| The conductivity of silver plated on the aluminum oxide, a kind of composite material, was modified by ball milling. The best process was as follows: the weight ratio of Al2O3 to agate ball was 20%, the ball milling frequency was 5.5 Hz, the ball milling time was 3 h. The highest conductivity increased 37 times afer ball milling, reaching 1887 S/cm. The structure and properties were tested by infrared spectrometer, X-ray diffraction, thermogravimetric analyzer, polarizing microscope and suspension. The results showed that ball milling had no effect on the infrared spectrum of alumina, but the infrared absorption peaks belonging to alumina disappeared after silver plating. There were only silver crystal peaks in X-ray diffraction diagram of the composite material. As evidenced by thermogravimetric analysis, the residual of the composite material increased and heat resistance was improved. Polarizing microscope implied that the alumina after ball milling dispalyed a flake structure with uniform size distribution. The composite material could be suspended in ethanol, forming a dark suspension solution, a faverable profile which was expected to improve its dispersion performance in polymer. Finally, the effects of the ball milling on the composite material could be explained by two mechanisms, namely fragmentating large alumina particles and grinding small particles, resulting in the formation of falkes which can increase surface area and silver coating efficiency and improve the conductivity of the material via increasing the connection of conductive network among the particles. The conductive composite material is expected to be useful in many fields such as electromagnetic shielding, conductive adhesive and antibacterial material. |
