlite, notably inBrazil, Za?re, Sierra Leone, and India.Industrial diamonds are increasinglybeing produced synthetically.
An allotrope of CARBON. It is the
hardest naturally occurring substance and
is used for jewelry and, industrially, for
cutting and drilling equipment. Each carbon
atom is surrounded by four equally
spaced carbon atoms arranged tetrahedrally.
The carbon atoms form a three-dimensional
network with each
carbon–carbon bond equal to 0.154 nm
and at an angle of 109.5° with its neighbors.
In diamonds millions of atoms are covalently
bonded to form a giant molecular
structure, the great strength of which results
from the strong covalent bonds. Diamonds
can be formed synthetically from
graphite in the presence of a catalyst and
under extreme temperature and pressure;
although small, such diamonds are of adequate
size for many industrial uses.
Diamond is produced with so called, diamond luster, and is white or transparent. But sometimes
yellow, red, orange, green, blue, brown, and black colored diamond exists. Black diamond is called
carbonad. The diamond from Kimberley, a major mining source, is called Kimberlite. Recently,
diamond has been fabricated under high temperature and pressure, but it is not as large and is used
only for abrasives.
Diamond is the cubic crystalline form of carbon.When pure, diamond is water clear, butimpurities add shades of opaqueness including black. It is the hardest natural material with ahardness on the Knoop scale ranging from 5500to 7000. It will scratch and be scratched by thehardest anthropogenic material Borozon. It hasa specific gravity of 3.5. Diamond has a meltingpoint of around 3871°C, at which point it willgraphitize and then vaporize. Diamonds aregenerally electrical insulators and nonmagnetic.Synthetic diamonds are produced from graphiteat extremely high pressures (5444 to 12,359.9MPa) and temperatures from 1204 to 2427°C.They are up to 0.01 carat in size and are comparableto the quality of industrial diamonds.In powder form they are used in cutting wheels.Of all diamonds mined, about 80% by weightare used in industry. Roughly 45% of the totalindustrial use is in grinding wheels. Tests haveshown that under many conditions syntheticdiamonds are better than mined diamonds inthis application.
