Structural analysis of slag using multinuclear solid state NMR

A new approach to structural analysis of the slag has been proposed using multinuclear solid state NMR that is capable of obtaining the structural information of each element composing the slag such as Si and Al, and effective to both crystalline and non-crystalline solid materials. In this study, we applied F-19 (I = 1/2), Si-29 (I = 1/2) and Al-27 (I = 5/2) solid state NMR to two types of steel-making slags, that differ in Al contents; 2.94 mass% (slag A) and 0.10 mass% (slag B). Measurement of F-19 magic-angle-spinning (MAS) NMR enables to determine which metal among Ca, Si and Al is directly bonded to F. In these slags, F was found to be mainly coordinated by Ca. The state of SiO4 network (Q(n)) was estimated by Si-29 MAS spectra. As the result, it was found that highly condensed network of SiO4 tetrahedron such as Q(2), Q(3) and Q(4) does not exist in these slag systems. In Al-27 NMR measurement, two-dimensional Al-27 multiple-quantum magic-angle-spinning (MQMAS) NMR was applied which can average the second-order quadrupolar interaction. Drastic improvement of spectral resolution at high field (16.4 T) 5QMAS experiment clarified the existence of at least 11 chemical sites of Al in slag A. From the above mentioned results, multinuclear solid state NMR is proved to be a very effective method in characterization of the slag.