(197f) Investigation of the Oxidation Behavior of Copper/Tin and Copper/Carbon Composite Particles Fabricated Via Spray Pyrolysis

Copper particles have potential applications in conductive pastes for printed electronics, metallization of solar cells, and interference packaging. However, copper powders are easily oxidized even at room temperature under ambient air. Therefore, numerous efforts have been made to increase the oxidation resistance of copper powders by addition of a secondary component. Among them, copper/tin and copper/carbon composite particles seem promising, considering the price of the raw materials and the resistivity of the particles. However, the oxidation behaviors of copper/tin and copper/carbon composite powders need to be investigated first.

Up till now, the investigations of copper-based composite particles have been restricted to a small range of secondary components, such as silver. As silver does not react with oxygen, the oxidation processes of these composite particles are simplified. For other composite particles whose secondary components can also be oxidized, research is needed to understand the underlying oxidation mechanism of the composite particles as a whole as well as the oxidations of each individual component.

Here, the oxidation behaviors of copper/tin and copper/carbon composite particles are reported. Spray pyrolysis was utilized to fabricate the dense and solid copper/tin and copper/carbon composite particles. X-ray powder diffraction (XRD) was performed to understand the evolution of the crystal structure in the particles. The Rietveld refinement results showed that with the increase of tin concentration in the composite particles, the relative amount of Cu₂O decreased from 60 wt % for Cu0.95Sn0.05 to 10 wt % for Cu0.9Sn0.1 after the samples had been heated for 10 min at 300 ^oC under ambient air. In addition, CuO was only found in the pure copper sample after heating for 10 min at 300 ^oC also under ambient air. All the results showed that pure copper samples were severely oxidized compared to the composite particles. To further explore the oxidation processes, in-situ XRD was conducted to detect crystal transformations in the composite particles during oxidation. When the samples were continuously heated under ambient air with a ramp of 5 ^oC/min, oxide peaks were found in the pure copper powders when the temperature was below 300 ^oC. For the composite particles, oxide peaks began to appear in the XRD patterns when the temperatures were higher than 300 ^oC. Our preliminary results show that adding a second component such as tin can improve oxidation resistance. Results for carbon as the second component will also be presented.