Fine & light particels dropped down in vacuum

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Discussion Overview

The discussion revolves around an experiment involving the behavior of low-density powder particles dropped in a vacuum chamber. Participants explore the reasons for the observed dust cloud instead of straight downward motion, focusing on the role of static electricity and other factors affecting particle behavior in a vacuum environment.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant describes an experiment where low-density powder created a dust cloud when dropped in a vacuum chamber, questioning why it did not fall straight down.
  • Some participants propose that static electricity may be responsible for the behavior of the powder particles.
  • There is a discussion about how static electricity is generated, with mentions of friction and the interaction between particles and surfaces.
  • Another participant suggests that electrostatic induction is a significant factor in static buildup, rather than friction.
  • A suggestion is made to use a source of ions in the chamber to discharge the particles, comparing it to the role of water droplets in ordinary situations.
  • Questions arise about the effectiveness of using a negative ion generator and the implications of grounding the silo.
  • One participant mentions the possibility of using an AC discharge with RF excitation to produce ions around the particles.
  • There is a suggestion to conduct further research using online resources to find informed sources on the topic.

Areas of Agreement / Disagreement

Participants express differing views on the mechanisms behind static electricity generation and its effects on particle behavior. There is no consensus on the best method to mitigate the issue of static buildup.

Contextual Notes

The discussion includes assumptions about the materials involved and the conditions within the vacuum chamber, which may influence the generation of static electricity and particle behavior.

ravindrar
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I did a experiment. I made a vacuum chamber with a silo on the top. Also provided the butter fly valve between vacuum chamber & silo. Filled the silo with low density powder say 0.2 gm / cc. Created vacuum in silo having powder and vacuum chamber. When I dropped this powder in vacuum chamber some powder did not travel straight down there was dust cloud. Why it did not travel straight as there was no air resistance. May anyone has answer.
 
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Probably static electricity.
 
PietKuip said:
Probably static electricity.
 
May you explain. How static electricity generated.
 
ravindrar said:
May you explain. How static electricity generated.
By friction. Friction between the particles in the powder, friction between particles and the walls. The walls may also get charged. It depends on materials, on humidity, etc. But in a vacuum, everything becomes dry.

(And it is not really friction, it is touching and separating that transfers electrons between surfaces.)
 
PietKuip said:
By friction. Friction between the particles in the powder, friction between particles and the walls. The walls may also get charged. It depends on materials, on humidity, etc. But in a vacuum, everything becomes dry.

(And it is not really friction, it is touching and separating that transfers electrons between surfaces.)
 
Thanks, as you said it must be touch and not friction. Material is already dry and walls are of SS metal.
 
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Powder particles are the very devil to handle because the electric forces are similar to their weight. Static build up is a big risk and it usually happens due to Electrostatic Induction, rather than the old favourite Friction. I think a way to deal with this problem may be to have a source of ions in your chamber, to discharge the particles. It would do the job that water droplets do in ordinary situations.
 
Thank you. May I use negative Ion generator? What if silo is grounded?
 
  • #10
ravindrar said:
Thank you. May I use negative Ion generator? What if silo is grounded?
I don't know which would be better. If your vacuum were not too deep, you could, perhaps just use an AC discharge using RF excitation which would produce both polarities of ion all around your particles.
Actually, this seems to be pretty specialised stuff. Have you done the normal google search? You could get some well informed sources if you choose the right search terms.
 

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