Refractory Alloys Refractory metals include tungsten (W), molybdenum (Mo), tantalum (Ta) and niobium (Nb). They have a BCC structure so they display a ductile to brittle transition temperature. Hot forming these materials aids their fabrication into useable products. Their metallic bonds are weak resulting in relatively low yield strengths. They have exceptionally high melting temperature (>1925 C) and so have high-temperature service. Mo and Ta have extremely good corrosion resistance so are used to contain acidic solutions at high temperatures.

Refractory Alloys Refractory metals include tungsten (W), molybdenum (Mo), tantalum (Ta) and niobium (Nb). These materials are expensive so find specialty applications. Applications include filaments for light bulbs (tungsten), penetrators, rocket nozzles, nuclear power generators (niobium), electronic capacitors (tantalum and niobium) and chemical processing equipment. These metals have a high density. The US army has recently developed W to be a penetrator (high impact bullet) to replace Urania penetrators. Urania contaminates the combat zone and surrounding area so required being replaced.

Precious Metals These include gold, silver, palladium and rhodium. They are precious and expensive. These materials resist corrosion and make very good conductors of electricity. As a result alloys of these materials are often used as electrodes for devices and to measure temperature as the thermocouples.

Precious Metals Gold, silver, palladium and rhodium Because of their corrosion resistance, they are used as nano-sized particles as catalysts in automobile exhaust systems and in petroleum refining. In exhaust gases, they facilitate the oxidation of CO to CO 2 and NO x to N 2 and O 2. Recently, Au nanoparticles have been used to fight cancer by being injected into and taken up by the cancer, which is then irradiated by a laser. The laser light is converted to a surface plasmon (collection of -ve charges) on the Au particle surface, which decay to phonons (atomic lattice vibrations), which heat the cancer cells and kill them.

Rare Earth Metals The Secret Ingredients of Everything!

Rare Earth Metals The Secret Ingredients of Everything

The End (Any questions or comments?)