Low expansive glass-ceramic material produced from blast furnace slag and china clay


ISSN 1121-7588
S. Mandal, S. Chakrabarti, S. Ghatak, S.K. Das
Clay & Traditional Ceramics Division, Central Glass & Ceramic Research Institute, P.O. Jadavpur University, Kolkata, India

Abstract

A glass composition based on the Li2O-Al2O3-SiO2 (LAS) ternary diagram was prepared utilizing blast furnace slag (a by-product from steel plant) and china clay. The batch was modified by the addition of lithium carbonate, hydrated alumina, boric acid and titania (TiO2).Titania was used as a nucleating agent. The batch was melted at 1400 oC followed by casting in the form of bars and annealed at 510 oC for 4h.The annealed specimens were subjected to heat treatment at predetermined temperatures, selected from DTA study of the parent glass.The specimen nucleated at 520 oC for 1 h and crystallised at 620 oC for 2h resulted a very low coefficient of thermal expansion [0.064 to 10.19X10-7/ oC] in the temperature range of 30 to 500 oC due to the formation of b-eucryptite, g-eucryptite and LiAlSi3O8 crystalline phases, while other heating schedules showed the formation of spodumene and associated lithium aluminium silicate phases. All the samples showed excellent flexural strength value and varied in the range of 118-200 MPa. The micro-structural features were also examined through SEM study. Formation of dense microstructure was noticed in the sample nucleated at 520 oC for 4 h and crystallized at 620 oC for 2 h.
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