UV/VIS‐spectroscopy of liquid slags

Abstract

UV/VIS‐spectroscopical methods have been applied to investigate the absorption behaviour of CaO‐Al2O3‐SiO2‐slags in a wide temperature range from 20 to 1655°C. The observations reveal a strong temperature dependence of the absorption bands, which can be explained by means of a newly developed theoretical model. The model also correlates the observed long‐frequency UV cutoff‐wavelength with the optical basicity. The definition of the optical basicity has been corrected for higher temperatures, since there are remarkable deviations between the solid and the liquid state, which have not been taken in consideration yet. Further investigations on a CaO‐Al2O3‐slag containing CaF2 at 1500°C show that no Fe3+… F‐complexes like Fe3+(F−)4 or Fe3+(F−)6 are formed. F− reacts with Al3+ forming Al‐O‐F‐complexes. The F−‐ions displace the O2‐‐ions from the Al3+. This causes the basicity to increase.

Application of UV/VIS‐Reflection Spectroscopy for Determination of the Oxidation State of Liquid Slags with High Fe3+‐Contents

“…The behaviour of the 3d-cation s varies strongly. In glassy silicates, C0 2+ appears in form of a tetrahedral complex C0 2 +(02')4 at room temperature [9]. With increasing temperature , the complex dissociates and the originally deeply blue coloured silicates become more and more transparent:…”

“…The dissociation degree jJ of the complex in a silicate 54.5CaO+45.5Si0 2 (mass-%), doped with 1.5 % CoO , amounts tojJ=O.9 (1450 "C) according to equation (1) (see [9]). In the glassy silicate of the mineral haplogranitic , Ni 2 + (doping between 0.13 and 1.3 mass-% NiO) exists as an octahedral comple x Ni z +(02')6 that dissociates to the tetrahedral complex Ni 2 +(Oz-)4 with decreasing temperature (approximately 86 % Ni 2+ (02')4 at 1300°C, liquid state) [17].…”

“…78 (2007) NO. 9 sicity is derived from this principle. It has not yet been possible to establish completely and sufficiently exactly the relation between the optical basicity and the content of oxide ions as electron donors in different glassy solidified borates, phosphates and silicates.…”

“…In glasses, the coordination number at room temperature is an important parameter for a description of the chemical bond whereas, in liquid systems, thermal dissociation equilibria of coordinative bonds (complexes) dominate. Due to the strong thermal fluctuations, the bond distances become fuzzy and the measurements provide only average coordination numbers [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. These results are based on the application of methods from optical spectroscopy [7][8][9][10]17], X-ray and neutron diffraction [11][12][13][14][15][16]20] and NMR and XAFS-spectroscopy [19,21] on liquid silicates, borates and aluminates.…”

Ultraviolet/visible reflection spectroscopy of molten and glassy silicates (MeOn–CaO–SiO2) and phosphates (MeOn–CaO–P2O5), Men+=Fe3+, Mn2+

“…The s-p-transition (nephelauxetic effect) of main group cations Pb 2+ , Bi 3+ or Tl + in glasses can be measured by means of optical-spectroscopy at room temperature and is located in the UV range. We have not found a quantitative correlation between the redshift of the s-p-transition and the PaulingÕs electronegativity quantitatively by such investigations [8,35,43]. The concept of the optical basicity is derived from this principle.…”