The Study Of Cu/γ-Al₂O₃ Coherent Interfaces By First Principles Calculations

The property of materials is influenced by the interfaces.The coherent relationship of interfaces is an important element to have the high strength toughness materials.It is very significant to study physical essence of interfaces and develop new high strength toughness materials from the view of Electronic structures.The CuAl₂O₃ composite is a kind of oxide particles reinforced Cu-base composites with the advantages of excellent conductivity and thermal conduction,the high temperature softening resistance property,great malleability and has extensive application foreground.The performance of Cu-Al₂O₃ composites can be improved and increased through the theory calculation and analysis of interfaces.It has very high theoretical value.In this paper,the Cu/γ-Al₂O₃ coherent interfaces were studied by the first principles calculation.Lattice constants and electronic structures of Cu and γ-Al₂O₃ were respectively calculated and studied.What is more,the models of coherent interfaces between the low-index surfaces of Cu and γ-Al₂O₃ were built.Through calculating and analyzing the work of separation and interface distances,the most stable interface structure was confirmed.Cu-Al₂O₃ composites were prepared by the method of powder internal oxidized.By studying the interface miscrostructure,the phase relationship was founded.It was be compared between calculation result by first-principles and analysis result by experiment.The point groups of Cu and γ-Al₂O₃ both were Fm-3m and the structure of them was face-centered cubic.The optimizing and calculative results showed that: the lattice constants of Cu and γ-Al₂O₃ were 0.364 nm and 0.393 nm respectively.Through calculating the density of states of two kinds of materials,it indicated that the conduct capacity of Cu was contributed by d,s,p orbital electron.For the γ-Al₂O₃,the top of valence band touched the bottom of valence band.The bonding electrons were on the orbit of O2 s and Al3 s,O2p and Al3 p respectively.In this study,the models of Cu（100）/γ-Al₂O₃（100）,Cu（011）/γ-Al₂O₃（100）,Cu（111）/γ-Al₂O₃（100）,Cu（100）/γ-Al₂O₃（110）,Cu（011）/γ-Al₂O₃（110）and Cu（111）/γ-Al₂O₃（110）coherent interfaces were built.In consideration of the different situations whether Cu atom was on the top of O atom or Al atom,there were 12 interface models.Through relaxation and majorization,the structure of Cu（011）/γ-Al₂O₃（110）（Cu-O）was the most stable one.The work of separation was the biggest and was 7.6 J/m².At the same time,the distance was the shortest and was 0.16 nm.The microstructures analysis of samples showed that the relationship between Cu（011）and γ-Al₂O₃（110）was coherent.The results of first principles calculation were consistent with those of observations.Through modeling and calculating the Cu/γ-Al₂O₃ coherent interfaces,the microstructures of them were analyzed.And the study explained the experiment phenomenon to some extent,supported the experiment result on theory and will play a guiding role in the further experiment research.