Rhenium

Background
Rhenium, as a pure refractory metal, is extremely attractive for high temperature structural and energy system applications, such as space and missile propulsion systems. Used either as a pure structural material or as a liner in conjunction with graphite or carbon-carbon structural materials, rhenium can provide erosion resistance for components in high temperature rocket engines and hot gas valves. Rhenium has many advantages over other candidate liner materials. Rhenium has a melting point of 3180°C (5756°F), exceeding all other metals except tungsten. Unlike tungsten, however, rhenium has a ductile-to-brittle transition temperature well below room temperature. Additionally, thruster nozzles fabricated from rhenium have undergone over 100,000 thermal fatigue cycles from room temperature to over 2200°C (4000°F) without any evidence of failure . With regard to use as a coating on carbon materials, rhenium is the only refractory metal that does not form a carbide, yet it has a significant solubility for carbon which ensures an excellent bond strength between the two materials. Rhenium has repeatedly outperformed all other coating candidates on solid rocket hot section components in tests.

Rhenium also possesses a wear resistance second only to osmium among the metallic elements, and the highest strain hardening coefficient of any metal.

Because of its very high melting point, rhenium is used to make high temperature alloys (an alloy is a mixture of metals) that are used in jet engine parts. It is also used to make strong alloys of nickel-based metals. Rhenium alloys are used to make a variety of equipment and equipment parts, such as temperature controls, heating elements, mass spectrographs, electrical contacts, electromagnets, and semiconductors. An alloy of rhenium and molybdenum is a superconductor of electricity at very low temperatures. These superalloys account for the majority of the rhenium use each year.

Rhenium is also used in the petroleum industry to make lead-free gasoline. In this application, rhenium compounds act as catalysts. (A catalyst is a chemical compound that takes part in a chemical reaction, and can often make the reaction proceed more quickly, but the chemical is not consumed in the chemical reaction.)

High-temperature strength, low friction, ductility and other rather unique properties make it the material of choice for many critical applications.

Sources
Rhenium is a very rare element that is produced principally as a by-product of the processing of porphry copper-molybdenum ores. Because it is scarce, very little rhenium is actually processed and isolated each year as compared to the millions of tons of copper and millions of pounds of molybdenum that are extracted from these same porphry copper deposits. Rhenium is obtained almost exclusively as a by-product of the processing of a special type of copper deposit known as a porphyry copper deposit. Specifically, it is obtained from the processing of the mineral molybdenite (a molybdenum ore) that is found in porphyry copper deposits. A porphyry copper deposit is a valuable copper-rich deposit in which copper minerals occur throughout the rock. The copper in these deposits occurs as primary chalcopyrite (CuFeS2) or the important secondary copper mineral chalcocite (Cu2S).

The identified rhenium resources in the United States are estimated to total 5 million kilograms. These resources are found in the southwestern United States. The identified rhenium resources in the rest of the world are estimated to total 6 million kilograms. Countries producing rhenium include Armenia, Canada, Chile, Kazakhstan, Mexico, Peru, Russia, and Uzbekistan. Even though the United States has significant rhenium resources, the majority of the rhenium consumed in the U.S. is imported. Chile and Kazakhstan provide the majority of the imported rhenium. The rest is imported from Mexico and other nations.