Characterization of the microstructure of mechanically-activated olivine using X-ray diffraction pattern analysis

• Mechanical activation results in great structural changes in olivine crystal.
• The amorphization degree increased to 40% after 120 min mechanical activation.
• The lattice volume of olivine compressed first and then expanded.
• Crystallite size decreased and microstrain increased during mechanical activation.
• Rietveld method was the most suitable method for characterizing the microstructure of olivine.

During mechanical activation, disorder in the crystal structure of olivine has been recognized as one of the most important factors for enhancing the reaction rate of downstream carbonation processes. This paper investigates the detailed microstructure of olivine after mechanical activation in a SPEX 8000 mill using the X-ray diffraction technique. In order to successfully extract information from the microstructure using X-ray diffraction patterns, various models were applied and compared, including the Scherrer method, Williamson–Hall method, Multiple Whole Profile fitting method, and Rietveld method. Results show that with 120 min of milling, the media particle size initially decreased dramatically, and then increased slightly, the BET surface area and amorphization degree increased, the lattice was initially compressed and then expended, the crystallite sizes decreased, and strains increased. The strain value for 120-min mechanically-activated olivine, calculated by the Scherrer method, Williamson–Hall method, Rietveld method, and MWP method, was 2.15 × 10−3, 1.64 × 10−3, 0.73 × 10−3, and 0.28 × 10−3, respectively. The Rietveld method was found to be the most accurate method and therefore most suitable method for characterizing the microstructure of olivine and mine waste materials containing olivine.