Date: Fri Feb 16 05:50:40 2007

Author: Sam Sampere

Subject: Re: Van de Graaffs

Post:
Al sputters quite easily. I was joking about the Al film inside the
column though. Sorry.

You're right about the Al2O3. It's a very tough oxide and that's the
reason Al doesn't 'rust' like iron. It is a self limiting and coherent
film on the surface of Al. This film prevents further penetration of
oxygen. But it's pretty thin, too.

Sam

-----Original Message-----
From: tap-l-owner@lists.ncsu.edu [mailto:tap-l-owner@lists.ncsu.edu] On
Behalf Of Bernard Cleyet
Sent: Thursday, February 15, 2007 7:04 PM
To: tap-l@lists.ncsu.edu
Subject: Re: [tap-l] Van de Graaffs

Huh?

I thought Al was particularly resistant to sputtering; I suspect because

of the tenacious oxide surface. Also I wouldn't expect much sputtering
at atmospheric pressure.

bc, advised to use al electrode while sputtering for the above reason.

Sam Sampere wrote:

>Funny how these VdG comments and questions come up at this time every
>year.
>
>Which end of the tribo series is Teflon on? I don't remember and I'm
too
>lazy right now to look it up. I spent 2 hours shoveling last night, my
>back hurts and I'm tired.
>
>Anyway, make sure that Teflon is towards the negative end of that
>series. It would be silly to make rollers out of materials very close
to
>each other.
>
>Aluminum is right in the middle, or neutral, so that's a safe bet. I
>don't really like Al because it sputters easily. I can envision the
>inside of the column of the VdG coated with an Al film. That's a short
>right back to ground.
>
>Sam
>
>
>
cut


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