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

Abstract

In CaO-AI 203-and CaF2-CaO-AI,03-slags the soluted water vapour was quantitatively determined with Fourier-Transform-Infrared-(FT-IR-)spectroscopy. The slags were equilibrated at 1500 and 1600°C with definite H 20-and H 20/HF-partial pressures, respectively. The liquid slags were quenched in liquid 0 20. 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 H 20-partial pressure, respectively upon HF-partial pressure, was determined. The values of the integral extinction (CaF 2-CaO-AI203-slags) are calibrated by a H 20-doping-technique. The solution enthalpy of H 20 in CaO-AI 203-slags was estimated: endothermal reactions. Interpretation of the vibrational range yielded in a mainly tetrahedral coordination of A13+ with 0 2-and F--ions in the glassy state. By heating the glassily solidified CaO-AI 203-slags were transformed into their crystalline products: shifting of IR-peaks. The CaO-AI 203-and CaF.-CaO-slags were compared with a CaO-Si0 2-AI203-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. Wasserdampfloslichkeit in geschmolzenen ESU-Schlacken der SystemeCaO-AI.0 3 und CaF.-CaO-AI.0 3 unter Anwendung der Fourier-Transform-Infrarot-Spektroskopie. In CaD-AI 203-und CaF 2-CaO-AI203-Schlacken wurde geloster Wasserdampf mit der Fourier-Transform-Infrarot-(FT-IR-)Spektroskopie quantitativ bestimmt. Die Schlacken wurden bei 1500 und 1600°C mit definierten H 20-bzw. H 20/HF-PartialdrOcken ins Gleichgewicht gesetzt. Die f10ssigen Schlacken wurden in schwerem Wasser abgeschreckt. Sie erstarrten glasig. Der Wasserdampf lost sich in den Schlacken als OH--Ion auf. FOr aile untersuchten Schlacken wurde lineare Abhanqiqkeit zwischen integraler Extinktion und der Quadratwurzel des H 20-Partialdruckes bzw. HF-Partialdruckes bestimmt. Die integrale Extinktion (CaF 2-CaO-AI203-Schlacken) wurde durch eine H,o-Dotierungstechnik geeicht. Die Losunqsenthalple des Wassers in CaO-AI 203-Schlacken wurde bestimmt: endotherme Reaktionen. Die Auswertung des Schwingungsbereiches der Schlackenkomponenten ergab, daB AI'+ bevorzugt mit 0 2-bzw. F--Ionen tetraedrisch koordiniert ist. Umkristallisation der glasig erstarrten CaO-AI 203-Schlacken wurde durch Tempern erreicht: Verschiebung von IR-Peaks. Die CaO-AI,03-und CaF 2-CaO-AI203-Schlacken wurden mit einer CaO-Si0 2-AI203-Schlacke verglichen. Die FT-IR-Methode ist schnell. Der Wassergehalt kann mit einem Fehler unter ± 5 % bestimmt werden. Sie ist deshalb zur ProzeBkontrolle bei metallurgischen Ablauten geeignet.

FT-IR Spectroscopic Study on Structure of CaO-SiO2 and CaO-SiO2-CaF2 Slags.

“…This distortion will weaken the remaining Si-O bonds in [SiO 4 ]-tetrahedra, decreasing the force constants and the frequencies of vibrations involving Si-O bonds. 21,35,36) In Fig. 4, it is shown that the center of gravity of the bands at about 1170-710 cm Ϫ1 slightly shifts from about 980 to 850 cm Ϫ1 by increasing the ratio F/S from 0.22 to 0.64.…”

Structural Investigation of CaO-Al2O3 and CaO-Al2O3-CaF2 Slags via Fourier Transform Infrared Spectra.

“…There are four kinds of band groups at about 940-720, 720-600, 580 and 470 cm Ϫ1 ; these groups, respectively, correspond to the asymmetric stretching vibration of the [AlO n F 4Ϫn ] (nϭ0-4) tetrahedral complexes, [AlO 4 ]-tetrahedra, [AlO 6 ]-octahedra, and [AlF 6 ]-octahedra. [5][6][7][8][9][14][15][16][17] The assignment of band groups at about 940-720 cm Ϫ1 to the [AlO n F 4Ϫn ]-complexes is based on an increased asymmetry of vibration due to coexistence of Al-F and Al-O bonds in these complexes. (4) Equation (4) indicates that the product of activities of aluminate tetrahedra and F Ϫ ions could be a driving force for the depolymerization of aluminate network by F Ϫ ions under the condition of a CaO ϭ1.…”

“…7) On the other hand, Leekes et al suggested that the asymmetric stretching vibration of the [AlO 4 ]-tetrahedra could be identified as an absorption band at 850-790 cm Ϫ1 from FT-IR spectra of the (fluoro-) calcium aluminate slags. 8) In the CaO-Al 2 O 3 -CaF 2 slag, the range of the F-Al-O vibrations was nearly identical with that of Al-O vibrations; thus, Al 3ϩ ions were considered to be tetrahedrally coordinated with oxygen and fluorine ions. They also discussed the relationship between CN and Al-O bond length on the basis of Badger's rule defined by Eq.…”

“…8,9) However, the relative intensity of [AlO 6 ]-octahedra continuously increases with increasing CaO content, indicating that the oxygen ions dissociated from CaO would react with [AlO 4 ]-tetrahedra to produce [AlO 6 ]-octahedra, based on Eq. (3).…”

Enhancement of Rutile Formation by ZrO₂ Addition in Ti-bearing Blast Furnace Slags

“…As shown in Fig. 5, the FTIR spectrum consists of a strong broad band in the wavenumber range of about 1 200 to 800 cm -1 , a medium intense band between about 600 and 480 cm -1 and a weak band [25][26][27][28][29][30][31][32] and the adsorption bands of different structural units are showed in Table 2. The strong wide band generally consists of four peaks at about 860, 920, 960 and 1 080 cm -1 , corresponding to the stretching vibration of [SiO 4 ]-tetrahedra with various NBO/Si(4,3,2,1), [25][26][27][28][29][30] namely Q 0 , Q 1 , Q 2 and Q 3 .…”