I used SS balls and container and sealed the container in Ar atmosphere. After ball mill, there is particle size reduction but I see sparks with very high exothermic oxidation. It is quite scary. Can we tune somehow or add something to make it safer.
One thing I found in the literature is use some carbon source like coal to coat the freshly formed Al surface to avoid oxidation. It didn't work for me. There is also an increase in the weight of the material due to oxidation.
Need some help to avoid the instant oxidation?
After grinding under argon, the surface of the aluminum particles is oxide-free and oxidizes very actively as soon as you open the ball mill. For this reason, you are not allowed to open the ball mill normally. Instead, after grinding, you should let the air into the ball mill via a valve with very small portions. Each additional portion of air oxidizes the powder a little more, but the heat development does not become critical. After several portions of air, the particles no longer oxidize and the powder becomes stable. Only now can you open the ball mill.
Dear Mr. Gandharapu
We are producing aluminum power, the first part is making the metal powder by atomizing molten aluminum by air through a nozzle. the second part is grading the powder to separate the wanted particle size, then using the ball mill to produce the flake powder.
Milling of powder is done with carbon steel and stainless steel balls. The grinding uses mineral spirit and lubricating agent, so there is no spark and no oxidation.
If you want to use argon gas in milling aluminum powder you must add oxygen as 8-10% to the stream of argon or even nitrogen gas to control the oxidation and prevent the explosion of the mill.
by the way, there is no particle size reduction as a goal of the milling of aluminum powder, the name is flaking the aluminum powder with some edge broken of the particles as a result of milling action (impact + attrition + share force) inside ball mill
Pranay Gandharapu it seems you are opening the jar right after grinding. Allow adequate time to the jars after ball milling as right after grinding there will be more significant heat developed and also there is argon gas purged. if you open the jar right after grinding the powder will be oxidized of it can catch fire quickly. as mentioned by Vadim Verlotski either release the argon gas slowly or allow some time in hrs after grinding and then open the jar will reduce the severe effects.
To this I would add, whether oxide or nitride or even carbide, there is ought to be some weight increment as gaseous products are trapped into solid paticles outer protective surface. If you want absolute purity, keep you powders under argon always. If not possible, use hexane or other suitable alkane/alkene to cover the metal. Add in excess so that no metal-hexane slurry rather yhan aluminium powder deposited below hexane is observed.
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