Abstract
Oxygen transfer rates, P, through molten NiO-CaO-SiO2, ZnO-CaO-SiO2 and NiO-ZnO-CaO-SiO2 systems were measured by using a molten thin film penetration method developed by the author. Temperatures of the measurement were about 1 450, 1 500 and 1 550°C.
The transfer rates were 1 to 5 time 10-8 mol·O2·cm-1·s-1. They were the same order of the magnitude as that in the case of iron oxide-CaO-SiO2 system measured previously. In the case of system containing NiO, the more NiO contents the higher oxygen transfer rate. On the other hand, in the case of system containing ZnO, the higher ZnO contents the higher oxygen transfer rate in the case of less than 20mol%ZnO and the higher ZnO contents the lower oxygen transfer rate in the case of more than 20%ZnO.
Effects of constituent on oxygen transfer rate, P, with the unit of mol O2·cm-1·s-1 are empirically expressed as follows:
System less than 12.5 mol% NiO : P = 3.15×10-9 (mol%NiO)
System less than 35mol% ZnO : P = -8.5×10-11 (mol%ZnO-22)2+4.2×10-8
Temperature dependencies of the oxygen transfer rates are as follows:
7.5 mol%NiO-46.3 mol%CaO-46.3 mol%SiO2 : P = 3.51×10-2 exp (-25.3×103 / T)
10 mol%ZnO-45 mol%CaO-45 mol%SiO2 : P = 3.24×10-2 exp (-25.3×103 / T)
20 mol%ZnO-40 mol%CaO-40 mol%SiO2 : P = 6.39×10-2 exp (-25.3×103/ T)
30 mol%ZnO-35 mol%CaO-35 mol%SiO2 : P = 4.96×10-2 exp (-25.3×103 / T)
It was estimated that NiO and ZnO acted as p- and n-type semiconductors, respectively, on the basis of the discussion on the dependency of the transfer rate on oxygen partial pressure at the surface of the molten oxide.
