V4+ in quenched calcium silicates: An electron spin resonance spectroscopic investigation
2003
Farah, H.
Electron spin resonance (ESR) studies of vanadium(IV) have been carried out on CaO-SiO₂, CaO-MgO-SiO₂ and CaO-Al₂O₃-SiO₂ slags equilibrated with oxygen partial pressures over the range 10⁻⁹–10⁻² atm and also CaO-SiO₂-V₂O₅-Fe₂O₃ slag melted in air. The slags were melted at 1873 K and their V₂O₅ level was varied between 1 and 10 mol%. Three different melt basicities and alumina contents were investigated. Magnesia content was varied between 3.5 and 4.9 wt%. An industrial slag sample was also examined. The spin Hamiltonian parameters were determined and it was concluded that the paramagnetic vanadium was in the form of a distorted octahedral vanadyl complex (VO²⁺). An overlapping signal from a yet unknown paramagnetic vanadium species was present in all slags. In general this signal diminished with reduction in the oxygen pressures below 10⁻⁶ atm and V₂O₅ content. It also decreased with increase in basicity and magnesia content. The critical fraction of paramagnetic vanadium for induction of the second species was dependent on melt composition.
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