| Diamond
tools for drilling, sawing, grinding and
shaping are still the main applications of
industrial diamond and are all based on the
extreme hardness of diamond, the most
commonly known property of this material.
However diamond offers a unique combination
of optical, thermal, mechanical, chemical
and electrical properties. |
| |
| Mechanical
properties: Diamond is the
hardest known material and has one of the
lowest coefficients of friction ensuring a
wide range of applications in cutting tools
and wear resistant parts. The hardness and
wear resistance is also an important asset
in optical and other applications where the
components are exposed to erosive
environments. |
| |
| Chemical
properties: Diamond is an
extremely inert material, and is highly
resistant to chemical attack. It offers
protection to most severe corrosive
environments. |
| |
| Electrical
properties: Due to its large band
gap and purity, diamond is an excellent
electrical insulator. |
| |
| The
uniqueness of
diamond as an engineering
material for thermal, optical and cutting
applications is based on specific
combinations of the above described
properties. |
| |
| Thermal properties: The thermal conductivity of diamond at room temperature is the highest of all known materials. It is a factor of five times greater than copper and over a factor of ten larger than commonly used thermally conductive electrical insulators such as aluminium nitride or beryllium oxide. Due to its relatively low specific heat capacity, diamond excels as a heat diffuser in transient applications in which the speed of heat transfer is important. Diamond also exhibits a low coefficient of thermal expansion which enhances the resistance to thermal shock. |
| |
| Optical properties: Diamond is transparent to electromagnetic radiation over a very wide spectral range, from 220nm wavelength in the ultra-violet to the far infrared and over most of the microwave radar frequencies except for an intrinsic phonon band in the 3 to 5 micron (Type 2a) wavelength range. The wide spectral range of optical transparency is unique among all the optical materials, |
|
|
| Properties
of Natural Diamond |
| |
| I. Classification: |
| |
| Diamond can be divided into the following classifications: |
| |
| Type Ia diamond: |
| Contains nitrogen as an impurity in fairly substantial amounts (of the order of 0.1%), and which appears to have segregated into small aggregates. Also contains platelets, associated with the nitrogen impurity, the exact structure of which is not known.
It has an absorption edge at ~300nm and a broad absorption band between 7 and 10µm.
Most natural diamonds are of this type. |
|
| Type Ib diamond: |
| Also contains nitrogen as an impurity but in dispersed substitutional form. Almost all synthetic diamonds are of this type. |
|
| Type IIa diamond: |
| Effectively free of nitrogen impurity. Very rare in nature, these diamonds have enhanced optical and thermal properties.
The high purity results in an ultraviolet transmission band down to approximate 230µm and absence of infrared absorption in the 7-10µm band. |
|
| Type IIb diamond: |
| A very pure type of diamond which has semiconducting properties: generally blue in color. Extremely rare in nature. |
|
| |
| II.
Physical
Properties
|
| |
Refractive Index @ 546.1nm
|
|
2.4237 |
Type IIa Absorption coefficient
@ 10.6µm (cm-1)
|
|
0.03-0.035 |
Type IIa Transmission @10.6µm
|
|
> 71% |
Knoop Hardness (kg/mm2) (111)
surface
|
|
9000 |
Young's modulus
|
: |
10.50 1011N/m2 |
Poisson's ratio
|
: |
0.104 |
Thermal Conductivity @ 293K
Type IA
Type IIA |
|
600-1000 W/mK
2000-2100 W/mK |
Thermal expansion coefficient
@ 293K |
|
0.8 ± 0.1 x 10-6 |
| Density
(103
kg/m3) |
: |
3.515 ± 0.0005 |
Specific heat capacity
@ 300K (J/mol K) |
|
6.195 |
|
|
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