title: Surface modification for titanium implants by hydroxyapatite nanocomposite.
abstract: BACKGROUND
  Titanium (Ti) implants are commonly coated with hydroxyapatite (HA). However, HA has some disadvantages such as brittleness, low tensile strength and fracture toughness. It is desirable to combine the excellent mechanical properties of ZrO2 and the chemical inertness of Al2O3 with respect to the purpose of this project which was coating Ti implants with HA-ZrO2-Al2O3 to modify the surface of these implants by adding ZrO2 and Al2O3 to HA. The purpose of this study was to evaluate the efficacy of hydroxyapatite coating nonocomposite.
  
  
  METHODS
  From September 2009 to January2011, functionally graded HA-Al2O3-ZrO2 and HA coatings were applied on Ti samples. HA-Al2O3-ZrO2 and HA sols were orderly dip coated on the substrates and calcined. Scanning electron microscopy and EDS were used to estimate the particle size of the surfaces and for morphological analysis. The morphology of non-coated HA-coated HA-Al2O3-ZrO2 (composite-coated) and double-layer composite coated samples were compared with one other. Mechanical test (heat & quench) was also done for comparing single-phase (HA), composite and double-layer composite samples.
  
  
  RESULTS
  The morphology of HA-Al2O3-ZrO2 coating is more homogenous than HA-coated and uncoated samples. Furthermore, single-layer coating is more homogenous than double-layer coating. EDS analysis was done on HA-coated sample and showed that the Ca/P ratio in the film was similar to the theoretical value 1.67 in HA.
  
  
  CONCLUSIONS
  Surface modification of Ti implants can be done by coating them with single-layer of HA-Al2O3-ZrO2. Single-layer hydroxyapatite-alumina-zirconia coated sample has the most homogenous morphology on the surface.
authors.affiliation: Department of Materials Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran.
authors.forename: Roxana
authors.initials: R
authors.lastname: Family
authors.forename: Mehran
authors.initials: M
authors.lastname: Solati-Hashjin
authors.forename: Shahram
authors.initials: S
authors.lastname: Namjoy Nik
authors.forename: Ali
authors.initials: A
authors.lastname: Nemati
keywords: Hydroxyapatite; Nanocomposite; Surface modification; Ti Implants