PLASTICITY-IMPARTING CAPACITY OF RADIATION DAMAGED HIGH-HINCKLEY INDEX KAOLINITE

Abstract

Irradiating kaolinite crystals with electron beams is known to cause radiation damage and result in amorphization. For this study, we irradiated radiation to kaolinite with a high Hinckley index and investigated the increase in plasticity-imparting capacity. For the first experiment, samples of two types were prepared: a dried coarse sample with a Hinckley index of 1.41 and a 7.66 µm median particle diameter. The slip sample made by adding water to the same sample. These samples were irradiated with ⁶⁰Co-γ rays at two levels: 50 kGy and 100 kGy. The hygroscopicity rate was investigated as an indicator of plasticity-imparting capacity, the peak-to-background ratio and crystallinity in X-ray diffraction as indicators of amorphization, and the Hinckley index and S-Hinckley index as indicators of stacking fault. The results suggest that radiation damage caused amorphization and a decrease in plasticity-imparting capacity. The slip sample irradiated with ⁶⁰Co-γ rays at 100 kGy showed a diffraction peak at 1.43 nm, which subsequently disappeared. For the next experiment, we used a fine-grained sample obtained by wet grinding the above kaolin in a ball mill. The Hinckley index of the fine-grained sample was 1.05. The median particle diameter was 4.25 µm. In this experiment, the slip samples were irradiated with ⁶⁰Co-γ rays at a dose of 100 kGy. The hygroscopicity rates were 0.95% for the non-irradiated sample and 0.87% for the irradiated sample. The peak-to-background ratio changed from 45.40 for the non-irradiated sample to 42.35 for the irradiated sample. Through two experiments, amorphization caused by radiation exposure differs from the amorphization of secondary clay, suggesting reduction in its plasticity-imparting capacity.