Hafnium is a lustrous, silvery gray, tetravalent transition metal, hafnium chemically resembles zirconium and is found in many zirconium minerals. Hafnium’s large neutron capture cross-section makes it a good material for neutron absorption in control rods in nuclear power plants, but at the same time requires that it be removed from the neutron-transparent corrosion-resistant zirconium alloys used in nuclear reactors.
|Element category||Transition Metal|
|Phase at STP||Solid|
|Ultimate Tensile Strength||480 MPa|
|Yield Strength||125 MPa|
|Young’s Modulus of Elasticity||78 GPa|
|Brinell Hardness||1700 MPa|
|Vickers Hardness||1700 MPa|
|Melting Point||2227 °C|
|Boiling Point||4600 °C|
|Thermal Conductivity||23 W/mK|
|Thermal Expansion Coefficient||5.9 µm/mK|
|Specific Heat||0.14 J/g K|
|Heat of Fusion||24.06 kJ/mol|
|Heat of Vaporization||575 kJ/mol|
|Electrical resistivity [nanoOhm meter]||331|
|Magnetic Susceptibility||+75e-6 cm^3/mol|
Applications of Hafnium
Hafnium has good neutron-absorbing properties, and hence it is used in control rods in nuclear reactors, but at the same time requires that it be removed from the neutron-transparent corrosion-resistant zirconium alloys used in nuclear reactors. While hafnium nitride is the most refractory of all the metal nitrides, hafnium carbide is the most refractory of all the binary materials. With a melting point of about 3900 °C it is one of the most refractory binary compounds known. Hafnium has been successfully alloyed with several metals including iron, titanium and niobium.
Production and Price of Hafnium
Raw materials prices change daily. They are primarily driven by supply, demand and energy prices. In 2019, prices of pure Hafnium were at around 1200 $/kg.
The heavy mineral sands ore deposits of the titanium ores ilmenite and rutile yield most of the mined zirconium, and therefore also most of the hafnium. Zirconium is a good nuclear fuel-rod cladding metal, with the desirable properties of a very low neutron capture cross-section and good chemical stability at high temperatures. However, because of hafnium’s neutron-absorbing properties, hafnium impurities in zirconium would cause it to be far less useful for nuclear-reactor applications. Thus, a nearly complete separation of zirconium and hafnium is necessary for their use in nuclear power. The production of hafnium-free zirconium is the main source for hafnium.
Mechanical Properties of Hafnium
Strength of Hafnium
In mechanics of materials, the strength of a material is its ability to withstand an applied load without failure or plastic deformation. Strength of materials basically considers the relationship between the external loads applied to a material and the resulting deformation or change in material dimensions. In designing structures and machines, it is important to consider these factors, in order that the material selected will have adequate strength to resist applied loads or forces and retain its original shape. Strength of a material is its ability to withstand this applied load without failure or plastic deformation.
For tensile stress, the capacity of a material or structure to withstand loads tending to elongate is known as ultimate tensile strength (UTS). Yield strength or yield stress is the material property defined as the stress at which a material begins to deform plastically whereas yield point is the point where nonlinear (elastic + plastic) deformation begins.
See also: Strength of Materials
Ultimate Tensile Strength of Hafnium
Ultimate tensile strength of Hafnium is 480 MPa.
Yield Strength of Hafnium
Yield strength of Hafnium is 125 MPa.
Modulus of Elasticity of Hafnium
The Young’s modulus of elasticity of Hafnium is 125 MPa.
Hardness of Hafnium
In materials science, hardness is the ability to withstand surface indentation (localized plastic deformation) and scratching. Brinell hardness test is one of indentation hardness tests, that has been developed for hardness testing. In Brinell tests, a hard, spherical indenter is forced under a specific load into the surface of the metal to be tested.
Brinell hardness of Hafnium is approximately 1700 MPa.
The Vickers hardness test method was developed by Robert L. Smith and George E. Sandland at Vickers Ltd as an alternative to the Brinell method to measure the hardness of materials. The Vickers hardness test method can be also used as a microhardness test method, which is mostly used for small parts, thin sections, or case depth work.
