rhenium
Rhenium is a chemical element, the symbol is Re, the atomic order is 75. Rhenium is a silver-white heavy metal that belongs to the 6th cycle transition metal in the periodic table. It is one of the most rare elements of the earth's crust, with an average content of one billionth of a value, and one of the highest melting and boiling points. Rhenium is a by-product of molybdenum and copper refining processes. Its chemical properties and manganese and 鍀 similar, in the compound of the oxidation state of up to -3, up to +7. Scientists discovered rhenium elements in 1925, so it became the final stable element found. Its name (Rhenium) is taken from the Rhine in Europe. The nickel rhenium superalloy can be used to make the combustion engine, turbine blades and exhaust nozzles of the jet engine. These alloys contain up to 6% rhenium, which is the largest practical application of rhenium, followed by the catalyst in the chemical industry. Rhenium is more difficult to obtain than diamonds, so the price is high, August 2011 average of $ 4,575 per kilogram ($ 1,2030 per troy ounce). Because rhenium can be used in high-performance jet engine and rocket engine, so the military strategy is very important. ...