CO₂ gas-activated sintering of carbonated hydroxyapatites

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• 作者：Z. Zyman ; M. Tkachenko
• 关键词：Carbonated hydroxyapatite ; Firing
• 刊名：Journal of the European Ceramic Society
• 出版年：2011
• 出版时间：March 2011
• 年：2011
• 卷：31
• 期：3
• 页码：241-248
• 全文大小：584 K

文摘

Sintering compacts of carbonated hydroxyapatite (CHA) nanoparticles (3.4 wt % CO₃²⁻) in a CO₂ flow (4 mL/min) proceeded at a temperature which was more than 200 °C lower than that for hydroxyapatite in air (1150 °C). During heating from RT to 1200 °C (5 K/min) the rate of shrinkage of the CHA compacts showed a maximum thrice as high as that in air at about 929 °C. The shrinkage correlates with a mass loss caused by the release of CO₂ due to the thermal decomposition of CO₃²⁻ ions that substitute PO₄³⁻ ions in the CHA lattice. Firing the compacts in the CO₂ flow at 800 and 900 °C for 2 h resulted in an additional carbonatation on the B-sites and a further decrease in the sintering temperature to 890 °C. The compacts fired in the 900–1000 °C range became almost complete ceramics with high densities and mechanical properties close to those of medical implants. Firing at temperatures above 1000 °C resulted in an additional carbonatation on the A-sites. However, this led to a material with low densities and poor mechanical properties. A supposition has been proposed that the effect of CO₂ gas-activated sintering is a result of the intensification of the diffusion in the nanoparticles caused by CO₂ molecules entering the bulk from the CO₂ atmosphere and (or) releasing from the bulk due to the decomposition of carbonates on the B-sites in the lattice.