1. Aerospace
Precious metals mainly refer to 8 metal elements including gold, silver and platinum group metals (ruthenium, rhodium, palladium, osmium, iridium and platinum). Most of these metals have a beautiful color, strong chemical stability, and generally do not react with other chemicals. Platinum group metals, also known as platinum group elements. In the periodic table it has the 5th and 6th period. The family element is widely used in gemology, among which palladium jewelry - white precious metal new favorite, international fashion fashion jewelry platinum, palladium, the two metallurgical properties are quite similar, because of its same rare, similar use, so often in a variety of applications do substitutes for each other. Platinum group metals are also widely used in industry, electronic information, aerospace, military industry, environmental protection and other fields due to their superior physical and chemical properties. They have a small amount in these industries, but play a key role, so they are known as "industrial vitamins".
Platinum group metals not only have similar physical and chemical properties, but also have their own characteristics. Platinum group metal except osmium is blue gray metal, other are silver white metal. Most platinum group metals absorb gases, especially hydrogen. Palladium has the strongest hydrogen absorption capacity. At room temperature, one volume of palladium can absorb 900 ~ 2800 volumes of hydrogen. Heated to 100℃ in vacuum, the dissolved hydrogen is released completely. Palladium has both hydrogen-absorbing and hydrogen-permeating properties: a given volume of palladium at room temperature can absorb hydrogen up to 900 times or even 2,800 times larger than itself (see hydrogen storage materials). Platinum has a strong ability to absorb oxygen. One volume of platinum can absorb 70 volumes of oxygen. When the particle size is very fine, such as platinum black, palladium black or colloidal state, the adsorption capacity is stronger, so they have good catalytic properties. Pure platinum and palladium have good ductility, without intermediate annealing cold plastic deformation can reach more than 90%, can be processed into micron level filament and foil. Rhodium and iridium have good high temperature strength, but poor cold plastic machining performance. Osmium and ruthenium hardness is high, but the mechanical processing performance is poor, with powder metallurgy method of ruthenium metal in 1150 ~ 1500℃ to carry out a small amount of plastic processing, and osmium even at high temperature can hardly carry out plastic processing.
Platinum group metals and alloys have many important industrial USES. In the past, distilleries were mainly used to produce dilute sulfuric acid by concentrating lead chamber. Standard meter sticks and weights were also made by using platinum-iridium alloy. In the mid-19th century, platinum-iridium and gold COINS were made in Russia. In the early years, "platinum black printing" was adopted in photography, and platinum salt was widely used to make beautiful and lasting photos.
