Preparation method and introduction of bismuth powder

Preparation method and introduction of bismuth powder
The traditional production methods of bismuth powder include water mist method, aerosol method and ball milling method; When atomizing and drying in water by water mist method, bismuth oxidation is easily caused by the large surface area of bismuth powder; Similarly, under high temperature, the contact of bismuth with 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 to manually hammer the bismuth ingot with stainless steel to ≤ 10mm bismuth particles, or to quench bismuth with water. Then the bismuth particles enter the vacuum environment and are crushed by the ball mill lined with ceramic rubber. Although this method is used for ball milling in vacuum, it has less oxidation and low impurities, but it is time-consuming, low yield, high cost, and the particle size reaches 120 mesh, which affects the product quality. The invention patent CN201010147094.7 provides a production method of ultra-fine bismuth powder, which is produced by wet chemical process, with large production capacity, short contact time with oxygen during the whole production process, low oxidation rate, less impurities, oxygen content of bismuth powder 0 ＜ 0.6, and uniform particle distribution; Particle size - 300 mesh.
1) Preparation of bismuth chloride solution: take the bismuth chloride stock solution with a density of 1.35-1.4g/cm3, and add acidified pure water solution containing 4% - 6% hydrochloric acid; The volume ratio of acidified pure water solution to bismuth chloride stock solution is 1 ∶ 1-2;
2) Synthesis: adding zinc ingot with clean surface to the prepared bismuth chloride solution; Start displacement reaction; Observe the reaction end point. When the reaction end point is reached, take out the undissolved zinc ingot and precipitate for 2-4 hours; The observation and judgment basis of the reaction end point is: there are bubbles in the solution participating in the reaction;
3) Separation of bismuth powder: extract the supernatant of the precipitate in step 2) to recover zinc by conventional method; The remaining precipitated bismuth powder is stirred and washed for 5-8 times with acidified pure water solution containing 4% - 6% hydrochloric acid, and then rinsed with pure water until the bismuth powder is neutral; After quickly drying the bismuth powder with a centrifuge, immediately soak the bismuth powder with anhydrous ethanol, and then dry it;
4) Drying: send the bismuth powder treated in step 3) to a vacuum dryer with a temperature of 60 ± 1 ℃ for drying to obtain - 300 mesh bismuth powder finished products.
The bismuth powder produced by the above process has the advantages of high purity and fine particle size; Therefore, the oxidation rate is low.