Hobbies And Interests
Filaments
Purified rhenium does not melt at temperatures below 3,180 degrees Celsius. This makes rhenium wire a material of choice for thin filaments that must repeatedly withstand intense bursts of heat, such as coils in reusable photo flashbulbs and in mass spectrometers.
Space Craft Thrusters
Only the elements platinum, iridium and osmium exceed rhenium in density. Because of its high density, compressed rhenium powder forms superhard metallic shapes that do not deform easily when struck and do not expand or contract to a significant degree when heated or cooled. Looking for a material that could withstand physical punishment and wide ranges of temperatures for thrusters for its spacecraft, NASA began employing compressed rhenium thrusters in the 1960s and continues to do so.
Thermocouples
Thermocouples serve as emergency "off" switches in machines and electrical systems. When the temperature in the machine or system exceed the melting point of the material from which the thermocouple is made, the thermocouple destructs and the device shuts down. A commonly used thermocouple in high-temperature devices consists of a rhenium-tungsten ally that melts at 2,200 degrees Celsius.
Electrical Contacts
Each of the properties that make rhenium-based metals preferred choices for filaments, rocket thrusters and thermocouples also make the materials good options for electrical contacts. Rhenium metals do not oxidize (i.e., burn) when hit with electric arcs, nor do they become damaged when they get wet. Also, only diamond can scratch rhenium. When cooled to just above absolute zero, rhenium-molybdenum alloy becomes superconductive.
Chemical Catalysts
Refiners use a rhenium-platinum mixture to remove lead from gasoline. Rhenium also bonds easily with hydrogen, making it an attractive additive for chemical compounds used to absob hydrogen. For example rhenium sulfite denatures nitrobenzene, making the nitrobenzene less reactive and toxic.
Coatings
Mixed with oxygen and sometimes fluoride and powdered, rhenium powders get used for optical coatings and corrosion-resistant coatings for metal. Rhenium is also available in liquid solutions for coating as rhenium nitrate, rhenium acetate and rhenium chloride. Materials coated with rhenium compounds often see use as refractories in metal smelters. A refactory, according to the Refractories Institute, is the lining of furnace or reactor that protects the device and its users from heat.