title: Critical ageing of hydroxyapatite sol-gel solutions.
abstract: It has been established that hydroxyapatite coatings can be produced using an alkoxide based sol-gel technique. Previous work showed that in addition to hydroxyapatite other phases including CaO were observed. A critical factor in determining the composition of the final coating is the period between solution preparation and coating deposition. The current study addresses how the ageing time affects the composition of the coating and the time required before a solution can be used to deposit monophasic coatings. Powders and coatings were produced with ageing times up to one week and examined with X-ray diffraction, thermal gravimetric analysis and differential thermal analysis. By depositing coatings after various ageing times, it was found that a solution ageing time of at least 1 day was required before monophasic hydroxyapatite coatings could be deposited. Thermogravimetric analysis showed that heating of the gel in air or in nitrogen both produced hydroxyapatite. Thermogravimetric analysis could be used as a simple and effective tool for identifying the critical ageing time required to produce high-purity hydroxyapatite coatings.
authors.affiliation: Department of Chemistry, Materials and Forensic Sciences, University of Technology, Sydney, Broadway, NSW, Australia.
authors.forename: C S
authors.initials: CS
authors.lastname: Chai
authors.forename: K A
authors.initials: KA
authors.lastname: Gross
authors.forename: B
authors.initials: B
authors.lastname: Ben-Nissan
mesh_terms: D001672:Biocompatible Materials; D017610:Calcium Compounds; D015921:Dental Implants; D005782:Gels; D006358:Hot Temperature; D006882:Hydroxyapatites / Q000737:chemistry*; D009984:Orthopedic Fixation Devices; D010087:Oxides; D011208:Powders; D012996:Solutions; D013816:Thermodynamics; D013997:Time Factors; D014961:X-Ray Diffraction
chemical_list: D001672:Biocompatible Materials; D017610:Calcium Compounds; D015921:Dental Implants; D005782:Gels; D006882:Hydroxyapatites; D010087:Oxides; D011208:Powders; D012996:Solutions; C016538:lime