Study On The Oxidation Behavior Of Single Crystal Copper

With the maturity of the heated mould continuous cast equipent and the improvment of drawn equipent of single crystal copper, single crystal copper has been walked out of the laboratory and into the industrial mass production and application of stage. Compared with polycrystalline copper, the single crystal copper has been widely used in audio and video wires and the connective wires of semi-conductive encapsulation for its more excellent electrical conductivity, thermal conductivity and better plastic deformation.However, being easily oxidized weaken the copper's quality and performance.Thermodynamics of copper oxidation, Oxidation mechanism and Oxidation kinetics were studied in this thesis. Among the rest, The thermodynamics of copper oxide was studied by calculating the Gibbs free energy changeΔG, entropy change AS and oxide decomposition pressure at a Continuous temperature range and drawed its curves by using Matlab. Compared with the differences of constructure between the single crystal copper and polycrystalline copper,the mechanism of single crystal copper oxide was studyed by combinating the EDS and oxide film morphology and analysising the atomic energy of copper surface. By using the oxidation weight gain in the experiment,calculating the increasing weight rate to draw its curves the Kinetics of oxidation of single crystal copper was studied.The results of this study show that the copper oxidation is a spontaneous reaction and it has the ability to happen at the room temperature. When the temperature rises,it is not inconsistent that the trend of copper oxide will decrease and the reaction rate of copper oxidation will increase. The most easily generate and the most stable oxidation products are Cu2O on the thermodynamics,but Cu2O is not the final oxidation products.The higher the atomic energy of copper surface the easier chemical adsorption reaction happen between the copper atom and oxygen molecules. At the beginning, the stable Cu2O on the thermodynamics does not generate, but the formation of amorphous organization of copper and oxygen. With the development of copper oxidation the Loose crystalline particles of Cu2O does not form untill the free electrons atoms of copper will shift further to the Oxygen ions. The oxidation continuing, the Cu2O is oxided to CuO gradually in the process. At first, the thin strip of CuO crystals form on the surface of Cu2O and continue to grow thincker. forming dense CuO film and the copper ion diffusion into the speed control phase.Study on the Oxidation Kinetics of single crystal copper show that the oxidation of copper largely depend on the temprature and the atomic energy of copper surface.The atomics of copper surface which have the larger energy have the faster oxidation speed and the order of the atomic planes oxidation rate is(100)>(110)> grain boundary atoms>(111). The Results are consistent with the theoretical analysis. Although the temperature, the purity will affect the oxidation rate of copper, at higher temperatures,the higher purity the lower oxidation rate.