Combined SEM-EDX and μ-Raman spectroscopy for the characterisation of glass/Al-rich refractory interfaces

Abstract.

Crystalline inclusions, commonly called stones, are very dangerous defects present in industrial glass products. Refractory materials of the furnace, raw materials and ceramic grains introduced with glass cullet, are the main sources of stones. To improve the quality of glass products, the understanding of the mechanisms responsible for the formation and the transformation of these defects is required. At the interface glass melt/stone surface several reactions occur leading to the formation of new glassy and crystalline micro-phases. These phases are usually studied by scanning electron microscopy and X-ray microanalysis on polished cross sections. Nevertheless SEM-EDX chemical analysis alone does not allow the complete identification of the different phases.

In this work, the reactions occurring between refractory materials and the molten glass were studied with a micro-chemical and micro-textural approach completed by micro-structural investigation. Compositional and textural features were investigated by SEM-EDX and by μ-Raman spectroscopy. Raman spectra of pure crystalline well identified compounds were compared with those of the unknown phases. This technique allowed to identify the nature of the re-crystallized phases. The combined use of SEM-EDX and μ-Raman techniques revealed to be very promising in the study of the origin and in the characterization of stones in glass.