Electrophoretic deposition of composite hydroxyapatite–silica–chitosan coatings

Electrophoretic deposition (EPD) method has been developed for the fabrication of nanocomposite silica–chitosan coatings. Cathodic deposits were obtained on various conductive substrates using suspensions of silica nanoparticles in a mixed ethanol–water solvent, containing dissolved chitosan. Co-deposition of silica and hydroxyapatite (HA) nanoparticles resulted in the fabrication of HA–silica–chitosan coatings. The deposition yield has been studied at a constant voltage mode at various deposition durations. The method enabled the formation of coatings of different thickness in the range of up to 100 μm. Deposit composition, microstructure and porosity can be varied by variation of HA and silica concentration in the suspensions. It was demonstrated that EPD can be used for the fabrication of HA–silica–chitosan coatings of graded composition and laminates. The method enabled the deposition of coatings containing layers of silica–chitosan and HA–chitosan nanocomposites using suspensions with different HA and silica content. Obtained coatings were studied by X-ray diffraction, thermogravimetric and differential thermal analysis, scanning electron microscopy and energy dispersive spectroscopy. The mechanism of deposition is discussed.