Aug 13 2013
Topics Covered
Introduction
Chemical Properties
Physical Properties
Mechanical Properties
Thermal Properties
Applications
Introduction
Iridium is a chemical element with ‘Ir’ as its symbol. It belongs to group 9 of the periodic table and its atomic number is 77.
Iridium, palladium, platinum, ruthenium, rhodium, and osmium are a group of elements that are referred to as the platinum group metals (PGM).
Iridium is silvery white in color and is the most corrosion-resistant metal known. It can be obtained from platinum ores and as a by-product of mining nickel. It has a face centered cubic structure. This metal is very hard and brittle and hence quite difficult to machine and work. It remains unaffected by air, water and acids.
Chemical Properties
The chemical properties of iridium are provided in the table below.
|
Chemical Data |
|
CAS number |
7439-88-5 |
|
Thermal neutron cross section |
440 barns/atom |
|
Electrode potential |
1.0 V |
|
Ionic radius |
0.680 Å |
|
Electronegativity |
2.2 |
|
X-ray absorption edge |
0.16286 Å |
Physical Properties
The following table discusses the physical properties of iridium.
|
Properties |
Metric |
Imperial |
|
Density |
22.65 g/cm3 |
0.8183 lb/in3 |
|
Melting point |
2450 °C |
4442°F |
|
Boiling point |
4527 °C |
8181°F |
Mechanical Properties
The mechanical properties of iridium are tabulated below.
|
Properties |
Metric |
Imperial |
|
Tensile strength |
2000 MPa |
290000 psi |
|
Poisson’s ratio |
0.26 |
0.26 |
|
Modulus of elasticity |
524 GPa |
76000 ksi |
|
Shear modulus |
208 GPa |
30200 ksi |
|
Hardness, Brinell |
565 |
565 |
|
Hardness, Vickers |
650 |
650 |
|
Hardness, Rockwell A |
80 |
80 |
|
Hardness, Rockwell C |
56 |
56 |
Thermal Properties
The thermal properties of iridium are tabulated below.
|
Properties |
Metric |
Imperial |
|
Thermal expansion co-efficient (@20-100°C/68-212°F) |
6.80 µm/m°C |
3.78 µin/in°F |
|
Thermal conductivity |
147 W/mK |
1020 BTU in/hr.ft².°F |
Applications
Iridium is mainly consumed by the automotive, electronic, and chemical industries.
The following are the other application areas of iridium:
-
In alloys
-
Pivot bearings
-
In tipping fountain pen nibs
-
for compass bearings
-
In scientific and other special equipment
-
Long-life aircraft engine parts are made of an iridium alloy