Research On Process Of Reduction Of CuO With Atmospheric Pressure Plasma

The reduction method with atmospheric pressure plasma jet is widely used in surface processing of polymer, metal, semiconductor and PCB because of its outstanding advantages, such as clean, efficiency, simple equipment and little influence in material performance. This technology can solve the remove problem of copper oxidation when it used for PCB. And it is also both efficient and environment friendly when instead of activating treatment in plating process. In addition, the technology can also be used to connect the ceramic and metal. However the gas medium used for reduction process is usually hydrogen, which has many security risks in the transport, storage and use. Furthermore there are few studies for the mechanism of plasma reduction currently. So in this article a new plasma gas instead of hydrogen was searched. The influence of gas medium and technological parameter on microstructure, phase composition and distribution of element in the reduction of CuO with atmospheric pressure plasma were evaluated by SEM, XRD and EDS analysis. The effect of the parameters has been discussed, and the reduction craft has also been optimized. The mechanism of plasma reduction has been analyzed through the detection results, which could provide theoretical guidance and technical support for other applications of technology of plasma reduction.In this experiment, N₂, N₂⁺NH₃ and N₂⁺decomposed NH₃ were used as plasma gas respectively. The results indicated that the order of reducibility of three gas mediums was N₂⁺decomposed NH₃ > N₂+NH3 > N₂ through combining the production principle of plasma, the active species in three gas mediums and the phase composition.The reduction time of plasma had an important influence on reduction of CuO: the relative content of reduction products of Cu was increased first and then decreased in the case that reduction time prolonging, and its content reached the highest which was 34.38% when reduction time was 70s; The color changed from black to gray, and then turned into brick red, orange red on the sample surface with reduction time changed. This phenomenon was attributed to the change of reduction products; With the reduction time increasing, the melting phenomenon of the particles on the surface of sample became intensive, which was accompanied with particle agglomeration.With the increase of device output power, the relative content of reduction products of Cu was increased first and then decreased, while the content of Cu₂O which is a inter phase was increased gradually; when output power was small, sample color was brownish red. With the power increasing, the red of sample surface became deeper. The reduction products would be re-oxidized if output power was too large; In the process of power increased, particles on surface melt and aggregated bit by bit. Sample surface left small holes when cooling and a new phase was formed from aggregation surface and then the surface of this phase was melt.In plasma conduct process, there was a completion about reduction and oxidation reaction. Active particles on the sample surface collided and sputtered in the reaction, while their energy transferred to the oxide particles to make the energy higher than the reaction activation energy and promote the reduction reaction.