Adhesion between Copper and Amorphous Silica: A Reactive Molecular Dynamics Study
S Urata and H Yoshino and M Ono and S Miyasaka and R Ando and Y Hayashi, JOURNAL OF PHYSICAL CHEMISTRY C, 122, 28204-28214 (2018).
Interactions between metals and oxide glasses are indispensable owing to their ubiquitous usages ranging from microelectronics to industrial production processes. In this study, adhesion between metal copper and amorphous silica (a-SiO2) was investigated as a primitive metal/oxide interaction by using reactive molecular dynamics simulations. According to uniaxial and shear deformation simulations on copper/a-SiO2 layered models, we found that adhesion between a-SiO2 and crystalline or amorphous copper layers is very weak. Indeed, the interlayer is the breakable surface because the fracture stress is much less than the yield stress of the matrix oxide. Contrarily, since a sufficiently oxidized copper layer binds stronger to a-SiO2, the fracture surface varies from the copper/a-SiO2 interface to in-between the oxidized/crystalline copper layers. It is concluded from the simulations that the oxidization improves adhesion between metals and oxide glasses for bonding processes, whereas it causes defects or impurities in the manufacturing process, because the oxidized layer eventually remains on oxide glass substrates. In addition, fracture simulations of composite models composed of copper nanoparticles and a-SiO2 were also performed to examine the effect of the inclusions on crack propagation. Because a thickness of a few nanometers of an oxidized layer was observed at the surface of the copper particle that precipitated in soda-lime silica glass, by scanning transmission electron microscopy with electron energy-loss spectroscopy, we investigated the influence of the oxidized layer on the fracture. Accordingly, it was found that the oxidized nanoparticle avoids stress concentration at the crack tip and eventually prevents crack propagation, because oxidization induces ductility in the interlayer of the composite. In summary, the degree of oxidization on the metal surface is an influential factor to control adhesion at the metal/oxide glass interlayer as well as the mechanics of the composite materials.
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