BIOCERAMIC MANUFACTURING TECHNIQUES

39.6.3 Hydroxyapatite Synthesis Method

Prepare the following solutions: Solution 1 : Dissolve 157.6 g calcium nitrate letrahydrate [Ca(NO 3 ) 2 4H2O] in 500

ml DI water. Bring the solution to a pH of 11 by adding 70 ml ammonium hydroxide [NH 4 OH]. Bring the solution to 800 ml with DI water.

Solution 2 : Dissolve 52.8 g ammonium phosphate dibasic [(NH 4 ) 2 HPO 4 ] in 500 ml DI water. Bring the solution to a pH of 11 by adding 150 ml ammonium hydroxide [NH 4 OH]. Add Dl water until the precipitate is completely dissolved. 250-350 ml.

39.6.3.1 Special Note. If you use calcium nitrate [Ca(NO 3 ) 2 .nH2O] instead of calcium nitrate tetrahydrate you need to recalculate the amount of calcium nitrate to add to make

Solution 1 on the basis of the absence of the extra four waters. If you do not, you will have to add a large amount of ammonium hydroxide to pH the solution:

1. Add one-half of Solution 1 to a 2 l separatory funnel

2. Add one-half of Solution 2 to a 2 l separatory funnel

3. Titrate both solutions into a 4 l beaker with heat and constant stirring

4. Boil gently for 30 min

5. Repeat steps l - 4 for the rest of Solutions 1 and 2

6. Let cool completely allowing precipitate to settle to bottom of beaker

7. Pour contents of beaker into 250 ml polypropylene bottles

8. Centrifuge bottles for l0 min at (10,000 rpm) 16,000 g

9. Collect precipitate from the six bottles into two and resuspend with DI water

10. Fill the four empty bottles with the reaction mixture and centrifuge all six as before

11. Collect precipitant from the two bottles that were resuspended with DI water

12. Combine remaining four bottles into two bottles and resuspend with DI water

13. Repeat steps 10 - 12 as necessary

14. Dry precipitate for 24 - 48 h at 70°C

15. Calcine the precipitate for one hour at 1140°C

16. Grind and sieve product as desired