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Phase stability and rapid consolidation of hydroxyapatite-zirconia nano-coprecipitates made using continuous hydrothermal flow synthesis

Research output: Contribution to journalJournal article

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  • A.A. Chaudhry
  • H. Yan
  • G. Viola
  • M.J. Reece
  • J.C. Knowles
  • K. Gong
  • I. Rehman
  • J.A. Darr
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<mark>Journal publication date</mark>2012
<mark>Journal</mark>JOURNAL OF BIOMATERIALS APPLICATIONS
Issue number1
Volume27
Number of pages12
Pages (from-to)79-90
Publication StatusPublished
<mark>Original language</mark>English

Abstract

A rapid and continuous hydrothermal route for the synthesis of nano-sized hydroxyapatite rods co-precipitated with calcium-doped zirconia nanoparticles using a superheated water flow at 450°C and 24.1MPa as a crystallizing medium is described. Hydroxyapatite and calcium-doped zirconia phases in the powder mixtures could be clearly identified based on particle size and morphology under transmission electron microscopy. Retention of a nanostructure after sintering is crucial to load-bearing applications of hydroxyapatite-based ceramics. Therefore, rapid consolidation of the co-precipitates was investigated using a spark plasma sintering furnace under a range of processing conditions. Samples nominally containing 5 and 10wt% calcium-doped zirconia and hydroxyapatite made with Ca:P solution molar ratio 2.5 showed excellent thermal stability (investigated using in situ variable temperature X-ray diffraction) and were sintered via spark plasma sintering to >96% sintered densities at 1000°C resulting in hydroxyapatite and calcium-doped zirconia as the only two phases. Mechanical tests of spark plasma sintering sintered samples (containing 10wt% calcium-doped zirconia) revealed a three-pt flexural strength of 107.7MPa and Weibull modulus of 9.9. The complementary nature of the spark plasma sintering technique and continuous hydrothermal flow synthesis (which results in retention of a nanostructure even after sintering at elevated temperatures) was hence showcased. © The Author(s) 2012 Reprints and permissions.