# Powdering aluminum chemically?

I need a fine aluminum powder for many reactions/experiments. Could I dissolve the metal in an acid and then drop it out of solution using a base, or vice versa? What would be the best chemicals/process to produce a high yield of aluminum powder?

• could you explain the chemicals needed/produced in the reaction? other than aluminum metal of course – Eli E. May 14 '16 at 17:23
• Burn glucose in your muscle cells and actuate a file. ;-) – aventurin May 14 '16 at 17:27
• I already have aluminum filings that i want to convert into a finer powder. For example: I tried making thermite with the filings but couldn't get it to oxidize, my guess is the surface area is too low still for the aluminum to react with the finer iron-oxide powder. – Eli E. May 14 '16 at 17:35
• There is no realistic way to produce aluminium powder at home. You should stick with buying it. There are some work-arounds for magnalium, but I don't recommend it. Aluminium powder is commercially available. There are several grades with varying grain sizes. I recommend to buy a coarse one (maybe even granules) for chemical experiments and one of the finest for aluminotermia experiments. – permeakra May 14 '16 at 18:13
• "Could I dissolve the metal in an acid ..."? Yes, and produce one liter of hydrogen per gram. – Karl Jan 2 '19 at 9:05

## 1 Answer

There is no simple and affordable way to obtain fine aluminium powder chemically. As permeakra said, in the absence of a ball mill, it's just easier to buy some.

Note that a finely dispersed aluminum powder obtained commercially is always going to have low level of impurities such as $$\ce{Fe, Mn, Si, Mn}$$ (from the grinder's balls) and traces of wax/fats on the surface (added by manufacturer on purpose to prevent adhesion and separate particles from each other).

As for the chemical/physicochemical methods, there is a great overview included in the US5885321A patent, among which there are the following:

• exploding of aluminum wire in a vacuum by a high electric current (particles' size varies a lot);
• condensation of vaporized aluminum in a current of inert gas (very energy-inefficient);
• decomposition of aluminium carbonyls (there is no experimental evidence for any of these to exist);
• reduction of halides in solution (issue with separation of the particles from the salts);
• CVD of aluminium thin films by decomposition of tertiary amine complex of aluminum hydride (complex multistep process with low yield and expensive and volatile precursors);
• decomposition of the dialkylaluminum hydride in $$\ce{H2}$$ atmosphere at elevated temperatures (up to $$\pu{260 °C}$$) with a catalyst ($$\ce{Ti, Zr, Hf, Ln}$$) and a tertiary amine (no particle size control, questionable efficiency);
• decomposition of diethylhydridoaluminum or diisobutylhydridoaluminum in diisopropyl ether or triethylamine at $$\pu{90 °C}$$ to $$\pu{185 °C}$$ with titanium isopropoxide catalyst.

The patent itself proposes

decomposing alane-adducts in organic solvents under an inert atmosphere to provide highly uniform particles selectably sized from about $$\pu{65 nm}$$ to about $$\pu{500 nm}$$

where adducts are

trialkyl amines and tetramethylethylenediamine, ethers and other aromatic amines;

and conditions such as

atmospheric pressure and at temperatures as low as $$\pu{50 °C}$$ with xylene solvent, ... , toluene, dioxane, and tetramethylethylenediamine.

As a catalyst, titanium halide, amide and alkoxide are used. Authors also provide a complete table of the systems tested:

### References

1. Higa, K. T.; Johnson, C. E.; Hollins, R. A. Preparation of Fine Aluminum Powders by Solution Methods. US5885321A, March 23, 1999. (PDF)