I recently successfully made thermite from iron oxide powder and aluminum powder. However, I have a couple of questions about copper and iron oxides.

The kind of iron oxide that is made by electrolyzing iron in a salt water bath. You rinse the solution well to get some of the salt out then boil off/dry the remaining sludge. What is left is a red powder. What kind of iron oxide is this? (II,III)

Lastly, if I repeated the same process with copper, would I get copper(I) oxide or copper(II) oxide?

Apologies for my lack of knowledge in chemistry.

  • 1
    $\begingroup$ Iron(I) and iron(IV) oxides do not exist. The only iron oxide with a reddish color is iron(III) oxide $\ce{Fe_2O_3}$. Iron(II) oxide FeO is not stable in air. It gets quickly transformed into iron(III) oxide. The thermite reaction works well with aluminum powder and iron(III) oxide. $\endgroup$ – Maurice Jul 12 '20 at 19:44
  • $\begingroup$ Copper oxides are nowhere near as stable as aluminum oxides. $\endgroup$ – Jon Custer Jul 13 '20 at 18:15
  • $\begingroup$ @Maurice $\ce{FeO}$ oxidizes to black $\ce{Fe3O4}$, not to red/brown $\ce{Fe2O3}$, as the former is the most stable at low/medium temperatures. So does $\ce{Fe2O3}$ converts to $\ce{Fe3O4}$ when heated enough. Note that these oxides as many oxides of transition metals are not fully stoichiometric. $\endgroup$ – Poutnik Jul 23 '20 at 13:07
  • $\begingroup$ @ Poutnik. Thank you for the complementary information. $\endgroup$ – Maurice Jul 23 '20 at 15:52

Per a source : Time-Resolved Mass Spectrometry of Nano-Al and Nano-Al/CuO Thermite under Rapid Heating: A Mechanistic Study, to quote:

The ignition of aluminum particles has been found to be very sensitive to particle size and closely related to the properties of the oxide shell. It has been found that Al-NPs can be ignited at as low as ∼930 K which is close to the melting point of the Al (933 K). The microsized aluminum particles ignite at a much higher temperature of ∼2300 K that is close to the melting point of the oxide shell.7

Here is a comment on the nature of the Al/CuO thermite:

3.2. Nano-Aluminum/CuO Thermite Reaction in TJump/TOMFS. A more vigorous reaction of nano-Al was probed with a thermite mixture using CuO as the oxidizer at a heating rate of ∼5 × 10^5 K/s.

where the use of the adjective 'vigorous' does not reflect, in my opinion, the intensity of the reaction.

However, as noted above, metal particle size is very material, and I would expect primarily molten copper with varying aluminum oxides presence (as cited in the study).


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