Fine & light particels dropped down in vacuum

[ravindrar]

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.

 

[PietKuip]

Probably static electricity.

 

[ravindrar]

Probably static electricity.

 

[ravindrar]

May you explain. How static electricity generated.

 

[PietKuip]

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.)

 

[ravindrar]

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.)

 

[ravindrar]

Thanks, as you said it must be touch and not friction. Material is already dry and walls are of SS metal.

 

[sophiecentaur]

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.

 

[ravindrar]

Thank you. May I use negative Ion generator? What if silo is grounded?

 

[sophiecentaur]

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.