Compositional effect on fining and oxygen activity in mixed alkali silicate glasses

• This study monitors, in situ, how alterations of the glass composition affect the results of fining and the oxygen activity (aO2) of the melt. The number of bubbles in annealed glass samples was determined in order to evaluate the fining efficiency. Electrochemical measurement of aO2 was used to monitor in situ the fining charcteristics and conditions of Na2O-K2O-CaO-SiO2 glasses. The glasses investigated had a constant alkali oxide content, but a varying ratio of Na2O/(Na2O+K2O). The Sb2O3 content was o.2 mole-% and NaNO3 or KNO3 was added as oxidising agent in most of the glasses. The results show that the number of bubbles decreases from approximately 1100 to 200 bubbles/ 100 g glass and that aO2 at 1400 deg C increases from 0.2 to 1.2 bar in the glass melt when increasing the Na2O/(Na2O+K2O) ratio from 0 to 1.

Nyckelord

glass. oxygen activity

fining

Technology (byts ev till Engineering)

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