1. Superconducting application
It has been found for a long time that when the temperature drops to near absolute zero, the chemical properties of some substances will suddenly change into a "superconductor" with almost no resistance. The temperature at which matter begins to have this strange "superconducting" property is called the critical temperature. Needless to say, the critical temperatures of various substances are different.
There are many elements with superconductivity. Niobium is the highest critical temperature. The alloy made of niobium, whose critical temperature is as high as 18.5-21 ℃, is the most important superconducting material at present.
2. Superalloy
Most of the world's niobium is used to produce nickel, chromium and iron-based superalloys in the form of pure metal or high-purity ferroniobium and niobium nickel alloys. These alloys can be used in jet engines, gas turbine engines, rocket components, turbochargers and heat-resistant combustion equipment. In the grain structure of the superalloy, niobium will form the phase of γ ''. These alloys generally contain up to 6.5% niobium.
3. Niobium based alloy
C-103 alloy is a niobium alloy developed by Huachang company and Boeing company in the early 1960s. Due to the cold war and space race, many American companies, such as DuPont, United carbide and general electric, are developing niobium based alloys at the same time. Niobium and oxygen are easy to react, so the production process needs to be carried out in vacuum or inert gas environment, which greatly increases the cost and difficulty.
4. Medical application
Niobium also plays an important role in surgery and medicine. It can not only be used to make medical devices, but also is a good "biological adaptive material".
For example, niobium sheet can make up for the damage of skull, niobium wire can be used to sew nerves and tendons, niobium strip can replace broken bones and joints, niobium yarn or niobium mesh made of niobium wire can be used to compensate muscle tissue
5. Steel application
Among all kinds of microalloying elements in steel, waste niobium is the most effective microalloying element. The effect of niobium is so great that the iron atom is rich in niobium atoms, which can improve the properties of steel. In fact, adding 0.001% - 0.1% niobium into the steel is enough to change the mechanical properties of the steel.
The addition of niobium as a microalloying element into steel does not change the structure of iron, but it combines with carbon nitrogen sulfur in steel to change the microstructure of steel. The strengthening effect of niobium on steel is mainly fine grain strengthening and dispersion strengthening. Niobium can form stable carbides and carbonitrides with carbon and nitrogen in steel. It can also disperse carbides and form steel with fine crystallization.
Niobium can also be dispersed by inducing precipitation and controlling cooling rate. Adjust the toughness level of steel in a wide range. Therefore, the addition of niobium can not only improve the strength of the steel, but also improve the toughness, high temperature oxidation resistance and corrosion resistance of the steel.
6. Electric porcelain
Lithium niobate is a kind of ferroelectric material, which is widely used in the manufacture of mobile phone, optical modulator and surface acoustic equipment. Its crystal structure belongs to the ABO3 type, which is the same as lithium tantalate and barium titanate. Niobium can replace tantalum in tantalum capacitor and reduce cost, but tantalum capacitor is still superior.
7. Coins
On coins, niobium is sometimes used with gold and silver as precious metals in commemorative coins. A series of silver niobium euro coins were produced, the color of which was produced by the surface diffraction of oxide formed in the anodizing process.
8. Others
Niobium (or 1% zirconium) is the sealing material for arc tube of high pressure sodium lamp, because the thermal expansion coefficient of niobium is very similar to that of sintered alumina arc lamp ceramic material. This kind of ceramic used in sodium lamp can resist chemical erosion and will not react with the high temperature sodium liquid and gas in the lamp. Niobium is also used in arc welding strips to weld certain stabilized stainless steels. Niobium is used as anode material in the cathodic protection system of some large water tanks, and the anode is usually plated with a layer of platinum.