Iridium: belongs to the periodic table Ⅷ transition element, atomic number 77, atomic number 192. 2, face-centered cubic lattice, is a rare precious metal material. Two new elements, osmium and iridium, were found in the black powder left at the bottom of the vessel when the crude platinum was dissolved in royal water. Iridium content in the earth's crust is one part in ten million and is often dispersed in alluvial and sandy deposits with platinum series elements. Two isotopes exist in nature: iridium 191 and iridium 193.
The main properties of iridium are:
(1) density 42 g/cm ^ 3;melting point 2454 ℃, iridium products use temperature can reach 210℃~ 2200 ℃;
(2) high elastic modulus (538.3GPa), low poisson coefficient (0.26), poor plasticity at low temperature;
(3) of the most corrosion resistant metals, dense iridium is insoluble in all inorganic acids, also is not corroded by other metal melts, such as molten lead, zinc, nickel, iron, gold and so on; Resistance to many melting reagents and high temperature silicate corrosion;
(4) like other pge metal alloys, iridium alloy can firmly absorb organic matter and can be used as catalyst material;
(5) iridium above 600 ℃ in air or oxygen generated IrO2, and dissolved in 1100 ℃; At 1227 ℃ in air volatilize quantity is 100 times of platinum iridium. Iridium can be smelted by high frequency or intermediate frequency furnace, arc furnace, electron beam furnace, etc. Iridium in above 1600 ℃ has good plasticity, usually for hot working.
Uses of iridium:
The high melting point and high stability of iridium make it useful in many special applications.
The first use of iridium was as a pen point material, and later came the use of injector needles, balance blades, compass holders, electric contacts and the like. Iridium crucible refractory oxide crystal growth which can be used, the crucible can thousands of hours in 2100 ~ 2200 ℃, material is an important precious metal vessels.
High temperature oxidation resistance and thermoelectric properties of iridium make iridium/it rhodium thermocouple can be measured in the atmosphere only precious metal temperature of 2100 ℃ high temperature materials; Container materials that can be used as radioactive heat sources; The anodic iridium oxide membrane is a promising electrochromogenic material. Ir192 is a gamma ray source and can be used for nondestructive inspection and radiochemotherapy.
At the same time, iridium is an important alloying element. Some iridium alloys are used in some key sectors. Iridium compounds also have specific USES.