The role of microstrain on the thermostructural behaviour of industrial kaolin deformed by ball milling at low mechanical load

摘要

The high-temperature structural behaviour of kaolin deformed by compaction and shear in a ball mill was investigated by extending the temperature range to 1500 °C. The deformation was induced for the first time with steps of low mechanical load through a specifically built planetary ball milling working in a controlled thermodynamic environment (25 °C and at a vacuum of 0.13 Pa). The investigated kaolin was made of about 65% of a well-ordered kaolinite, 10% of dickite and 25% of quartz. The mechanical energy transfer to the material was measured via the microstrain <ε~2>~(1/2) because we wanted to investigate the details of the evolution of the kaolin modification as a function of the microstrain. At the very early stage of milling (up to 1 h), no strain was accumulated in the kaolinite structure which, however, presented lamination, layer flattening and texturing. Further milling induced a progressive reduction of the stacking layer coherence and an increase of the microstrain, in both cases as a non linear function of the deformation time.