Abstract :
A range of potentially bioactive ceramic
coatings, based on combinations of either hydroxyapatite
(HA) or titanium oxide nanoparticles with
carbon nanotubes (CNTs), have been deposited on
metallic substrates, using electrophoretic deposition
(EPD). Sol–gel derived, ultrafine HA powders (10–
70 nm) were dispersed in multi-wall nanotube-containing
ethanol suspensions maintained at pH = ~3.5
and successfully coated onto Ti alloy wires at 20 V for
1–3 min For TiO2/CNT coatings, commercially available
titania nanopowders and surface-treated CNTs in
aqueous suspensions were co-deposited on stainless
steel planar substrates. A field strength of 20 V/cm
and deposition time of 4 min were used working at
pH = 5. Although the co-deposition mechanism was
not investigated in detail, the evidence suggests that
co-deposition occurs due to the opposite signs of the
surface charges (zeta potentials) of the particles, at the
working pH. Electrostatic attraction between CNTs
and TiO2 particles leads to the creation of composite
particles in suspension, consisting of TiO2 particles
homogenously attached onto the surface of individual
CNTs. Under the applied electric field, these net
negatively charged ‘‘composite TiO2/CNT’’ elements
migrate to and deposit on the anode (working electrode).
The process of EPD at constant voltage
conditions was optimised in both systems to achieve
homogeneous and reasonably adhered deposits of
varying thicknesses on the metallic substrates.
