The effect of cationic surfactant-assisted electrochemical co-deposition on diamond wire surface

Surfactants are a key factor in the preparation of electroplated diamond wires. While their influence mechanism is generally believed to be dominated by charge electrophoresis in electrochemical co-deposition, our study reveals that the adsorption energy also acts as an important influencing mechanism in this process. In this study, four different types of cationic surfactants (CTAC, DMDAAC, PDDA, CHEC) are selected to represent cationic monomers, monomers containing carbon‑carbon double bonds, polymers, and chemically modified polymers, respectively. Co-deposition of nickel and diamond (D50 = 4.3 μm and 35.6 μm) onto the tungsten wire substrate was achieved under identical electrochemical parameters. The underlying mechanism was investigated by integrating experimental characterization and molecular dynamics simulations. The results indicate that different surfactants significantly influence the diamond embedding density, and this discrepancy varies with diamond particle size. For fine diamond particles (4.3 μm), the embedding effectiveness correlated positively with the particle electrophoretic mobility. For coarse diamond particles (35.6 μm), the embedding effectiveness was dominated by the surface adsorption energy. Cationic surfactants regulate the electrophoretic migration of particles through charge reversal and influence adsorption consolidation via the interactions between their molecular structure and diamond crystal surface, which synergistically determine the diamond embedding effectiveness.