Preparation of micro-size flake silver powder by planetary ball mill

Flake silver powder with controllable particle size and specific surface area was prepared using planetary ball mill by varying milling parameters including milling time, revolution speed, and the weight ratio of balls to powder (BRP). As-prepared flake silver powder was characterized by laser particle analyzer, scanning electron microscope, X-ray diffraction (XRD) and thermal gravity analysis (TGA). Results showed that the flake silver powder with the mean size of 4.0 μm and the specific area of 0.64 m² g⁻¹ can be obtained when the revolution speed was 350 r/min, the BRP was 15:1, the grinding time was approximately 30 h and a mixture of 1.5 % stearic acid and 0.5 % oleic acid was used as grinding aids. XRD patterns confirmed that the milled powder was pure silver, indicating there were no silver oxide and the alleged impurities caused by oxidation reaction and friction and wear with the increase of BRP value respectively under the present experimental conditions. TGA showed that the obtained powder was easy to wash and without absorption, which is very important and beneficial to the conductivity of the electrodes.