Tantalum particles are made of skeleton tantalum powder as the core and superfine tantalum powder as the surface layer by sintering. Through reasonable particle size ratio design, the tantalum particles made are porous structures with BET specific surface area above 1.0m2/g and loose density between 1.6-2.1g/cm3. The particle size distribution will be tested: D10 is 29.92μm, D50 is 78.88μm, D90 is 149.4μm, which can be used as high quality capacitor grade tantalum powder. In the granulation process, the skeleton tantalum powder is freeze-dried first, and the expansion force of the phase transition of water is used to make the skeleton tantalum powder evenly dispersed. Then, a water film is formed during the fall of the skeleton tantalum powder by spraying water vapor, and the surface water film is used to bond the ultra-fine tantalum powder, so that the adjacent skeleton tantalum powder is separated and the skeleton tantalum powder is avoided to stick to each other, causing the problem of uneven composition.
In the selection of sodium-reduced tantalum powder, the bulk density of sodium-reduced tantalum powder is required to be greater than 0.4g/cm3 or the BET specific surface area is 0.7-6.0m2/g. In this embodiment, the commercial sodium-reduced tantalum powder is selected for testing, and the bulk density is 0.45g/cm3 and the BET specific surface area is 1.82m2/g, which meets the design requirements.
The sodium reduced tantalum powder is added to the crushing equipment for two stages of crushing, to obtain skeleton tantalum powder and ultrafine tantalum powder, respectively. The modal particle size of skeleton tantalum powder is required to be 1-2μm, the median particle size is 1-4μm, and the modal particle size of ultrafine tantalum powder is required to be 0.5-0.8μm, the median particle size is 0.6-1μm. The particle size of the two tantalum powder is tested, and the requirements are met.
