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Author: Subject: Screens for Aluminum Powder
JJay
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Screens for Aluminum Powder

I've been wanting to try out some exotic thermites. I have a small rock tumbler and some blenders that won't be missed if I accidentally burn out the motors. I know I can use simple equipment to grind aluminum, but I think the particle size is important for producing thermites. I see a few types of screens available on eBay and Amazon, but I'm not exactly sure how hard they are to use or how large of a screen is required to grade aluminum reasonably quickly.

What kinds of screens do people use for grading their aluminum powder produced from grinding aluminum in a ball mill or blender? Will I need a large screen to grade appreciable amounts of aluminum?
OldNubbins
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I tried milling my own aluminum powder from scrap chips and turnings since I have plenty of those but it was so tedious that I gladly bought the prepared stuff, and I am a horrible cheapskate. However, I have found that mixing in some courser material to supplement the mix works well as long as there is enough fine powder to get the reaction initiated. It also seems that I get more yield improvement from larger batches (go big or go home kinda thing) rather than particle quality/size but that's based on absolutely no data at all.
Herr Haber
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Ideally for dealing with large quantities you'd need a shaker and a set of sieves. For thermite the size is so small it always needs a bit of help to fall down the screens.
You can probably use a spoon to force particles through the mesh if the amounts required are low.

The spirit of adventure was upon me. Having nitric acid and copper, I had only to learn what the words 'act upon' meant. - Ira Remsen
JJay
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I see quite a few laboratory sieve shakers on eBay. They're not cheap. I also see shakers that are apparently designed for kitchen use....

I'm not sure I want to drop $1000 on a lab shaker... I was hoping there would be some kind of manually operated shaker that I could use for making a couple hundred grams of aluminum powder.... S.C. Wack bibliomaster Posts: 2267 Registered: 7-5-2004 Location: Cornworld, Central USA Member Is Offline Mood: Enhanced I'm not sure how producers sift 325 mesh Al or even if they do, but if they do it isn't with big versions of test sieves and test sieve shakers, which AFAIK is strictly an analytical lab toy. Something using pressure differential to force the powder through would be really helpful. You could simply buy small pieces of screen and rig something up to suck Al suspended in petroleum ether through. "You're going to be all right, kid...Everything's under control." Yossarian, to Snowden RogueRose International Hazard Posts: 1573 Registered: 16-6-2014 Member Is Offline I'm in the process of building seives and a shaker. Building a shaker is actually very easy, you can use just about any motor. think about how your cell phone vibrates. You mount a off-centered weight on the shaft of a motor and as it spins, it shakes (or vibrates), as the off-centered weight moves from one side to the other. There are many ways to do this and all can be very simple. Or you could use something like an old reciprocating saw (sawzall) that will shake the seive base back and forth. I orderd 6 different screens, all 12" x 12", all SS from mesh 10 down to 500 which may be too small to be practical (my other small sizes are 325 & 400). I think I got all of these for about$30-35, and 4 of them were from China (only took 7-14 days to arrive actually!)

The problem I'm facing now is do I build square seives and use the full surface area or do I go with round ones. They are all going to be stackable. I was thinking of using 5 gallon buckets as the wall and cut them to about 2-4" high, depending on the mesh size. If I make them square, I think I'll have to make them from wood but I may epoxy coat them to make them more easily cleanable.

Any suggestions or comments on the shapes would be appreciated. I'll post up pics of how I put things together and how I build the shaker if anyone is interested.
JJay
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 Quote: Originally posted by RogueRose I'm in the process of building seives and a shaker. Building a shaker is actually very easy, you can use just about any motor. think about how your cell phone vibrates. You mount a off-centered weight on the shaft of a motor and as it spins, it shakes (or vibrates), as the off-centered weight moves from one side to the other. There are many ways to do this and all can be very simple. Or you could use something like an old reciprocating saw (sawzall) that will shake the seive base back and forth. I orderd 6 different screens, all 12" x 12", all SS from mesh 10 down to 500 which may be too small to be practical (my other small sizes are 325 & 400). I think I got all of these for about \$30-35, and 4 of them were from China (only took 7-14 days to arrive actually!) The problem I'm facing now is do I build square seives and use the full surface area or do I go with round ones. They are all going to be stackable. I was thinking of using 5 gallon buckets as the wall and cut them to about 2-4" high, depending on the mesh size. If I make them square, I think I'll have to make them from wood but I may epoxy coat them to make them more easily cleanable. Any suggestions or comments on the shapes would be appreciated. I'll post up pics of how I put things together and how I build the shaker if anyone is interested.

That's a pretty cool project. I was thinking of doing the same thing but with square trays... not sure if square or round is better.... I guess it depends on the pattern the trays follow when they shake.
S.C. Wack
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Some experiment in producing separation machinery should test a design that is actually used. Industrial vibrating screens are nothing like test sieve shakers; they may be available at 100 mesh or finer but good luck. Other dry methods don't use screens.

If you have problems getting material through a screen, and for most things you will past 200 mesh, shaking will help but do not overestimate how much.

"You're going to be all right, kid...Everything's under control." Yossarian, to Snowden
charley1957
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I also wanted to do some exotic thermites. After looking into ball milling and all that, because I’m so cheap and because I can build almost anything, the decision to buy the aluminum powder was a hard one. I’ve never regretted it a minute, and all that time spent tinkering with some machine was much better spent doing chemistry. If you consider your time worth anything, you’ll be way ahead just buying it. (I can’t believe I just wrote that.)

...it has often proved true that the dream of yesterday is the hope of today and the reality of tomorrow.

Robert H. Goddard

 Sciencemadness Discussion Board » Fundamentals » Beginnings » Screens for Aluminum Powder Select A Forum Fundamentals   » Chemistry in General   » Organic Chemistry   » Reagents and Apparatus Acquisition   » Beginnings   » Responsible Practices   » Miscellaneous   » The Wiki Special topics   » Technochemistry   » Energetic Materials   » Biochemistry   » Radiochemistry   » Computational Models and Techniques   » Prepublication Non-chemistry   » Forum Matters   » Legal and Societal Issues   » Test Forum