Ceramics-Silikáty 46 (1) 1-7 (2002)

STRUCTURAL AND MECHANICAL RESPONSE TO A THERMO-RHEOLOGIC HISTORY OF SPINEL SLUDGE IN HIGH-LEVEL WASTE GLASS

 M. Jiřička, P. Hrma

The composition and structure of a sludge sample from a high-level waste glass melter were studied using optical and scanning electron microscopy, and x-ray diffraction. At isothermal heat treatments between 1050°C and 1350°C, spinel crystals partly dissolved to form on cooling tiny (~ 10 mm) star-like crystals or dendrites. The shear stress in sludge was measured at a constant shear rate (from 0.005 s^-1 to 1.0 s^-1) and temperature (from 1050°C to 1350°C) during repeated deformation and after idling. The initial thixotropic character of the loose structure of the settled sludge turned on subsequent deformation (and idling) to rheopectic behavior. As the spinel concentration in the sludge decreased from 28 mass% (sludge as received) to 15 mass% at 1300°C, the sludge turned into a Newtonian suspension.

Keywords: Glass, Spinel, Rheology