Effect of Cr and Zn nuclei on demolding performance of Cu/Ni composite in precision electroforming
Spraying K2Cr2O7 on the mould surface is one effective method to facilitate electroforming release.However,it is important to note that Cr6+is known to be highly carcinogenic.In this paper,the electrodeposition method is used to prepare Cr nuclei and Zn nuclei as an alternative to the Cr6+passivation layer to create a low-toxicity anti-adhesive layer consisting of Cr3+oxides and non-toxic Zn2+passivates.The current-time curves of Cr3+and Zn2+are measured by the chrono-current method.SEM,EDS and XPS tests are carried out on Cu-Cr and Cu-Zn surfaces to analyze the surface morphology,surface elemental composition and content after electrodeposition of Cr3+and Zn2+nuclei.Additionally,contact angle tests are carried out on Cu,Cu-Cr and Cu-Zn surfaces,and the surface energy of polycrystalline Cu with Cr3+and Zn2+nuclei was calculated based on surface energy theory.The rsearch shows that the nucleation of Cr3+and Zn2+at Cu electrodes is consistent with transient nucleation.The distribution of Cr3+nuclei on the Cu surface is more uniform and has a more regular shape compared to Zn2+nuclei.Moreover,Cr and Zn nuclei both form oxides on the Cu surface,and the content of Cr2O3 is significantly higher than that of ZnO.The surface energies of polycrystalline Cu,Cu-Cr and Cu-Zn are in the following order:polycrystalline Cu＞Cu-Zn＞Cu-Cr,and the difference in surface roughness between Cu and Ni after demolding with the assistance of Cr3+and Zn2+oxides are 57.14％and 64.52％,respectively.Therefore,trivalent Cr oxides are more effective in facilitating the smooth demolding of Cu/Ni composites.
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