[labnetwork] Titanium hazard

[Bernard Alamariu]

Hello,

The Titanium is a chemical active element used in high vacuum Ion Getter 
Pumps; it could accumulate
a high volume of gas, which by a sudden expansion could generate the 
necessary flame temperature
for some gases.
The scraped material from the e-beam walls could have contained in 
addition to Ti some other highly
oxidizing elements like Al, Cr ( actually they were used in Napalm 
fabrication) and also Pt which coverts
the molecular H2 into atomic Hydrogen ( with low temperature ignition 
point), etc
I think the flame is triggered by a such thermodynamic/ chemical 
process; not by static electricity, as
it happened in a metal garbage can, too.
Thanks, Bernard


On 5/7/13 9:47 AM, Joe Palmer wrote:
> 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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