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Hafnium is used for the production of high-temperature alloys due to its very high melting point of 2,233 °C. These so-called superalloys are characterized by exceptional thermal stability and corrosion resistance: They retain their mechanical properties even under extreme conditions.
In alloys with metals such as niobium, tantalum, molybdenum and tungsten, an addition of around 2 % hafnium already has a strength-enhancing effect. This results in particularly stable and heat-resistant materials. The main customer is the aviation industry: in the hot section of jet engines, hafnium is used in the superalloy MAR M 247, for example, which is used for turbine blades and guide vanes. Alloys containing hafnium are also used in the aerospace industry. Around 10 % of the niobium-based alloy in rocket engine nozzles consists of hafnium.
An important area of application for hafnium is nuclear energy, where it helps to control nuclear fission and increase reactor safety. The metal is used in particular in control rods in various types of reactors, including pressurized water reactors, which are among the most frequently operated reactors in the world. Control rods are used to regulate the chain reaction in the reactor core by absorbing excess neutrons. This allows the reactor output to be precisely controlled and enables a rapid shutdown in an emergency.
Hafnium is particularly suitable for use in control rods as it can capture neutrons very effectively. At the same time, the material is extremely heat and corrosion resistant. These properties are crucial, as control rods in the reactor core are exposed to extreme temperatures and intense radiation.
Compared to other absorber materials, hafnium also has a high level of operational stability, as it remains functional for a long time even under constant neutron irradiation. This saves maintenance costs and makes reactor operation more reliable.
In addition to control rods, hafnium is also used in other reactor components where targeted neutron absorption is required. These include shielding elements between different reactor zones and safety components that also contribute to reactor shutdown in an emergency.
Hafnium plays an important role in the semiconductor industry. Hafnium oxide, a compound of hafnium and oxygen, is mainly used here. This material is used in modern computer chips as a so-called high-k dielectric, which serves as insulation for the control connection (gate) in field-effect transistors. It helps to better control electrical currents within the tiny transistors and reduce unwanted leakage currents. This enables chips to be more powerful and energy-efficient at the same time. Hafnium oxide has been used in many modern microprocessors since the mid-2000s. One future field of application could be ferroelectric data storage devices, which are being researched by the Fraunhofer Institute for Photonic Microsystems, among others.