Diamonds
Chemistry of Diamond:
Properties & Types
PROPERTIES OF DIAMONDS
Diamond is the hardest natural material.
The Mohs hardness scale, on which diamond is a '10' and corundum (sapphire) is a '9', doesn't adequately attest to this incredible hardness, as diamond is exponentially harder than corundum.
Diamond is also the least compressible and stiffest substance.
It is an exceptional thermal conductor - 4 times better than copper - which gives significance to diamonds being called 'ice'.
Diamond has an extremely low thermal expansion, is chemically inert with respect to most acids and alkalis, is transparent from the far infrared through the deep ultraviolet, and is one of only a few materials with a negative work function (electron affinity).
One consequence of the negative electron affinity is that diamonds repel water, but readily accept hydrocarbons such as wax or grease.
Diamonds do not conduct electricity well, although some are semiconductors.
Diamonds can burn if subjected to a high temperature in the presence of oxygen.
Diamond has a high specific gravity; it is amazingly dense given the low atomic weight of carbon.
The brilliance and fire of a diamond are due to its high dispersion and high refractive index.
Diamond has the highest reflectance and index of refraction of any transparent substances.
Diamond gemstones are commonly clear or pale blue, but colored diamonds, called 'fancies,’ have been found in all the colors of the rainbow.
Boron, which lends a bluish color, and nitrogen, which adds a yellow cast, are common trace impurities.
Two volcanic rocks that may contain diamonds are kimberlite and lamproite.
Diamond crystals frequently contain inclusions of other minerals, such as garnet or chromite.
Many diamonds fluoresce blue to violet, sometimes strongly enough to be seen in daylight.
Some blue-fluorescing diamonds phosphoresce yellow (glow in the dark in an afterglow reaction).
TYPE OF DIAMONDS
Natural Diamonds
Natural diamonds are classified by the type and quantity of impurities found within them.
· Type Ia - This is the most common type of natural diamond, containing up to 0.3% nitrogen.
· Type Ib - Very few natural diamonds are this type (~0.1%), but nearly all synthetic industrial diamonds are. Type Ib diamonds contain up to 500 ppm nitrogen.
· Type IIa - This type is very rare in nature. Type IIa diamonds contain so little nitrogen that it isn't readily detected using infrared or ultraviolet absorption methods.
· Type IIb - This type is also very rare in nature. Type IIb diamonds contain so little nitrogen (even lower than type IIa) that the crystal is a p-type semiconductor.
Synthetic Industrial Diamonds
Synthetic industrial diamonds have produced the process of High-Pressure High-Temperature Synthesis (HPHT).
In HPHT synthesis, graphite and a metallic catalyst are placed in a hydraulic press under high temperatures and pressures.
Over the period of a few hours, the graphite converts to diamond. The resulting diamonds are usually a few millimeters in size and too flawed for use as gemstones, but they are extremely useful as edges on cutting tools and drill bits and for being compressed to generate very high pressures.
(Interesting side note: Although used to cut, grind, and polish many materials, diamonds aren't used to machine alloys of iron because the diamond abrades very quickly, due to a high-temperature reaction between iron and carbon.)
Thin Film Diamonds
A process called Chemical Vapor Deposition (CVD) may be used to deposit thin films of polycrystalline diamond.
CVD technology makes it possible to put 'zero-wear' coatings on machine parts, use diamond coatings to draw the heat away from electronic components, fashion windows that are transparent over a broad wavelength range, and take advantage of other properties of diamonds.
ANNE MARIE HELMENSTINE, PH.D.
Anne Helmenstine, Ph.D., is an author and consultant with a broad scientific and medical background.
EXPERIENCE
Anne has taught chemistry, biology, and physics at the high school, college, and graduate level. In her doctoral work, Anne developed ultra-sensitive chemical detection and medical diagnostic tests. She has worked abstracting/indexing diverse scientific literature for the Department of Energy. She presently works as a freelance writer and scientific consultant. She enjoys adapting lab-based science projects so that they can be performed safely at home.
EDUCATION
Dr. Helmenstine has bachelor of arts degrees in physics and mathematics with a minor in chemistry from Hastings College in Nebraska and a doctorate of philosophy in biomedical sciences from the University of Tennessee at Knoxville.
Chemistry is part of everyone's life, from cooking and cleaning to the latest computer chip technology and vaccine development. It doesn't have to be intimidating and it doesn't have to be hard to understand.
You can read more about Anne's current and past work on her Google Profile: Anne Helmenstine. Find Anne's printable periodic tables and science projects at Science Notes.
You may also like:
CLICK HERE:
CLICK HERE:
CLICK HERE:
CLICK HERE:
CLICK HERE:
.
Multi-Media Filter, Highly-Activated Carbon Filter,
Zeolite-Process Water Softener With Brine Tank,
Fiberglass Ballast-Type Pressure Tank
(fully automatic backwash & regeneration)
PURICARE
Systems
...
 |
| Multi-Media Filter, Highly-Activated Carbon Filter, Zeolite-Process Water Softener With Brine Tank, Fiberglass Ballast-Type Pressure Tank (fully automatic backwash & regeneration) |
PURICARE
Water
Treatment
Systems
.
...
...
Aganan, Pavia, Iloilo, Philippines
...
CLICK HERE . . . to view company profile . . .
Aganan, Pavia, Iloilo, Philippines
...
CLICK HERE . . . to view company profile . . .
CLICK HERE . . . to view company profile . . .
 |
| Ballast-TypePressure Tank |
 |
| Houston Water Pump with Mazaki Automatic Pump Controller |
No comments:
Post a Comment