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Author: Subject: Polar Coating
encipher
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[*] posted on 16-1-2007 at 12:32
Polar Coating


Hi,

I have a vial that contains ferrofluid suspended in a kerosene solution. I want to seal the vial and perhaps give it to a friend of mine to 'play with'. The problem arises when the vial is moved or shaken, or a magnet is brought close. It becomes coated with the ferrofluid (black) and then nothing on the inside is visible, it sticks to the inside of the vial, which is glass. Is there any coating I can use to coat the inside of the vial with such that all the kerosene based ferrofluid will not stick to the sides of the vial?

Thanks.




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[*] posted on 16-1-2007 at 13:13


Teflon?

Wait, that doesn't stick to a damned thing.

Ooh, silicone rubber?




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encipher
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[*] posted on 16-1-2007 at 15:00


It should be a clear coating, otherwise it would beat the whole purpose.



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[*] posted on 16-1-2007 at 15:28


Hmm.

The surface of non-silanized glass is polar, specifically from the silanol (Si-OH <--> Si-O-) groups. It appears that either your glass is treated or, more likely, you are seeing a by-product of the fact that nano particles are quite "sticky". I am not sure how to passivate a polar surface vs. "nano-sticky" effects. I'll poke around a bit and get back to you (I know sonication is frequently employed to keep the particles from aggregating).

Cheers,

O3




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[*] posted on 17-1-2007 at 08:10


Soaking glass in a strongly basic solution will make the surface hydrophilic by changing its composition from Si - O - Si to Si - OH. I don't know how much that would help here, though.



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