Development of a New Viscometer Based on Rotating Crucible Method and Viscosity Measurement of SiO2^|^ndash;CaO^|^ndash;CaF2 System

Abstract

The development of a new viscometer based on rotating crucible method and the viscosity measurement of SiO2-CaO-CaF2 system were carried out. The viscometer was hermetically closed, and the atmosphere around the melts was highly controllable. In the viscosity measurement, an inner cylinder made of graphite was immersed into the melts in a graphite crucible under Ar at elevated temperatures (1 467-1 782 K). The torque given to the inner cylinder by rotating the crucible was measured by means of a supersensitive torque sensor, and the viscosity was determined. The minimum limit of the viscosity determined was 20 mPa•s. A special attention was paid to keep the temperature uniformity inside the furnace for precise measurement by placing tungsten plates as the thermal shield, and the excellent temperature uniformity (±0.2 K in a whole crucible) was obtained. The basicity (= CCaO/CSiO 2 in mass) of the melts was 0.79 or 1.25, and the concentrations of CaF2 were 5, 10, 15, 20, 25 mass%. As the results, the viscosity of the melts showed a good Arrhenian type linearity in any samples. The loss of fluoride from the melts after the measurement was very small which suggests the consistency of melt composition. The viscosity of the melt decreased with increasing the concentration of CaF2, but the degree of decrease was smaller than literature values. The decrease in the viscosity of the melts with the addition of CaF2 in acid region is slightly greater than that in basic region.

Effect of CaF2 Addition on the Viscosity and Structure of CaO–SiO2–MnO Slags

“…In order to meet these requirements, it is necessary to consider and quantify the effect of fluorspar (CaF 2 ) addition on the viscosity of MnO-containing slags at high temperatures, because the CaF 2 is well known to decrease the viscosity of silicate melts. [3][4][5][6][7][8][9][10][11][12]15,19,20,24) The experimental study of the effect of CaF 2 on the viscosity of various silicate melts has been investigated by several researchers for CaO-SiO 2 (-MgO)-CaF 2 , [3][4][5][10][11][12]24) FeO(-CaO)-SiO 2 -CaF 2 , [6][7][8] CaOSiO 2 -Na 2 O-Li 2 O-CaF 2 , 19) and CaO-Al 2 O 3 -SiO 2 -MgO-CaF 2 systems. 20) From the above studies, the viscosity itself and the activation energy of Newtonian flow of silicate melts generally decrease with increasing content of CaF 2 due to depolymerization reactions of silicate networks, indicating that the addition of CaF 2 is more effective in higher silica content region.…”

Viscosity Measurement of Slags using Rotating Bob and Vibrating Finger Viscometer

“…[8][9][10][11][12][13][14][15][16] However, it is difficult to determine a precise low torque due to the mechanical friction inside the viscometer. 17) Viscometers of this type consist of two concentric cylinders (a bob and a crucible) and the viscosity is determined from the calculations of the torque of bob at constant or different rotations. A few other studies were reported to use the different types of viscometers such as the rotation crucible viscometer and the oscillating plate method.…”

“…A few other studies were reported to use the different types of viscometers such as the rotation crucible viscometer and the oscillating plate method. [17][18][19][20] The concentric cylinder method was primary used for the determination of slag viscosity. It…”

Effect of Additives (Alumina, Magnesia or Calcium Fluoride) on Dissolution Rate of Solid CaO into Calcium Silicate Based Slags

“…$ η values mean the viscosity of the slags at 1823 K. For the CaO-SiO2-Al2O3 and the CaO-SiO2-MgO system, the temperature dependences of the viscosity, which were reported by the group of Machin et al [23][24][25] , are extrapolated and listed in this Table. (Viscosity data of the 30 mass%CaO-60 mass%SiO2-10 mass%Al2O3 (or MgO) are used instead of those of the 32 mass%CaO-58 mass%SiO2-10 mass%Al2O3 (or MgO) slags in this Table.) The viscosities of the CaO-SiO2-CaF2 system were determined by interpolation of the data reported by Takeda et al 26) . * Density of the bulk slag, ρb, was calculated based on the additivity rule using the reported partial molar volume values determined at 1773 K 27) .…”