Jul 11 2013
Topics Covered
Introduction
Chemical Properties
Physical Properties
Mechanical Properties
Thermal Properties
Applications
Introduction
Molybdenum is a chemical element with Mo as its symbol. It belongs to group 6 and periodic 5 of the periodic table. Its atomic number is 42, and has a Mohs hardness of 5.5.
Molybdenum can be obtained from the minerals molybdenite, wulfenite and powellite. It is also obtained as a byproduct during tungsten and copper mining and processing. It has one of the highest melting points of all pure elements; however it is not resistant to acids.
The main molybdenum mining areas are USA, Canada, Chile, and Russia.
Chemical Properties
The chemical properties of molybdenum are provided in the table below.
Chemical Data
|
CAS number |
7439-98-7 |
|
Thermal neutron cross section |
2.5 barns/atom |
|
Electrode potential |
-0.200 V |
|
Ionic radius |
0.620 Å |
|
Electronegativity |
2.16 |
|
X-ray absorption edge |
0.61977 Å |
|
Electrochemical equivalent |
1.79 g/A/h |
Physical Properties
The following table discusses the physical properties of molybdenum.
|
Properties |
Metric |
Imperial |
|
Density |
10.22 g/cm3 |
0.3692 lb/in3 |
|
Melting point |
2610 °C |
4730°F |
|
Boiling point |
4825 °C |
8717°F |
Mechanical Properties
The mechanical properties of molybdenum are tabulated below.
|
Properties |
Metric |
Imperial |
|
Tensile strength |
324 MPa |
47000 psi |
|
Poisson’s ratio |
0.38 |
0.38 |
|
Modulus of elasticity |
330 GPa |
47900 ksi |
|
Shear modulus |
120 GPa |
17400 ksi |
|
Hardness, Brinell |
225 |
225 |
|
Hardness, Vickers |
230 |
230 |
|
Hardness, Rockwell A |
60 |
60 |
|
Hardness, Rockwell B |
98 |
98 |
|
Hardness, Rockwell C |
19 |
19 |
Thermal Properties
The thermal properties of molybdenum are tabulated below.
|
Properties |
Metric |
Imperial |
|
Thermal expansion co-efficient (@20°C/68°F) |
5.35 µm/m°C |
2.97 µin/in°F |
|
Thermal conductivity |
138 W/mK |
958 BTU in/hr.ft².°F |
Applications
The following are the application areas of molybdenum:
-
As an alloying agent to provide hardness and toughness to quenched/tempered steels, and to improve the strength of steels at high temperatures
-
As electrodes for electrically heated glass furnaces and forehearths
-
In nuclear energy applications
-
As missile and aircraft parts requiring high temperature resistance
-
As a catalyst in petroleum refining
-
As a filament material in electronic/electrical applications
-
Flame- and corrosion-resistant coatings for other metals
-
As a support member in radio and light bulbs
-
In arc resistant electric contacts
-
In thermocouple sheaths
Molybdenum can be formed into many useful compounds. Some are listed below with their specific application areas:
-
Molybdenum sulfide and selenites - as a high temperature lubricant in favor to petroleum based oils, due to its superior high temperature resistance.
-
Sodium molybdate (anhydrous form) - as a dry powdered fertilizer