Wet silicon powder catches fire spontaneously when mixed with dilute acid! ! !
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This post was last edited by BIERGAI on 2009-10-28 at 23:02. I earnestly hope that those with more experience can help analyze this situation: When silicon powder that has been washed is mixed with dilute acid in a humid environment, it catches fire spontaneously. The combustion is not intense, and the temperature is not very high; the flame appears blue and red. The P content of the silicon powder was only a few ppm before the reaction, and gas was released during the reaction; please help analyze this. Thank you! ! !
May I ask the original poster, what acid was used? It seems to be a strongly oxidizing acid; it releases a large amount of heat when it comes into contact with water, and the amount of acid added isn’t very large. How is the odor of the released gas? The particle size of the silicon powder in your case is very small; silicon powder with such small particles has high reactivity, and it burns when exposed to large amounts of heat. When conducting such experiments, it’s best to be cautious; it’s ideal to do them in a fume hood on a test bench! If necessary, the reaction gases can be collected and analyzed by GC.
Silicon powder is very fine; it’s acidic, hydrochloric acid. As for what the gas is, that’s not quite clear
The acid concentration isn’t high, so the amount of heat released should not be significant. Please ask the person on the 2nd floor to analyze it further
Hydrochloric acid should not be able to cause scaling and burning.
This is strange; in the past, when we used a very dilute hydrofluoric acid solution (40% hydrofluoric acid diluted tenfold) to clean the silicon powder deposits inside the reactor, there were also flames and explosions... We’ve never been able to figure out what reaction was taking place
Friend on the 2nd floor, could you explain in more detail why \"silicon powder with a fine particle size has high reactivity and burns when exposed to large amounts of heat\"? Thank you very much! ! !
Hydrochloric acid is fine; there will be no reaction. (I’ve done experiments) The original poster must have added another acid. Of course, it will also react if an alkali is added. 6. Leakage: Microsilica powder adheres to the inner wall of the furnace; when it comes into contact with 4HF, H2 is generated, and H2 may accumulate. This reaction is exothermic, resulting in local high temperatures that cause the combustion of H2 and localized popping sounds. Si+4HF ===SiF4+2H2
It can be determined that it is hydrochloric acid, with a concentration of around 10 percent. A natural phenomenon occurred during the addition process, and this phenomenon persisted for a long time; after stirring for a while, the reaction stopped. Please analyze it thoroughly; thank you very much!
I don’t know that much. I’m glad everyone can discuss together. “For silicon powder that is washed with water, it should first be pickled with acid and then washed with water; this is a practice used abroad, with the aim of reducing the content of metallic impurities in the silicon powder. When dilute hydrochloric acid is added to water, it also releases a large amount of heat; as for combustion, it’s not quite clear. Additionally, someone on the 6th floor mentioned that burning and explosions occurred during the cleaning of the bell jar. The accumulation of hydrogen is likely caused by amorphous silicon; its formation seems to be inevitable. Amorphous silicon is silicon that has absorbed hydrogen, and it has numerous pores, which makes it easy for hydrogen to accumulate and lead to burning or explosions when cleaned with hydrofluoric acid.
Oh.........I’ve heard of the idea of hydrogen being enriched within amorphous silicon for the first time... Maybe so....