title: Formation of hydroxyapatite layer on bioactive Ti and Ti-6Al-4V by simple chemical technique.
abstract: Bioactive coatings on cp-Ti and Ti-6Al-4V were prepared by a simple chemical technique. Specimens of cp-Ti and Ti-6Al-4V were initially immersed in a 5 M NaOH solution at 60 degrees C for 24 h which resulted in the formation of a porous network structure composed of Na2Ti5O11 and TiO2. The specimens were then immersed in a Ca-rich solution either at 60 degrees C or at 36.5 degrees C for 24 h. During this treatment Na+ was released and Ti-OH groups were formed. Subsequently, TiO2 dissociated from the Ti-OH group and combined with calcium ions to form calcium titanate (CaTiO3), which was embedded in a titania gel layer during the immersion period. The specimens were then immersed in r-SBF at 36.5 degrees C for 1-30 days. After immersion in r-SBF for 3 days, HAp (hydroxyapatite) spheroids began to deposit on the substrates, and within a week the surfaces were covered. The HAp spheroids were 5 microm in size with a Ca/P ratio of 1.68 which was close to bone-like apatite (1.67). The average thicknesses of HAp layer after immersion in r-SBF for 3 days, 1 week, and 2 weeks were 3.8, 5.6, and 6.4 microm, respectively. A scratch test, used to evaluate the adhesive strength of the HAp layer, showed that the HAp layer was not scraped off until the applied load reached 26 N.
authors.affiliation: Nagaoka University of Technology, 1603-1 Kamitomioka, Nagaoka-shi, 940-2188, Japan.
authors.forename: Achariya
authors.initials: A
authors.lastname: Rakngarm
authors.forename: Yukio
authors.initials: Y
authors.lastname: Miyashita
authors.forename: Yoshiharu
authors.initials: Y
authors.lastname: Mutoh
mesh_terms: D000497:Alloys / Q000737:chemistry*; D001031:Apatites / Q000737:chemistry; D002118:Calcium / Q000737:chemistry; D017610:Calcium Compounds / Q000737:chemistry; D017886:Durapatite / Q000737:chemistry*; D007477:Ions; D008422:Materials Testing; D008956:Models, Chemical; D010087:Oxides / Q000737:chemistry; D012972:Sodium Hydroxide / Q000737:chemistry; D013499:Surface Properties; D013696:Temperature; D013718:Tensile Strength; D013997:Time Factors; D014025:Titanium / Q000737:chemistry*
chemical_list: D000497:Alloys; D001031:Apatites; D017610:Calcium Compounds; D007477:Ions; D010087:Oxides; C528635:titanium aluminum alloy; C059910:perovskite; C009495:titanium dioxide; D012972:Sodium Hydroxide; D017886:Durapatite; D014025:Titanium; D002118:Calcium