Aerosol-gel-derived microcrystalline hydroxyapatite coatings
- PDF / 671,865 Bytes
- 8 Pages / 612 x 792 pts (letter) Page_size
- 53 Downloads / 181 Views
Langlet and C. Jime´nez Laboratoire de Mate´riaux et de Ge´nie Physique, UMR 5628, ENSPG-INPG, BP 46, Domaine Universitaire, 38402 Saint Martin d’He`res, France
P. Herrero Instituto de ciencia de Materiales, ICMM-CSIC, 28049 Madrid, Spain
E. Millonb) Groupe de Physique des Solides, Universite´s Paris VII-VI, UMR CNRS 7588, Tour 23, 2 Place Jussieu, 75251 Paris, Cedex 05, France (Received 20 September 2001; accepted 21 March 2002)
Highly porous microcrystalline hydroxyapatite (HAP) coatings have been prepared from calcium nitrate and phosphoric acid based sols by the aerosol-gel process. The coatings were studied after sintering at different temperatures with the use of Fourier transform infrared spectroscopy, x-ray diffraction, energy disperse x-ray microanalysis, scanning electron microscopy, and transmission electron microscopy. The composition, structure, and morphology of the coatings sintered at 650 °C fit fairly well highly porous HAP. These coatings were reproduced onto TiO2/Si substrates and studied by Rutherford backscattering. It is shown that even after chemical etching, an adherent calcium phosphate phase remains attached to the TiO2/Si substrate.
I. INTRODUCTION
The main objective of new generation structural biomaterials is to provide a rapid osseointegration as well as increased lifetimes of functional prostheses. Hydroxyapatite [HAP, Ca10(PO4)6(OH)2] bioactive coatings have provided a faster fixation of load bearing metallic or ceramic implants.1 Bulk HAP ceramics or composites could only be used for unstressed bone replacements due to their relatively poor mechanical properties.2 The success of bioactive HAP coatings requires restrictive physicochemical properties.3 The presence of amorphous phases or structures with a Ca/P molar ratio (Ca/P mr) different from the HAP stoichiometric value (1.67) leads to failure of the coating and implies further surgery.1 To control the stoichiometry, bioactive HAP coatings are generally submitted to sintering at temperatures higher than 900 °C. At lower temperatures the apatite structure is stable for coatings with a Ca/P mr different from stoichiometric HAP. High temperatures promote segregation mechanisms so that multiple phases appear if the calcium phosphate (CaP) coating is not stoichiometric HAP.4
a) b)
Address all correspondence to this author. Also at LSMCL, Universite´ de Metz, 57078 Metz Cedex 3, France.
1482
http://journals.cambridge.org
J. Mater. Res., Vol. 17, No. 6, Jun 2002 Downloaded: 16 Mar 2015
HAP coatings have been mainly prepared by the plasma spraying deposition technique, but detachment of so-formed coatings has been reported.5 The method implies temperatures over the fusion point so that porous coatings are not easily obtained and the metallic substrate is exposed to microstructural changes that affect the mechanical properties. Many alternative methods for the processing of HAP coatings have been reviewed.6 In the frame of sol-gel processing, HAP has been deposited by dip7–9 and spin10 coating and also processed in the form of po
Data Loading...
