The traditional production methods of
bismuth powder include water mist method, gas atomization method and ball milling method; when the water mist method is atomized and dried in water, bismuth is easily oxidized due to the large surface area of bismuth powder; Under normal circumstances, the contact between bismuth and oxygen is also easy to cause a large amount of oxidation; both methods cause many impurities, irregular shape of
bismuth powder, and uneven particle distribution. The ball milling method is: artificially hammer bismuth ingots with stainless steel to bismuth grains of ≤10mm, or quench bismuth with water. Then the bismuth particles enter a vacuum environment, and the ball mill lined with ceramic rubber is pulverized. Although this method is ball milled in a vacuum, with less oxidation and low impurities, it is labor-intensive, time-consuming, low in yield, high in cost, and the particles are as coarse as 120 mesh. affect product quality. Invention patent CN201010147094.7 provides a production method of ultrafine bismuth powder, which is produced by wet chemical process, with large production capacity, short contact time between the whole production process and oxygen, low oxidation rate, less impurities, and the oxygen content of bismuth powder is 0< 0.6, uniform particle distribution; particle size -300 mesh.
1) Prepare bismuth chloride solution: get the bismuth chloride stock solution with a density of 1.35-1.4g/cm3, add acidified pure aqueous solution containing 4%-6% hydrochloric acid; the volume ratio of acidified pure aqueous solution and bismuth chloride stock solution is 1:1 -2;
2) Synthesis: add zinc ingots whose surface has been cleaned to the prepared bismuth chloride solution; start the displacement reaction; observe the end point of the reaction, when reaching the end point of the reaction, take out the undissolved zinc ingots and precipitate for 2-4 hours; The observation and judging basis of the described reaction end point is: there is bubble to emerge in the solution that participates in reaction;
3) Separation of bismuth powder: extract the supernatant of the precipitate in step 2) and reclaim zinc by conventional methods; the remaining precipitated
bismuth powder is stirred and washed 5-8 times with an acidified pure aqueous solution containing 4%-6% hydrochloric acid, and then washed with pure Rinse the bismuth powder with water to neutrality; after drying the bismuth powder quickly with a centrifuge, immediately soak the bismuth powder with absolute ethanol, and then dry it;
4) Drying: Send the bismuth powder treated in step 3) to a vacuum dryer at a temperature of 60±1°C for drying to obtain a finished bismuth powder of -300 mesh.
The advantage of the bismuth powder produced according to the above process is that the obtained product has high purity and fine particle size; therefore, the oxidation rate is low.
