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A method for producing ultrafine bismuth powder

wallpapers News 2021-05-14

Bi molecular formula, molecule 208.98; Bismuth powder belongs to non-ferrous metal powder, and its character is light gray. Its use is very wide, mainly used in the preparation of bismuth products, bismuth alloy and bismuth compounds.
The traditional production methods of bismuth powder include water mist, gas atomization and ball milling. When atomizing and drying in water, the bismuth powder is oxidized easily due to the large surface area of bismuth powder. Similarly, at high temperature, the contact between bismuth and oxygen is easy to cause a lot of oxidation. Both methods result in many impurities, irregular shape and uneven particle distribution of bismuth powder. In the ball milling method, the bismuth ingot is manually hammered with stainless steel to the bismuth granules ≤10mm, or the bismuth is quenched with water. The bismuth granules are then crushed by a ball mill lined with ceramic rubber in a vacuum environment. Although the ball mill in vacuum has less oxidation and low impurities, this method is time-consuming, low yield and high cost. The coarse particle reaches 120 mesh, which affects the quality of the product.

A production method of ultrafine bismuth powder is performed as follows:
1) Preparation of bismuth chloride solution: take the original solution of bismuth chloride with a density of 1.35-1.4g /cm3, and add the acidified pure water solution containing 4%-6% hydrochloric acid; The volume ratio of the acidified pure water solution and the original bismuth chloride solution is 1:1-2.
2) Synthesis: add zinc ingot with clean surface into the prepared bismuth chloride solution; Start the substitution reaction; The end point of the reaction was observed. When the end point of the reaction was reached, the undissolved zinc ingot was taken out and deposited 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: the supernatant of step 2) precipitate is extracted to recover zinc by conventional methods; The remaining precipitated bismuth powder was washed 5-8 times with the acidified pure water solution containing 4%-6% hydrochloric acid, and then rinsed with pure water until the bismuth powder was neutral. After drying the bismuth powder by centrifuge, the bismuth powder was soaked in anhydrous ethanol and then dried.
4) Drying: The bismuth powder treated in Step 3 was sent to a vacuum dryer with a temperature of 60 SRC to be dried, and -300 mesh bismuth powder was prepared.
The purity of bismuth powder produced by the above process is 99%. The particle size is extremely fine and can reach -300 mesh. The measured chemical composition of the bismuth powder prepared by the invention is as follows: Bi Bb 099, Fe < 0.1, O < 0.5, Bio < 0.1, Cr < 0.01, Cu < 0.01, Si < 0.05, and other impurities < 0.18; At the same time, because of the zinc ingot replacement process, chemical reaction only involves the dissolution of zinc and bismuth precipitation, avoiding the disadvantages of a large number of chemical gas generation, reduce the pollution to the environment and harm to human body. Compared with the prior art, the whole process of the invention is only in short time contact with air in the centrifuge spin-drying, and all the other processes have reaction liquid or anhydrous ethanol, or vacuum isolation with oxygen, so the oxidation rate is low.

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