Effect of cycled combustion ageing on a cordierite burner plate

A combination of 57Fe-Mossbauer spectroscopy and X-ray Powder Diffraction analysis has been employed to study modifications in chemical and mechanical stability occurring in a cordierite burner aged under combustion conditions which simulate the working of domestic boilers. Mossbauer study shows that Fe is distributed into the structural sites of the cordierite lattice as Fe2+ and Fe3+ ions located mostly at octahedral sites. Ferric oxide impurities, mainly hematite, are also present in the starting cordierite material accounting for ≅40% of the total iron phases. From Mossbauer and X-ray diffraction data it can be deduced that, under the combustion conditions used, new crystalline phases were formed, some of the substitutional Fe3+ ions existing in the cordierite lattice were reduced to Fe2+, and ferric oxides underwent a sintering process which results in hematite with higher particle size. All these findings were detected in the burner zone located in the proximity of the flame and were related to possible chemical reactions which might explain the observed deterioration of the burner material.