Influence of preparation conditions on the microstructure and bioactivity of α-CaSiO3 ceramics: Formation of hydroxyapatite in simulated body fluid

Punnama Siriphannon, Yoshikazu Kameshima, Atsuo Yasumori, Kiyoshi Okada, Shigeo Hayashi

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Two different reagents, NaOH and NH4OH, were used to precipitate CaSiO3 precursor powders from ethanol solutions of Ca(NO3)2 · 4H2O and Si(OC2H5)4. The resultant powders of different Ca/Si ratio and residual Na2O content exhibited significant differences in the microtexture of the resulting sintered α-CaSiO3 ceramics. The microtexture of the ceramics from the NaOH system (CS-Na) contained smaller grain sizes and a thicker glassy phase at the grain boundaries than those produced using NH4OH (CS-NH). The CS-Na ceramics were soaked in a simulated body fluid (SBF) at 36.5°C for 2 h and 1, 5, 6, 10, 21, and 30 days while the CS-NH ceramics were soaked for 1, 5, 7, 15, 20, and 25 days using the same conditions. Hydroxyapatite (HAp) formed on the surfaces of both samples but at different formation rates due to differences in the microstructure. The CS-Na ceramics showed faster Hap formation because their smaller α-CaSiO3 grains dissolved more readily, allowing the calcium concentration in the SBF quickly to approach the appropriate condition for nucleation of Hap. In addition, the thicker glassy phase at the grain boundaries facilitated a faster formation of silanol on the surface of the amorphous SiO2 interlayer, a reaction that is considered to be a prerequisite for Hap formation. The formation of the Hap layer on the CS-Na ceramics therefore was very fast (12 μm/day), and their surfaces were covered completely within 5 days. A layer thickness of about 110 μm was achieved in 30 days, in contrast with the CS-NH ceramics, which took about 25 days to be fully covered with a 60-μm layer of Hap. (C) 2000 John Wiley and Sons, Inc.

Original languageEnglish
Pages (from-to)30-39
Number of pages10
JournalJournal of Biomedical Materials Research
Issue number1
Publication statusPublished - Aug 1 2000



  • Bioactive materials
  • CaSiO ceramics
  • Co-precipitation method
  • Hydroxyapatite
  • Simulated body fluid (SBF)

ASJC Scopus subject areas

  • Biomaterials
  • Biomedical Engineering

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