Influence of defects in sp2-bonded network of diamond-like carbon on silica scale adhesion in geothermal power plants

Silica scale adhesion onto geothermal power plant equipment reduces the power efficiency. In our previous study, diamond-like carbon (DLC) coatings with low sp2 fractions and high hydrogen contents were found to suppress silica adhesion. Therefore, the present study was aimed at clarifying the mechanism of silica adhesion onto the sp2-bonded network of DLC. In-lens scanning electron microscopic imaging of silica adhered onto defective graphene indicated that the adhesion occurred on defects in the sp2-bonded network. First-principles calculations revealed that the graphene with hydrogen-terminated defects exhibited reduced adsorption energy between silica and the sp2-bonded network. Overall, the simulations and experiments helped establish a silica adhesion model in which defects in the sp2-bonding network of DLC behave as silica adhesion sites