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Hafnium, Hf, 72
Transition metal
2506 K (2233 °C)
4876 K (4603 °C)
Hexagonal densest packing (α-Hf)
13.31 g/cm³ (at 20 °C)
5,5
33.1 µΩ-cm (at 20 °C)
Physical properties
Hafnium is a shiny silver, easily malleable heavy metal. It is very dense, chemically resistant and resistant to corrosion.
It absorbs neutrons particularly strongly and is therefore one of the most effective neutron scavengers of all. At the same time, hafnium has a very high melting point of 2233 °C and remains stable even in extreme heat. Like many other metals, hafnium forms a protective oxide layer on its surface, which protects it from further corrosion.
These properties - strong neutron absorption, heat resistance and corrosion stability - make hafnium a valuable material wherever extreme conditions prevail.
Characteristic properties
Hafnium and zirconium are chemically almost identical and always occur together in nature. Unlike its twin, hafnium cannot be extracted primarily, as it is found exclusively in zirconium ores, in a ratio of around 1:50 to its twin metal. However, it is not always extracted from these ores: as separation is technically complex and expensive, hafnium is only produced as a raw material when demand justifies it.
The reason for this difficulty is the chemical proximity of the two metals: they react to the same chemicals and behave almost identically when heated, so that conventional separation processes do not recognize them as different substances. Many technically complex and expensive steps are required to separate them - which is why pure hafnium is an expensive raw material despite its widespread use.
Meaning and applications
Discovered in Copenhagen in 1923 by Dirk Coster and Georg von Hevesy, the metal plays an important role in nuclear technology, microelectronics and high-performance alloys for use in turbines and other high-temperature applications. Due to its strong neutron absorption, hafnium is used in the control rods of nuclear reactors, where it safely regulates the chain reaction.
Even small amounts of hafnium significantly increase the heat resistance and strength of alloys, allowing them to be used at temperatures above 1,000 °C. Such high-performance alloys are indispensable for modern engines in the aerospace industry.
Hafnium has also become indispensable in the semiconductor industry: hafnium oxide (HfO₂) is used in transistors and enables computer chips to be made even smaller while consuming less power. Intel first used this material in series production in 2007.
According to analyses by the European Commission, hafnium is considered a critical raw material. Demand is likely to increase due to the global expansion of nuclear energy, the growing need for