Rhenium, metal properties, characteristics and features

Rhenium is a very dense transition metal, designated as element 75 in the periodic table. Translated into Latin, it means "rhenus," the name of the Rhine River in Germany. Rhenium's discovery is comparatively recent—1925. It was discovered by German chemists, and in 1928, pure rhenium was extracted from Norwegian molybdenite. This was achieved by processing 600 kg of this rock. Not all chemical elements have a stable isotope, but rhenium does, making it the last element discovered to have one. Elements discovered later do not have stable isotopes.

Rhenium metal

Copper and molybdenum sulfide concentrates are used to obtain the metal; they are the most important raw materials for obtaining primary rhenium. Their approximate content can be 0.005% by weight. The geochemical properties of this metal are very similar to those of tungsten and molybdenum. Rhenium mining is difficult and expensive. Only one profitable rhenium deposit is known in the world: Iturup Island in the Kuril Islands, where it is found in the form of the mineral rhenite, a structure similar to molybdenite. The mineral tarkianite, which contains rhenium, has also been discovered in Finland.

Properties of rhenium

Rhenium is a very hard metal, with a density of 21.02 g/cm³. Its powder is dark gray or black. A high density requires a very high melting point; rhenium has a melting point of 31,860°C, which is lower than tungsten. Its boiling point, 55,960°C, is paramagnetic. It has a hexagonal crystal lattice. These figures indicate that it is a refractory metal and is very similar to tungsten and molybdenum, as well as the platinum group metals. It is ductile at room temperature, but after processing, the metal's hardness increases significantly due to strain hardening, due to its high modulus of elasticity.

Rhenium's mechanical properties allow it to withstand repeated heating and cooling without losing its strength. Even at temperatures of 12,000°C, its strength exceeds that of tungsten. Another advantage of rhenium over molybdenum and tungsten is that its electrical resistivity is four times higher.

Rhenium's chemical properties make it stable in air at room temperature. At temperatures above 3000°C, oxidation occurs, and at 6000°C, it becomes more intense. Among the platinum group metals, it is more resistant to oxidation and does not react directly with nitrogen and hydrogen. It reacts with elements such as bromine, chlorine, and fluorine only upon heating. It reacts weakly with sulfuric acid, even after heating, but dissolves readily in nitric acid.

Among refractory metals, rhenium does not form carbides. Its excellent hardness, strength, and stability allow it to be used:

• in the creation of parts for rocket technology and supersonic aviation;
• Combustion chambers, turbine blades, and exhaust nozzles for jet engines are made from nickel alloy;
• gas turbine engines containing heat-resistant nickel-rhenium metals;
• self-cleaning electrical contacts;
• in oil refining production.

Thus, it is clear that the properties of rhenium allow this valuable metal and its alloys to be used in a wide variety of industries, and it is finding new forms of application.