Can Coarse Aluminum Flake be Used in a Thermite Reaction?

[pearbear21]

Your thorough examination of thermite that has been brought up numerous times makes me apt to come to you for some discussion/answers. I've seen all the mentioned iron oxide making processes, but I have yet another I'd like checked and thought through. What if I did the following...

acid steel wool a salt... hydrogen gas?
2HCl + Fe --> FeCl2 + H2(g)

and then after dissolving all of the iron in the HCl, I'd do this with some quite impure Sodium Hydroxide. (The purity of NaOH shouldn't matter, since I can wash the iron oxide in water or alcohol.)

FeCl2 + 2NaOH --> Fe(OH)2 + 2NaCl

To get rid of the NaCl, all I'd have to do is wash the precipitate. I realize that I still have Iron Hydroxide, not Iron Oxide. In theory, wouldn't that actually WANT to oxidize further with ambient air to form Fe2O3? If so, great. There's an easy and fast way to make one of my reactants, if it will work.



I do have one more question. I have have some VERY pure aluminum flake. It's about -20+30 mesh or so. Seems like that would be too coarse for a thermite reaction. I haven't tried it yet, but I know that I've never seen aluminum this coarse used in an aluminoferrite reaction. Can anyone think of a way to use it for this reaction? I have exactly one pound of it.

 

[mrjeffy321]

Wow, I am famous.

I have seen this method of making Iron Oxide only recently, and have never tried it before myself, but in theory it should work.

With the Iron (II) Chloride you get from adding HCl to steel wool,
Fe2+ salt + O2 + OH- ----> Fe2O3.xH2O
so first you make the Iron Hydroxide, and then use the oxygen from the air to make it into Iron Oxide.

You could also do it, (easier), with Iron (III) Chloride,
Fe3+ salt + OH- ----> Fe2O3.xH2O
this way you wouldn't need any oxygen from the air, it would be done in once step insted of 3 (once you get the FeCl3 that is).

A quote from another site describing the same method,

A faster way to make iron oxide for thermite is to dissolve the nails in some acid, then add a base such as sodium hydroxide to precipitate iron hydroxide. This precipitate can then be washed several times and heated to make iron oxide suitable for thermite. I have used this method before and it works.

If you do try this method, I would be interested to know how it goes. I think using the one step bleach method to oxidize steel wool is pretty simple though.

From my original experimentation with thermite, using aluminum can shavins as the aluminum for the reaction, it failed because I can now assume either the aluminum wasnt pure enough, it was too course, or both. Now that I have some very fine Al powder (I think 200 mesh), my thermite works very well. I think your course aluminum powder might workm, in theory, once the thermite gets started, but it will be hard to light it. If you would find a way to increase the surface area to volume ratio on the aluminum flakes, that would help get the reaction started.

 

[pearbear21]

I have a batch of each method reacting right now. The bleach is super-fast... didn't realize that. The other is a lot of work, actually. Looks like it's working though. I have a nice precipitate forming, but it took forever to complete the first step of reacting one pad of steel wool in HCl.

About the aluminum... that's a tough one. I really am at a loss as to how I could increase it's surface area. I have no rock tumbler, but I highly doubt that would do much, even if I used some large lead balls (actually I could just use some .45ACP bullets... I reload my own shells). So, aluminum is pretty malleable. If I can't make it into a smaller mesh, I theorize that I might be able to pound on it, which would flatten it. In turn, more surface area. Hmm.

I can tell that the Iron Oxide is going to be simple. Now it's a matter of working on my aluminum. I've read that a pretty coarse mesh is to be desired in a lot of cases, because it makes the thermite burn longer (though more difficult to ignite).

Anyone with ideas on the aluminum PLEASE speak up.

 

[Gokul43201]

Ball milling works on aluminum powder. Try it.