[labnetwork] Titanium hazard

[Joe Palmer]

All,

When fine particles of a metal that can oxidize (Ti, Al, Cr, Fe, Ag, 
etc) are suddenly exposed to air, they of course do oxidize, and because 
their surface area to volume ratio is so great they can reach the 
ignition temperature of acetone, methanol, or isopropanol, and in some 
cases their own ignition temperature.  This is similar, but not 
identical to the mechanism behind grainery explosions. While water is 
generally anathema to vacuum systems, in this case wiping the material 
down with water or a mixture of water and isopropanol, is not a bad idea.

Regards,

Joe Palmer
PRISM MNFL
Ops Manager

On 5/6/2013 4:08 PM, Leif Johansen wrote:
>
> Hello Rick,
>
> At DTU Danchip we have an e-beam evaporation system in which we 
> deposit Titanuim. We have had at least three incidents of wipes or 
> other parts catching fire during maintenance work. I do believe that 
> the root cause is that Titanuim oxidizes very fast, especially when a 
> large, fresh surface is exposed to oxygen.
>
> I have tried to translate our safety precautions from Danish into some 
> sort of English:
>
> "Before the work is started, DI water is filled in a bucket and placed 
> next to the machine. Surface cleaning of various chamber parts must 
> take place over the water bucket. All used cloths, with or without 
> Ethanol/IPA are also to be deposited in the bucket, so they can absorb 
> water.
>
> Absorption of water in the cloths will prevent ignition. Some metals, 
> like Titanum, when exposed to mechanical stress like hammering or 
> scraping, form small particles which ignite as a result of fast oxidation"
>
> Hope this could help.
>
> Best regards,
>
> Leif
>
> *From:*labnetwork-bounces at mtl.mit.edu 
> [mailto:labnetwork-bounces at mtl.mit.edu] *On Behalf Of *Morrison, 
> Richard H., Jr.
> *Sent:* 6. maj 2013 15:50
> *To:* labnetwork at mtl.mit.edu
> *Subject:* [labnetwork] Titanium hazard
>
> Hi Everyone,
>
> Last week one of the staff was wiping off some evaporator parts that 
> were covered with Titanium metal. He was using texwipes soaked with 
> IPA. He tossed the texwipes in the trash then accidentally dropped 
> some wipes saturated with IPA on top of them and a fire started. It 
> self extinguished after 1 minute but it melted the bottom of a plastic 
> trash can.
>
> Have any of you had that happen or something similar? Needless to say 
> this is very alarming and I need to understand what could have caused 
> this and develop a corrective action plan.
>
> Rick
>
> Draper Laboratory
>
> Group Leader Microfabrication Operations
>
> 555 Technology Square
>
> Cambridge Ma, 02139-3563
>
> www.draper.com <http://www.draper.com>
>
> rmorrison at draper.com <mailto:rmorrison at draper.com>
>
> W 617-258-3420
>
> C 508-930-3461
>
>
>
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