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Home  >  Journal list  >  Journal of the Ceramic Society of Japan  >  Vol.117  No.1363 (March) (2009)  >  pp.363-368

Journal of the Ceramic Society of Japan
<<Previous article Vol.117  No.1363 (March) (2009)   pp.363 - 368 Next article>>

Effect of colloidal silica addition on the formation of porous spherical α-calcium orthophosphate agglomerates by spray pyrolysis technique

Kiyoshi ITATANI1), Ari OOE1), Ian J. DAVIES2), Tomohiro UMEDA1), Yoshiro MUSHA3) and Seiichiro KODA1)
1) Department of Materials and Life Sciences, Sophia University
2) Department of Mechanical Engineering, Curtin University of Technology
3) Department of Orthopaedic Surgery, School of Medicine, Toho University


  The effect of colloidal silica (SiO2; CS) addition on the formation of porous spherical α-calcium orthophosphate (α-Ca3(PO4)2; α-TCP) agglomerates has been examined. The starting powder was prepared by the spray pyrolysis of calcium phosphate (Ca/P ratio = 1.50) solution containing 0.9 mol·dm-3 Ca(NO3)2, 0.6 mol·dm-3 (NH4)2HPO4, CS (mean particle size; 14, 24 and 39 nm) and concentrated HNO3 at 600°C, using an air-liquid nozzle; the amounts of CS in the spray-pyrolyzed powder were adjusted to be 0.1-0.4 mass%. The heat-treatment of spray-pyrolyzed power with 0.4 mass% of CS addition at 1200°C for 10 min showed that the transformation from β- to α-TCP was restricted as the diameter of CS decreased from 24 to 14 nm. The heat-treatment of spray-pyrolyzed powder containing 0.1 mass% of CS (mean diameter: 24 nm) at 1200°C for 10 min resulted in not only the complete transformation of β- to α-TCP but also preservation of original spherical framework. The immersion of porous spherical α-TCP agglomerates in simulated body fluid (SBF) brought about the rapid formation of hydroxyapatite, due to higher specific surface area (17.0 m2·g-1) compared to that of commercial powder (10.9 m2·g-1). The hardened body with the porosity of 66.3% could be fabricated by mixing the calcium-phosphate paste with 50 mass% of the present porous α-TCP agglomerates, using the malaxation liquid. Immersion of this hardened body in SBF at 37.0°C resulted in the formation of hydroxyapatite within three days.


Keyword:
Spray pyrolysis technique, Colloidal silica, Porous spherical α-calcium orthophosphate agglomerates, Calcium-phosphate paste

Received: December 01, 2008
Accepted: January 15, 2009 , Published online: March 01, 2009
Copyright (c) 2009 The Ceramic Society of Japan

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