Supplier Data - Thorium (Th) (Goodfellow)

Background

Thorium was discovered in 1829 by J.J. Berzelius in Stockholm.

Occurrence and Extraction

Thorium (Th) is a dark grey, radioactive metal of which the principal source is the ore, monazite, a complex phosphate of thorium, uranium, cerium and lanthanides. Thorium is soft and ductile and is extracted by precipitation as the hydroxide, along with cerium and uranium; separation is achieved by further extraction with tributyl phosphate from an acid solution. Thorium is made by calcium reduction of the oxide or fluoride, and pure thorium can be obtained by decomposing ThI4 on a hot filament (the Van Arkel process).

Applications

Thorium is used as an alternative reactor fuel to uranium, Thorium being converted readily into uranium in the reactor. Thorium is extremely efficient as an energy source, the earthly reserves of Thorium containing more energy than all other fossil fuel sources combined.

Thorium contains more energy than the majority of fossil fuels sources. Image Credit: SutterStock/P.V.R.Murty

Thorium contains more energy than the majority of fossil fuels sources. Image Credit: SutterStock/P.V.R.Murty

Key Properties

The key properties of Thorium are tabulated below.

Table 1. Key properties

Atomic Properties
Atomic number 90
Atomic radius - Goldschmidt ( nm ) 0.180
Atomic weight ( amu ) 232.0381
Crystal structure Face centred cubic
Electronic structure Rn 6d2 7s2
Photo-electric work function ( eV ) 3.5
Thermal neutron absorption cross-section ( Barns ) 7.4
Valences shown 2, 3, 4
Ionisation Potential No. eV
1 6.95
2 11.5
3 20.0
4 28.8
Natural Isotope Distribution Mass No. %
232 100
Electrical Properties
Electrical resistivity @ 20 °C ( µOhm.cm ) 14.0
Temperature coefficient @ 0-100 °C ( K-1 ) 0.0040
Superconductivity critical temperature ( K ) 1.38
Thermal emf against Pt (cold 0 °C - hot 100 °C) ( mV ) -0.13
Mechanical Properties
Material condition Soft Hard Polycrystalline
Bulk modulus ( GPa ) 54
Hardness – Vickers 38 70
Izod toughness ( J.m-1 ) 41 6
Poisson’s ratio 0.26
Tensile modulus ( GPa ) 78.3
Tensile strength ( MPa ) 115 305
Yield strength ( MPa ) 48 295
Physical Properties
Boiling point ( °C ) 4790
Density @ 20 °C ( g.cm-3 ) 11.5
Melting point ( °C ) 1750
Thermal Properties
Coefficient of thermal expansion @ 0-100 °C ( x10-6 K-1 ) 11.2
Latent heat of evaporation ( J.g-1 ) 2202
Latent heat of fusion ( J.g-1 ) 82.8
Specific heat @ 25 °C ( J.K-1.kg-1 ) 113
Thermal conductivity @ 0-100 °C ( W.m-1.K-1 ) 54

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