Measurements of high-temperature viscosities of liquid boron trioxide
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Measurements of High-Temperature Viscosities of Liquid Boron Trioxide N.S. SRINIVASAN, J.M. JUNEJA, and S. SEETHARAMAN HIGH-temperature viscosities of liquid boron trioxide have been measured in the temperature range 1189 to 1610 K, using the rotating cylinder method. Components made from pure iron have been used. The viscometer was calibrated using a standard reference substance for high temperatures. The results obtained are consistent with each other and can be represented by the following relationship:
Temperature (K)
Shartsis e t al. tu
Viscosity (Pa' s) Mackenzie131
Napolitanot41
1075 1175 1275 1375 1475
22.71 11.04 6.01 3.57 2.28
32.93 17.78 10.57 6.78 4.62
35.47 17.74 9.89 6.01 3.90
log~0 (viscosity - Pa. s) = - 5 . 4 8 3 3 + log~0 T + 4 0 7 1 / T Parameters such as bond energy, enthalpy, and entropy of formation of holes in liquid boric oxide have been calculated from the present viscosity data. These are in good agreement with those calculated from literature values. Physical property measurements on simple glass forming systems are helpful in understanding the structural effects in more complex systems such as silicate slags, of relevance to iron and steelmaking. As a part of this study, the present work focuses on the measurement of viscosities of liquid boron trioxide in the temperature range 1189 to 1610 K. Viscosities of liquid boric oxide and other borate melts have been reported in the literature by several workers. Shartsis, et al. t~l used the falling sphere method to determine the viscosities of liquid boric oxide in the temperature interval 725 to 1474 K. Mackenzie t2"3I carried out studies for simultaneously determining viscosity, density, and electrical conductivity of liquid B 2 0 3 in the same apparatus. The data reported are based on the falling sphere method. Napolitano et a l ) 41 used a rotating cup viscometer to measure viscosities over a wide temperature range (591 to 1673 K). Table I summarizes the viscosity data reported by these investigators in the temperature interval 1075 to 1475 K. From Table I, it is seen that there is considerable scatter in the viscosity data available for liquid boric oxide. The disagreement in data has been attributed to the varying water contents in the high-temperature melts used in the various investigations. In these studies, boric acid, as well as pure B203 (99 pct), has been used as a starting material. Prior to viscosity measurement, the melts were dehydrated at 1473 to 1573 K by bubbling dry nitrogen gas. These melts had a water content of less than 0.1 mol pet. According to Napolitano et aL Ia] the relatively low viscosity values reported by Shartsis e t al. ttl are perhaps due to a higher water content in the melt. Mackenzie t31
N.S. SRINIVASAN, Senior Lecturer, and S. SEETHARAMAN, Professor, are with the Division of Theoretical Metallurgy, Department of Metallurgy, Royal Institute of Technology, S-100 44 Stockholm, Sweden. J.M. JUNEJA, Scientific Officer, is with the Metallurgy Division, Bhabha Atomic Research Centre, Trombay, Bombay 4
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