Hafnium (Hf) – Properties, Applications

Topics Covered

Introduction
Chemical Properties
Physical Properties
Mechanical Properties
Thermal Properties
Applications

Introduction

Hafnium is a chemical element with Hf as its symbol. It belongs to group 4, periodic number 6 of the periodic table. Its atomic number is 72.

Hafnium is a lustrous, silvery, ductile metal that has a closely packed hexagonal crystal structure. The tough, dense oxide film on its surface helps to protect the metal from corrosion. The metal is also not affected by alkalis and acids except for hydrofluoric acid. However it will react with oxygen, nitrogen, carbon, boron, sulfur and silicon.

Hafnium is chemically similar to zirconium. Most of the hafnium is procured from the titanium ores - ilmenite and rutile – deposits, which yield most of the zirconium.

Chemical Properties

The chemical properties of hafnium (rod) are provided in the table below.

Chemical Data
CAS number 7440-58-6
Ionic radius 0.780 Å
Electronegativity 1.3
X-ray absorption edge 0.18981 Å

Physical Properties

The following table discusses the physical properties of hafnium.

Properties Metric Imperial
Density 13.31 g/cm3 0.4809 lb/in3
Melting point 2200 °C 3992°F
Boiling point 5200 °C 9392°F

Mechanical Properties

The mechanical properties of hafnium are tabulated below.

Properties Metric Imperial
Tensile strength 485 MPa 70300 psi
Yield strength 125 MPa 18100 psi
Poisson's ratio 0.265 0.265
Shear modulus 54 - 58 Gpa 7.83204- 8.41219 psi
Elongation at break 25% 25%

Thermal Properties

The thermal properties of hafnium are tabulated below.

Properties Metric Imperial
Thermal expansion co-efficient (@20-100°C/68-212°F) 5.90 µm/m°C 3.28 µin/in°F
Thermal conductivity 22 W/mK 153 BTU in/hr.ft².°F

Applications

The following are the application areas of hafnium:

  • In filaments and electrodes
  • In superalloys
  • As the electrode in plasma cutting
  • In gas-filled and incandescent lamps
  • In vacuum tubes as a getter
  • In control rods in nuclear power plants

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