Porous Tungsten Ceramics Electrolysis

Tungsten is a refractory metal with the highest melting point and lowest vapor pressure in all metals. It has been widely used in aerospace, power electronics and metallurgical industry. Recently, tungsten-based porous ceramics have attracted more and more attention from researchers at home and abroad.

At present, the main methods to prepare porous tungsten ceramics are sintering, reactive sintering and dry sintering with organic matrix, but there are still some shortcomings in these methods. The traditional sintering method requires a high heating temperature, resulting in a very low porosity and uneven pore distribution; the reaction sintering method has a low heating temperature and uniform hardness distribution, but the porosity of the sample is very low; the organic matrix immersion drying sintering method has a simple process and operation equipment, but the heating temperature is high and the production efficiency is low.

Therefore, the preparation of porous tungsten urgently needs a new process which is easier to realize and can obtain better pore distribution. Electrolysis is a good method. Electrolysis is a common method to prepare metal materials by electrochemical anodic dissolution of metals in molten salts or aqueous electrolytes. Researchers believe that this technology can also be applied to the preparation of porous tungsten and other porous metals.

The tungsten block was polished to a smooth surface with 1000# sandpaper. It was washed with ultrasonic ethanol at a frequency of 28 KHz for 5-10 min with anhydrous ethanol, washed with distilled water, dried naturally, and then electrolyzed. The conditions for electrolysis were as follows: a temperature of 80 °C, a current density of 350 mA/cm² , and a time of 60 min. The electrolyte was a NaOH solution having a mass fraction of 10% by adding 0.5% sodium hexametaphosphate. The weight loss of the obtained tungsten is 25%, and the obtained specific surface area is increased by 16% compared with the case where no additive is added. It can be found through testing that adding an additive to the electrolyte effectively controls the increase of the area of the tungsten to form a porous tungsten structure. Finally, the weight loss of the tungsten block is 15%-30%, and the specific surface area is increased by 10%-40% compared with the additive.

Compared with the traditional process, the process does not need to be heated at high temperature. The process is simpler, the equipment is simple, the operation is convenient, and various process factors are easy to control and adjust.

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