Tantalum and niobium are elements with similar properties, due to their high melting point (tantalum's melting point is 2996℃, niobium's melting point is 2468°C), low steam pressure, good cold working performance, strong resistance to liquid metal corrosion and strong acid corrosion except hydrofluoric acid, high chemical stability, and good dielectric properties of their oxide films. Therefore, tantalum and niobium are processed into rods, plates, sheets, tubes, wires, foams and other materials, which are widely used in the manufacture of electrolytic capacitor anodes, heating parts in high temperature vacuum furnaces, material plates and thermal insulation parts, anti-corrosion materials for chemical equipment and sputtering target materials for the barrier layer between copper wires and silicon in integrated circuits. The largest use is to manufacture electrolytic capacitors, tantalum, niobium powder and tantalum wire, niobium wire used as capacitor anode, tantalum, niobium sheet used for deep processing into the shell of electrical containers.
The processing methods of tantalum and niobium are smelting ingot rolling, drawing processing and powder metallurgy rolling drawing processing. In the former, tantalum and/or niobium powders are pressed into strips for sintering, followed by electron beam melting and/or arc melting, followed by processing; In the latter, high purity tantalum and/or niobium powders are pressed into shape, sintered and processed. The latter method has short process route, high yield, more convenient to get fine grain and uniform texture processing material, has better processing performance, and the product life is longer.
According to the different uses of tantalum and niobium powder, there are different requirements for its chemical purity and physical characteristics. As raw materials for powder metallurgy, such as tantalum and/or niobium powders, must have high purity and low expected interstitial element content so that the resulting billets have good ductility. For example, tantalum powders have expected oxygen content below 1500ppm and nitrogen content below 200 m. Niobium powder is expected to have similar levels of impurities.
Tantalum and niobium powders are usually produced by sodium metal, potassium tantalate or potassium fluomobate. The powders obtained are porous condensed particles with large specific surface area and small loose density. The loose density of sodium reduced tantalum powder is usually less than 3.5g /cm, 2(the density of TC tantalum is 16.64g /cm3). The loose density of sodium reduced niobium powder is usually less than 1.8g /cm3(2(the density of TC niobium is 8.66g /cm3); The corresponding oxygen content is also higher.
