Experimental procedures Milling experiments
Milling experiments: Milling experiments were performed using a planetary mill (PM-D0.4L, Droide Instrument & Equipment (Shanghai) Co., Ltd., China) with an air cycle refrigeration system under different temperatures. Four agate ball milling jars, with a volume of 50 cm3 and contain 10 balls ( = 10 mm) of the same material, were used.