It belongs to the transition element of Group VIII of the periodic table, with the element symbol Ir, atomic number 77, atomic weight 192.2, face-centered cubic lattice, and is a rare precious metal material.
A brief history: In 1803, S. Tennant of England discovered iridium in the black residue after separating platinum; in 1813, the first melting experiment of iridium was conducted; in 1860, the Russian Mint used About 8kg of raw iridium-containing materials and other residues are used as raw materials for smelting to obtain an iridium ingot weighing 1.805kg. In 1881, J. Holland applied for a U.S. patent titled "Process for Melting and Casting Iridium." Since then, metallurgists in various countries have done a lot of work to solve the processing problems of iridium.
Performance: The main properties of iridium are: ⑴ Density 22.56g/cm^3; ⑵ Melting point 2454℃, the use temperature of iridium products can reach 210 0 ~ 2200¨C; ⑶ High elastic modulus (538.3 GPa), low Poisson coefficient (0.26), and poor low-temperature plasticity; (4) It is the most corrosion-resistant metal. Dense iridium is insoluble in all inorganic acids and is not corroded by other metal melts, such as molten lead, zinc, Nickel, iron, gold, etc.; can withstand the erosion of many molten reagents and high-temperature silicates; ⑸ Like other platinum group metal alloys, iridium alloys can firmly absorb organic matter and can be used as catalyst materials; ⑹ Iridium is 600°C in air or oxygen The above generates IrO2 and decomposes at 1100°C; the volatilization amount of iridium in the air at 1227°C is 100 times that of platinum. Iridium can be smelted using high-frequency or medium-frequency furnaces, electric arc furnaces, electron beams, etc. Iridium has good plasticity above 1600°C and is usually hot processed.
Uses: The high melting point and high stability of iridium make it important in many special occasions. However, the brittleness and high temperature loss of iridium limit its application to a certain extent. The earliest application of iridium was as a pen tip material, and later it was used in injection needles, balance blades, compass holders, electrical contacts, etc. Iridium crucible can be used to grow refractory oxide crystals. The crucible can work at 2100 to 2200°C for thousands of hours and is an important precious metal vessel material. Iridium's high-temperature oxidation resistance and thermoelectric properties make the iridium/iridium-rhodium thermocouple the only precious metal temperature measurement material that can measure temperatures up to 2100°C in the atmosphere; it can be used as a container material for radioactive heat sources; anodized iridium film is a useful Promising electrochromic materials. Ir192 is a gamma ray source that can be used for non-destructive testing and radiochemical treatment. At the same time, iridium is a very important alloying element. Some iridium alloys are used in certain key sectors; iridium compounds also have their own unique uses.