- #1
beion
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I recently had some discussions about the use of aluminum in a ultra-high vacuum (UHV) apparatus. There seem to be those who believe Al is good in UHV and those who believe it is bad. I was wondering if anyone has some authoritative source for information on this.
Those who believe it is bad seem to say the oxidization of machined Al creates pores that can trap junk that then spoils the vacuum. On the other hand, I always thought it was the tight, tenacious oxide that makes Al good in a vacuum. I've heard that anodized Al, due to its thicker oxide, is good for UHV. And I have heard that anodized Al, due to its thicker oxide, is bad for UHV. I tend to think anodization will lead to a more porous surface and thus larger surface area, which is bad, but I don't actually know that. I have also heard that you can do a special treatment on Al to make it good for UHV, but no one seems to know what that treatment is.
In my own personal experience, I have used regular machined Al, cleaned as per standard UHV cleaning techniques (Alconox soap, acetone, IPA, N2 blow dry), in a vacuum system that achieved 10^-11 Torr. So, it can't be too bad.
What do you think?
Those who believe it is bad seem to say the oxidization of machined Al creates pores that can trap junk that then spoils the vacuum. On the other hand, I always thought it was the tight, tenacious oxide that makes Al good in a vacuum. I've heard that anodized Al, due to its thicker oxide, is good for UHV. And I have heard that anodized Al, due to its thicker oxide, is bad for UHV. I tend to think anodization will lead to a more porous surface and thus larger surface area, which is bad, but I don't actually know that. I have also heard that you can do a special treatment on Al to make it good for UHV, but no one seems to know what that treatment is.
In my own personal experience, I have used regular machined Al, cleaned as per standard UHV cleaning techniques (Alconox soap, acetone, IPA, N2 blow dry), in a vacuum system that achieved 10^-11 Torr. So, it can't be too bad.
What do you think?