Synthesis and characterization of carbonated hydroxyapatite as bioceramic material
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Date
2009
Authors
Widyastuti
Journal Title
Journal ISSN
Volume Title
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Abstract
Carbonated hydroxyapatite (CHA) was synthesised from two synthesis
routes, which were the precipitation method and nano-emulsion method. The
carbonate content in the solution was varied with CO3
2-/PO4
3- ratio of 1, 3, 5 and 7,
while pH and Ca/P ratio were constant at 11 and 1.67 respectively. Vacuum
filtration and drying was used in the synthesis process to obtain the CHA powder.
Heat treatment at different temperatures, which were 600, 700, 800 and 900oC, in
flowing CO2 gas were performed to the powder to analyse the thermal stability.
Moreover, bulk CHA was prepared by pressing method, followed by carbonation to
produce the ceramic part from the powder for further application. The molding
pressure and carbonation time were varied during the preparation of bulk CHA.
All the synthesised powder was found to produce B-type CHA, which is the
preferred substitution type in biological bone, in nanometer size of the range 20-35
nm. Based on the results obtained, the carbonate content was found to influence the
properties of the CHA powder. With high CO3
2-/PO4
3- ratio of 7, it was found that
the secondary phase of calcite had formed. The powder with high carbonate content
also had low thermal stability during heat treatment, which leads to formation of
CaCO3 and CaO phases. On the other hand, CHA powder with CO3
2-/PO4
3- ratio of
1 had produced single phase CHA with the Ca/P ratio close to biological bone. It
also has high thermal stability, reaching 900oC. CHA powder with this composition,
having low CO3
2-/PO4
3- ratio, showed no evident of secondary face formation during
heat treatment although some of the carbonate group was found to move to A-sites
during the heat treatment. The compaction pressure of bulk CHA also played
important role in the mechanical properties. Bulk CHA that was prepared with
molding pressure of 8 MPa and 72 hours of carbonation showed optimum DTS
value at 1.68 MPa. The formation of apatite layer occurred in the bulk CHA after
soaking in SBF solution for 14 days. This indicated that the CHA synthesised in this
study has a good biocompatibility with sufficient strength to be applied as bone
substitute in non-load bearing areas.
Description
Master
Keywords
Chemical science , Carbonated hydroxyapatite , Bioceramic material