Rinsing method of potassium fluotantalate product obtained through sodium reduction

Abstract

The invention relates to a rinsing method and device of a potassium fluotantalate product obtained through sodium reduction. The rinsing method comprises the following steps: using sodium to reduce potassium fluotantalate and obtain coagulum, crushing the coagulum, diafiltrating, rinsing, stirring to rinse, pickling, and drying to obtain raw tantalum powder. The obtained tantalum powder has high purity and good porosity and can be used to prepare condensed tantalum powder which is particularly suitable for the manufacture of the electrolytic capacitor.

Description

technical field [0001] The invention relates to the field of hydrometallurgy, in particular to a method and a device for washing and recovering tantalum powder from a product of reducing sodium to potassium fluorotantalate. Background technique [0002] The biggest use of tantalum powder is to manufacture electrolytic capacitors. The development trend of tantalum capacitors requires [0003] Has high capacitance, low leakage current and low equivalent series resistance (low tgδ for anode). As the main raw material of tantalum electrolytic capacitor, tantalum powder requires high specific surface area, good porosity and low impurities, especially low O, K and Na. Oxygen in tantalum powder includes surface oxygen, dissolved oxygen and compound oxygen. Compound oxygen has the greatest impact on capacitor leakage current. For example, oxygen contained in metatantalate will cause high leakage current and low breakdown voltage of capacitors. [0004] The chemical method to prepa...

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Problems solved by technology

The defect of the first method is that the condensed particles containing tantalum powder are stirred at high speed in the stirring tank. Due to the high-speed movement of the condensed particles, they hit the container wall or the baffle and are strongly squeezed, so that the original tantalum powder The particles are squeezed to bond with each other, and the pores between the particles are very small or even have no pores. In this way, in the subsequent heat treatment, the pores between the primary particles of the tantalum powder are very small and even the particles that are in contact with each other are sintered together, resulting in loss of surface area, and the particles The internal pores are small, resulting in high tantalum anode loss (tgδ); and, due to the residual alkali metal potassium and sodium in the sodium-reduced potassium fluorotantalate product, a strong alkaline solution is formed during stirring, which increases the temperature of the solution, and the tantalum The powder is soaked in hot alkaline solution for a long time to generate alkaline tantalate or metatantalate, resulting in high O, K and Na levels in tantalum powder.

If it is simply washed by filtration and water, since the sodium-reduced tantalum powder is composed of many submicron-sized primary particles ranging from a hundred nanometers to hundreds of nanometers, it is a very irregular agglomerated particle of varying sizes from a few microns to hundreds of microns. The alkali metal impurities mixed in it, especially the metatantalate formed by the reaction of alkali metal and tantalum, are difficult to wash off, resulting in high K, Na and O contents in tantalum powder.

Moreover, the size of the particles is too large, which is not conducive to granulation to produce cohesive tantalum powder with good fluidity, so it seriously affects the physical and electrical properties of tantalum powder used as electrolytic capacitors

[0007] Among them, the fluidity of tantalum powder is the time it takes for 50 grams of tantalum powder to pass through a conical funnel with a small hole of 5 mm in diameter. trouble

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