Vickers hardness of Hafnium is approximately 1700 MPa.
Scratch hardness is the measure of how resistant a sample is to permanent plastic deformation due to friction from a sharp object. The most common scale for this qualitative test is Mohs scale, which is used in mineralogy. The Mohs scale of mineral hardness is based on the ability of one natural sample of mineral to scratch another mineral visibly.
Hafnium is has a hardness of approximately 5.5.
See also: Hardness of Materials
Hafnium – Crystal Structure
A possible crystal structure of Hafnium is hexagonal close-packed structure.
In metals, and in many other solids, the atoms are arranged in regular arrays called crystals. A crystal lattice is a repeating pattern of mathematical points that extends throughout space. The forces of chemical bonding causes this repetition. It is this repeated pattern which control properties like strength, ductility, density, conductivity (property of conducting or transmitting heat, electricity, etc.), and shape. There are 14 general types of such patterns known as Bravais lattices.
See also: Crystal Structure of Materials
Thermal Properties of Hafnium
Hafnium – Melting Point and Boiling Point
Melting point of Hafnium is 2227°C.
Boiling point of Hafnium is 4600°C.
Note that, these points are associated with the standard atmospheric pressure.
Hafnium – Thermal Conductivity
Thermal conductivity of Hafnium is 23 W/(m·K).
The heat transfer characteristics of a solid material are measured by a property called the thermal conductivity, k (or λ), measured in W/m.K. It is a measure of a substance’s ability to transfer heat through a material by conduction. Note that Fourier’s law applies for all matter, regardless of its state (solid, liquid, or gas), therefore, it is also defined for liquids and gases.
Coefficient of Thermal Expansion of Hafnium
Linear thermal expansion coefficient of Hafnium is 5.9 µm/(m·K)
Thermal expansion is generally the tendency of matter to change its dimensions in response to a change in temperature. It is usually expressed as a fractional change in length or volume per unit temperature change.
Hafnium – Specific Heat, Latent Heat of Fusion, Latent Heat of Vaporization
Specific heat of Hafnium is 0.14 J/g K.
Heat capacity is an extensive property of matter, meaning it is proportional to the size of the system. Heat capacity C has the unit of energy per degree or energy per kelvin. When expressing the same phenomenon as an intensive property, the heat capacity is divided by the amount of substance, mass, or volume, thus the quantity is independent of the size or extent of the sample.
Latent Heat of Fusion of Hafnium is 24.06 kJ/mol.
Latent Heat of Vaporization of Hafnium is 575 kJ/mol.
Latent heat is the amount of heat added to or removed from a substance to produce a change in phase. This energy breaks down the intermolecular attractive forces, and also must provide the energy necessary to expand the gas (the pΔV work). When latent heat is added, no temperature change occurs. The enthalpy of vaporization is a function of the pressure at which that transformation takes place.
Hafnium – Electrical Resistivity – Magnetic Susceptibility
Electrical property refers to the response of a material to an applied electric field. One of the principal characteristics of materials is their ability (or lack of ability) to conduct electrical current. Indeed, materials are classified by this property, that is, they are divided into conductors, semiconductors, and nonconductors.
See also: Electrical Properties
Magnetic property refers to the response of a material to an applied magnetic field. The macroscopic magnetic properties of a material are a consequence of interactions between an external magnetic field and the magnetic dipole moments of the constituent atoms. Different materials react to the application of magnetic field differently.
See also: Magnetic Properties
Electrical Resistivity of Hafnium
Electrical resistivity of Hafnium is 331 nΩ⋅m.
Electrical conductivity and its converse, electrical resistivity, is a fundamental property of a material that quantifies how Hafnium conducts the flow of electric current. Electrical conductivity or specific conductance is the reciprocal of electrical resistivity.
Magnetic Susceptibility of Hafnium
Magnetic susceptibility of Hafnium is +75e-6 cm^3/mol.
In electromagnetism, magnetic susceptibility is the measure of the magnetization of a substance. Magnetic susceptibility is a dimensionless proportionality factor that indicates the degree of magnetization of Hafnium in response to an applied magnetic field.
Application and prices of other elements