Tantalum and niobium are rare elements and their properties are very similar. Since the oxide films of tantalum and niobium have very high dielectric constants, they are widely used in the manufacture of tantalum and/or niobium electrolytic capacitors. In addition, tantalum and/or niobium are also used in aerospace, defense, high-temperature vacuum furnaces heating components, boats and insulation materials because of their high melting point and low vapor pressure. In addition, tantalum and/or niobium have excellent corrosion resistance to liquid metals and strong acids other than hydrofluoric acid, and have good thermal conductivity and chemical stability, and are also used in chemical and metallurgical fields of anti-corrosion materials. In addition, because of their good biocompatibility, tantalum and/or niobium are often used in the medical field as surgical sutures, custom prosthetics, interbody fusion devices, artificial joints, bone injury repair materials, etc. Tantalum has a strong resistance to electronic stress migration, so it can also be used to make a barrier layer between copper wire and silicon in integrated circuits.
When tantalum and/or niobium are used to make electrolytic capacitors, a porous anode block is usually prepared using tantalum and/or niobium raw materials in powder form, and a tantalum and/or niobium wire is also inserted as the lead when the anode block is made, and tantalum sheet or niobium sheet is often used to process the capacitor shell. In other applications, in most cases tantalum and/or niobium powder is first pressed into rods or strips, then sintered, or even further electron beam melting or arc melting in order to achieve densification and high purification; This is followed by rolling, drawing and other processing to form rods, plates, sheets, tubes, wires, foils and other tantalum and/or niobium products.
Compared with tantalum and/or niobium powder for powder metallurgy, tantalum and/or niobium powder for capacitors is characterized by: in addition to the requirements for loose density, oxygen, nitrogen, hydrogen and other impurity content, more importantly, it is required to have good electrical properties. Generally, the higher the specific volume of tantalum and/or niobium powder used in capacitors, the larger the specific surface area, the smaller the loose pack density, and the higher the content of impurities such as oxygen, nitrogen and hydrogen. For example, tantalum powder for capacitors with a capacity of 200,000μFV/g has a loose pack density of 1.5-1.9g/cm3, an oxygen content of 9,000-12,500ppm, a hydrogen content of 350-500ppm, and because the production process must be doped with nitrogen, the nitrogen content will usually reach 1,500-2,800 PPM.
