Composition and Structure of NiS Inclusions in Float Glass, and their Impact on the Heat Soak Process

Andreas Kasper, Stephan Moschek, Herbert Stadelmann and Rüdiger Zeihe

The problem brought up here is very complicated. By lack of place it is impossible to go into the real details. The authors apologize for certain simplifications and inaccuracies of the descriptions of phenomena. A more detailed report will be published later in a scientific paper.

NiS inclusions having caused breakage in the Heat Soak Process (HST) or on a building were analyzed by energy dispersive X-ray fluorescence (EDX) in a scanning electron microscope (SEM). Some were found to be homogeneous, solely composed of NiS, and others to contain 2 major phases, the one composed of NiS, the other of Ni9S8. The influence of this difference s on spontaneous failure and comportment in HS process is actually unknown.

Different iron (Fe) concentrations were also found in the NiS bulk, evidently correlated with the glasses' iron content, and ranging from very low values (<0.2 at.-% in clear glass) up to 2 at.-% in green glass. In the gussets and pores between the NiS bulk crystals, sulfide crystals containing up to 48% iron were found.

The corresponding bulk nickel sulfides were produced synthetically, and their kinetic properties measured by differential scanning calorimetry (DSC). An important difference in activation energy was found between iron-free and iron-containing species. With increasing number of DSC loops, the difference between the substances vanishes more or less.

We think that we have found one of the parameters causing a difference in breakage behavior between toughened glass on façades, and the same in HS process.

Full-Text Article [216 KB]

The Authors

Dr. Andreas Kasper Dr. Saint-Gobain Profession: ChemistOccupation: Head of project group "chemistry of glass melting"Responsibilities:Chemical analysis of glass and raw materials; environmental measurements (emissions of glass tanks); s... Read more