USING SOFT-X-RAY ABSORPTION-SPECTROSCOPY TO EXAMINE THE STRUCTURAL-CHANGES TAKING PLACE AROUND SI AND AL ATOMS IN KAOLINITE FOLLOWING FLASH CALCINATION

Structural changes associated with the flash calcination of china clay (Al2O32SiO22H2O) have been investigated using soft X-ray absorption spectroscopy (XANES and EXAFS) at the Al and Si K edges. The data reveal substantial changes to the atomic environment around the Al atomic sites with a reduction of Al-O bond distances from 1.92 angstrom to 1.81 angstrom associated with a change from 6 to 4 coordination. The changes in the structural environment around Si are found to be more subtle with Si remaining tetrahedrally coordinated.