I have something I want to remove rust from, so I have been thinking about sand blasting. Thus, this thought popped into my head: how spectacular would it be to use aluminum powder? (To be clear, I am not going to try this.)

My wife’s reaction to this was “You guys…” but I know she would absolutely want to watch if someone was going to try it.

I suspect you would need much more kinetic energy to get a thermite reaction going than the aluminum powder in a sand blaster.

Does the second rusty ball really need to be a rusty ball since it is covered in foil?

Might improve the odds of reaction to have iron on both sides? Would the reaction also work if both balls were covered in foil?

Doubles the reaction.

that brings childhood memories. Not too microscale though. Rust was everywhere in USSR. Small buckets of rust, small buckets of aluminum powder. When we experimentally discovered the reaction - we were too young still for school chemistry lessons - it was "microscale" - we burned a hole in the kitchen table in my friend's apartment (like a true hero he told his parents that he was alone and received the punishment :) We also tried to make a rocket using the mix as the rocket fuel - it burned the whole rocket like a huge firework :)

Great laugh at end of micro demo video.

Please try this at home. You all have rusty iron ball laying around, right?

It wouldn't be weird for someone in the south of France to have a rusty pétanque ball.

Now you can be hoisted not just in your own petard, but also in your own pétanque.

This clearly calls for thermite petanque.

Certainly a ball peen hammer that could be encouraged to go rusty for scientific purposes. I wonder if it would work well enough striking a sheet of aluminum foil on a hard flat surface?

Hammer faces would work (def wear goggles!!!). Hit the face of the disposable one with a mixture of hydrogen peroxide, vinegar and salt and wait an hour.

Joining the thread to see where iron balls can be sourced.

Some vendor on AliExpress? Those Lucky Iron Fish?

Cast iron pan left outside for a day or two.

This might work with old iron dumbbells (or modern iron kettle balls if left unpainted). Your gym might hate you for it though.

I'd guess exact form wouldn't matter. Wrap a hammer in foil and beat up something rusty.

Based on the title I was expecting to see “energetic materials”, which are carefully engineered variants of thermite.

For example, alternating layers of aluminium and iron oxide can be deposited in the same manner as seen in chip production by evaporating the materials in a vacuum chamber.

This allows layers tens of nanometers thin, essentially a perfect mixing and a very intimate contact between the reactants.

Some of these materials have far more bang per unit mass than conventional explosives.

wow I hadn't heard of this but it's quite cool. aka Nano-Thermite

https://en.wikipedia.org/wiki/Nano-thermite

Titanium-Boron nano thermite is easily the most SciFi thing I have read today, and apparently Aluminum-Teflon nano thermite is also a thing.

Does the ball need to be iron? Can we just take a 3d printed sphere, paint it with glue ,roll it around in a bucket of rust and then smash?

I would guess you need something rigid and dense to generate enough pressure, though I don’t know if that rules out your suggestion. It does not have to be a ball.