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The present study investigates the wetting and corrosion behaviour of slags on dense Al2O3 ceramics, focusing on the influence of varying vanadium- and titanium oxide content. Physicochemical properties of the slag were assessed by measuring wetting angles, heights and diameters of the molten slags on the alumina at different temperatures. Microscopic observations and elemental composition analysis were conducted on the interface between the corroded Al2O3 ceramics and the slags. Our findings demonstrated that the V2O3 addition in the slag leads to its oxidation to V2O5, which further reacts with Fe2O3 and MnO to form low melting point phases such as FeVO4 and MnVO6. Consequently, the melting point of the slag decreases significantly, resulting in a decreased wetting angle with the Al2O3 ceramics. The presence of unsaturated alumina in the slag leads to the dissolution of aluminium ions from the ceramics into the slag, which reacts with Fe2O3 and MnO to form spinel phases, contributing to material loss of the ceramics. Infiltration of the slag into the Al2O3 predominantly occurs through the alumina grain boundaries. Two types of infiltration are identified: one involving reactions with alumina to form low melting point phases like Fe2O3 and the other involving inherent low melting point phases such as MnVO6. In contrast, the penetration of SiO2 into the alumina substrate is limited. Additionally, the dissolution of Al2O3 into the slag creates pathways for further infiltration. This study highlights the significant influence of Ti and V content on the physicochemical properties of the slag and provides insight into the corrosion mechanism of Al2O3 ceramics by Ti and V containing slags.

Raman spectroscopy and Electron Paramagnetic Resonance (EPR) studies were performed on a series of V2O5/TiO2 catalysts prepared by a modified sol-gel method in order to identify the vanadium species. Two species of surface vanadium were identified by Raman measurements, monomeric vanadyls and polymeric vanadates. Monomeric vanadyls are characterized by a narrow Raman band at 1030 cm−1 and polymeric vanadates by two broad bands in the region from 900 to 960 cm−1 and 770 to 850 cm−1. The Raman spectra do not exhibit characteristic peaks of crystalline V2O5. These results are in agreement with those of X-ray Diffractometry (XRD) and Fourier Transform Infrared (FT-IR) previously reported (C.B. Rodella et al., J. Sol-Gel Sci. Techn., submitted). At least three families of V4+ ions were identified by EPR investigations. The analysis of the EPR spectra suggests that isolated V4+ ions are located in sites with octahedral symmetry substituting for Ti4+ ions in the rutile structure. Magnetically interacting V4+ ions are also present as pairs or clusters giving rise to a broad and structureless EPR line. At higher concentration of V2O5, a partial oxidation of V4+ to V5+ is apparent from the EPR results. [ABSTRACT FROM AUTHOR]