Synthesis of Hydroxyapatite (HA) / Tri-Calcium Phosphate (TCP)
Composite Bioceramic Powders
and Their Sintering Behavior

 

    * N. Kivrak, M.Sc. Thesis, (Thesis Supervisor: Dr. A. Cneyt Tas), Dept. of Metallurgical and Materials Eng., METU, Turkey, June 1996.

    * N. Kivrak and A. Cuneyt TAS, "Synthesis of HA-TCP Composite Bioceramic Powders by Precipitation from Aqueous Solutions and Their Sintering Behavior," Journal of The American Ceramic Society, Vol. 81, 2245-2252 (1998).   (----> download pdf: ha-tcp-synthes.pdf)

    * N. Kivrak and A. Cuneyt TAS, "Synthesis of HA-TCP Composite Bioceramic Powders by Precipitation from Aqueous Solutions and Their Sintering Behavior," 98th Annual Meeting of the American Ceramic Society, Indianapolis, IN, USA, April 14-17, 1996.

    * N. Kivrak and A. Cuneyt TAS, "Synthesis of HA-TCP Composite Bioceramic Powders by Precipitation from Aqueous Solutions and Their Sintering Behavior," 3rd Ceramics Congress, Istanbul, Turkey, Turkish Ceramic Society, October 22-25, 1996. Download PDF

    * Patent Title: Production of Composite (Bi-phasic) Calcium Phosphate Bioceramics by using a Chemical Precipitation Technique, Patent Number: TR 1996 00469 B   (Turkish Patent Institute, Ankara), Date of Issue: May 21, 2001, Patent Inventor: Dr. A. Cuneyt TAS, Patent Owner: Middle East Technical University.
 

The two most important inorganic phases of synthetic bone applications, calcium hydroxyapatite (HA) and tri-calcium phosphate (TCP), were prepared as sub-micron, chemically homogeneous and high-purity ceramic powders, from calcium nitrate tetra-hydrate and di-ammonium hydrogen phosphate salts dissolved in aqueous solutions, by a chemical precipitation technique. It was observed that the synthesized precursors have reached a compound purity above 99% after 6 hours of calcination, in a dry air atmosphere, at 800C, following the drying at 100C. Produced HA and TCP ceramic powders were observed to be spherical in particle shape and to have an average particle size of 0.6-0.7 m. The most significant findings in the relevant literature on such phases, referred to be produced by other chemic al powder synthesis techniques, were their lack of high purity, and the possession of lower usable structural and chemical stability thresholds (below 1100C) to decomposition at high-temperatures. The pellets prepared from the powder compounds synthesize d in this study can be sintered in an air atmosphere up to 1500C, and they can still preserve their chemical structure and superior homogeneities. The chemical precipitation process employed was discovered to be useful for the synthesis of HA/TCP "composite (bi-phasic) powders, " for the first time, in one precipitation cycle.

The composite bioceramic powders were prepared with compositions of 20 through 90% HA (balance being the TCP phase) with 10% increments. The pellets prepared from the composite powders were sintered to almost full density in a dry air atmosphere at around 1200C. The phase evolution in the composite samples was studied by XRD as a function of temperature in the range of 1000 to 1300C. The sintering behavior of the composite bioceramics were studied by SEM.

The phase evolution behavior of the HA-TCP composite powders (all heated at 1200C, in air) synthesized were monitored by the below XRD diagrams:

 

Click on the figure areas to display the pics:


 
 
 
 

 

Researchers: Nezahat Kivrak and A. Cuneyt Tas (1994-1996).

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