Dissolution of water vapour in ESR-slags of the systems CaO-Al2O3and CaF2-CaO-Al2O3by application of Fourier-Transform-Infrared-Spectroscopy

In CaO–Al2O3- and CaF2–CaO–Al2O3-slags the soluted water vapour was quantitatively determined with Fourier-Transform-lnfrared-(FT-IR-)spectroscopy. The slags were equilibrated at 1500 and 1600 °C with definite H2O- and H2O/HF-partial pressures, respectively. The liquid slags were quenched in liquid D2O. They solidified glassily. Water vapour exists in the slags soluted as OH−-ion. For all slags investigated a linear dependence of the integral extinction upon the square root of the H2O-partial pressure, respectively upon HF-partial pressure, was determined. The values of the integral extinction (CaF2–CaO–Al2O3-slags) are calibrated by a H2O-doping-technique. The solution enthalpy of H2O in CaO–Al2O3-slags was estimated: endothermal reactions. Interpretation of the vibrational range yielded in a mainly tetrahedral coordination of Al3+ with O2−- and F− -ions in the glassy state. By heating the glassily solidified CaO–Al2O3-slags were transformed into their crystalline products: shifting of IR-peaks. The CaO–Al2O3- and CaF2–CaO-slags were compared with a CaO–SiO2–Al2O3-slag. The FT-IR-method is quick. The water content can be estimated with an uncertainty of less than ± 5% and is, therefore, suitable for process control of metallurgical procedures.