Using manganese dioxide as a ferric oxide replacement? Looking back at results.

Manganese dioxide. Mn is closest neighbour to iron, molecular weight is one less than that of iron. 54.938g/mol. Win for manganese.

1. MnO2 has more oxide content than Fe2O3, as 2:4 is better than 2:3. Win for burel (MnO2).
2. Standard enthalpy of formation for MnO2 is −520.9 kJ/mol, while for Fe2O3 it is −825.50 kJ/mol. MnO2 has more energetic potential per oxygen and per molecule. Double win for MnO2.
3. Fe2O3 decomposes only at its melting point of 1566 °C (1838 K). MnO2 releases first oxygen at 535 °C (or 553°C for 95% purity paint grade) and this process continues up to 800°C. 2*MnO2 -> Mn2O3 + O2. Mn2O3 melts at only 940°C. By heating Mn2O3 or MnO2 over 800°C~1000°C further oxygen is being released when Mn2O3 molecules transform into Mn2O3.MnO complex. Mn2O3.MnO is very catalytically active, reducing nitrogen oxides and oxidizing CO, both reactions we need for more heat in combustion. Total combustion of light organics has been observed at only 400°C on Mn2O3.MnO! Quardruple win for Mn2O3+Mn2O3.MnO!
   
4. Fe2O3 melts at 1566 °, and Mn2O3.MnO melts at 1590°C. While we typically have much higher surface area in the Fe2O3, the Mn2O3.MnO has been already in liquid form at lower temperatures and released one third of the oxygen by that time and now all hell will break loose with this strong catalyst as it gets liquid! A win for Mn2O3.MnO I guess.

Some of the sources:
Iron (III) oxide
Manganese dioxide
Manganese (III) oxide
Manganese (II,III) oxide
Problems? Yes.

1. You will not get MnO2 in the same superfine powder as you can get the ferric oxide. The MnO2 particles will be about double the size and I think the ultrafine dust will not be present between them. A big lose point for MnO2.
2. The same variety of manganese compounds has higher stability than its iron counterparts. KMnO4 for example exists in solid state, KFeO4 exists only in certain solutions and decays quickly. Iron compounds are easier to decompose.
3. For superior performance of MnO2 you need very high combustion temperatures, or at least localized burn points of over 1600°C. This can be helped by introducing magnesium powder into the mix. Most rockets can't affort that complication.
4. Fe2O3 and iron compounds react with saccharose and glucose to form saccharates and gluconates.
5. Fe2O3 dissolves in molten KNO3.

In the large comparative test Richard Nakka made here you will see that the surface area of the CuO and MnO2 was far, far inferior to the "brown iron oxide" which is perharps just the finest milled alpha-Fe2O3 that is sold, red iron oxide, that is so finely milled that it appears as dark brown.

One other explanation yet to be proved is that the brown pigment was fine mix of either Fe2O3.FeO+Fe2O3 like pigments SHD or the Fe2O3 + MnO2 pigment HM.

Links:
Color chart of the concrete pigment types
Table of composition of various pigments.

Also note that I still insist on existing chemical reaction between sugar and the superfine TD-202 pigment I use. Burn rate of 4.79mm/s on air.