Rhenium

Rhenium

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The Past

Why "rhenium"?

Ida and Walter Noddack and Otto Berg from Germany discovered rhenium. They named this element after river Rhine where Ida spent her youth, when she lived on the territory of today's Wesel. Back then, they also claimed to have discovered the second element with atomic number 43, which they called masurium (Polish Mazury was then part of Eastern Prussia from where Walter Noddack's family came). The name of the latter did not become customary as its discovery was not confirmed (today, 43rd element is known as technetium, in Polish - technet).

It is suspected that the Noddacks could have been German nationalists who wanted to commemorate the success of the German army in Mazury during I World War by naming the element in this particular way (for instance, famous from its propaganda the Tannenberg battle - today's Stębark - where the German Empire crushed twice as big army of the Russian Empire). However, in the upcoming years they did not join the Nazis, but they were not contesters either, and Walter, in 1930s, was offered a remunerative position at the university.

Did sexism stop atomic extermination?

Despite the huge success of rhenium discovery (element number 75 was the last element to be discovered in the form of a stable isotope on the Earth), Ida and Walter Noddack did not have a high position in the world of science. Ida received three Noble prize nominations, but without success. Unfortunately, having questioned the discovery of element 43 and their unclear connections with the regime, and the fact that Ida was a woman (except for Maria Skłodowska-Curie there were not many women scientists) - her important work was ignored.

When the famous scientists, Enrico Fermi, having shot neutrons at uranium, claimed that he created a bigger element, Ida Noddack reacted immediately. Why? Fermi thought that he managed to obtain the element with the atomic number of 93 (later neptunium), which he called eka-rhenium, so according to Mendelejev's terminology - "element under rhenium" and he placed it exactly there in the table. Ida Noddack questioned this and put forward a hypothesis that the Italian physicist had split the atom rather than enlarged it. The scientific environment considered this as absurd (the name "atom" means in Greek something that cannot be split). Only four years later, Otto Hahn, suggested, and then confirmed with experiments, the possibility to split an atom for which he won a Noble Prize in 1944. What would have happened if the scientists had followed the ideas of rhenium discoverer? For sure we know that the element itself named after the longest river in Germany did not make her famous since engineers of those times had troubles to obtain and apply it. Nevertheless, the Noddacks and Otto Berg will surely remain in the scientific annals.

How was this elusive element found?

The existence of rhenium was predicted a long time ago. Dimitrij Mendelejev himself on his table marked an empty space as dvi-mangan, which means an element two places below manganese. Masataka Ogawa, from Japan, was the first to have found rhenium, but mistakenly recognised it as element 43 (later technetium). Many years later, it turned out how close he was from the true discovery. He called it "nipponium", i.e. the Country of the Rising Sun in the language of Samurais - Japan. The Noddacks and Otto Berg, mentioned before, had at their disposal a more advanced technology of x-ray spectroscopy, which was available in Siemens laboratory, where Berg worked. How did they succeed?

Previous scientists were looking for element 75 in wrong places. They suspected it to have similar properties as manganese, and thus they were examining manganese minerals. But, the Noddacks rightfully noticed that the missing elements 43 and 75 will be rather more similar to their side neighbours in the periodic table of elements. In this way trace amounts of rhenium were found in the minerals like molybdenite. Having for years worked on the production methods, in 1928 they managed to obtain 1 gramme of rhenium from 660 kilograms of this mineral. In Poland, rhenium was found among copper deposits extracted by KGHM.

The present

What are rhenium's properties?

Rhenium is much appreciated for its high melting point (3186 °C 3rd highest temperature among elements after carbon and tungsten) and high boiling point (5596 °C the highest from all the elements). It is also one of the thickest metals. In temperatures close to absolute zero it becomes superconductive (10 Kelvin degrees (263,15 Celsius) is enough for an alloy of rhenium and molybdenum). It is soluble only in oxidative acids.

Owing to that property, it is used as an ingredient of superalloys in the aviation and rocket industry. From the mixture based on nickel, with from three to six percent of rhenium, monocrystalline (without joints) hollow blades for jet engines that need to be resistant to extreme temperatures and rotate very quickly are produced. Rhenium is also present where extremely high temperatures are present, i.e. electrical connections or special lamps. It is also applied in the production of X-ray devices. Rhenium is additionally a very efficient catalyst applied e.g. in the production of high octane unleaded fuel.

How is rhenium obtained?

Rhenium is one of the rarest elements in the Earth's crust. It is rarer than gold. Calculations give the number of one part of a billion which is like a drop of water per two average size tankers. It is also very much scattered. It does not have its own minerals in the ground (except for an extremely rare mineral found in volcanoes). There are no rhenium nuggets. Hence its high prices that in the period of high industry demand amounted to couple of thousand of dollars per kilogram. It is mainly extracted together with molybdenite (molybdenum disulfide) and copper. In Poland, rhenium is produced by KGHM Polska Miedź S.A.

Where in Poland is rhenium produced?

To the west of Wrocław, in Legnica, there is an only factory in Europe that produces metallic rhenium from its own resources. We rank third in the world in rhenium production. Daughter company of KGHM Polska Miedź S.A. - KGHM Ecoren - runs the production. Eminent Polish engineers have invented a method of rhenium recovery from copper production tailings, and, mind you, we are one of the largest copper powers. Except for Legnica, rhenium in the form of ammonium perrhenate is produced in "Głogów" Copper Smelter. Polish rhenium was used by e.g British chemical tycoon Johnson Matthey, established in 1812, which produces catalysts, for instance.

A prestige contract worth one hundred million dollars KGHM Ecoren have signed also with Rolls-Royce, whose 13 000 civil plane engines are in use at the moment. Polish rhenium could have also been applied in the production of such wonders of technology as the key elements of super modern engine of fifth generation combat aircraft Lockheed Martin F-35B Lightning II in STOVL variant, i.e. "short take-off and vertical-landing".

The Future

What is rhenium's future?

It seems that the production of modern aircraft engines will continue to develop. Also, petroleum and chemical industries will still need considerable amounts of rhenium. Hence, rhenium is still being explored. Many companies, like KGHM Ecoren, focus not only on the production, but also on the recovery of such a rare element from scrap. There is also a possibility to obtain it from magma, but it is still a thing of the future. The Russians have noticed that in the volcano on Iturup island (Etorofu) rhenium can be found and it leaves the inside of the Earth together with the gases. This particular location may become a source of conflict since the volcano partially lies on Kuril Islands to which the Japanese claim the property as they lost these islands after II World War.

In the future, rhenium, in large amounts, may be used to produce spaceship parts. Who knows, perhaps Polish rhenium produced by KGHM might be one of the building elements of a rocket that will transport our grandchildren to their first space colonies...