Study On The Sintering Behavior And Mechanical Properties Of HA Ceramics And Its Composites

Hydroxyapatite(HA) ceramics exhibit a good bioactivity and biocompatibility. Controlling the mechanical properties of HA ceramics is a key factor on its application in biomedical field. In the present paper, the effect of the physical properties of original powders and glass additives on the sintering behavior and mechanical properties of HA ceramics were investigated. HA powders with different morphologies were synthesized, using PVP(polyvinylpyrrolidone) and CTAB(cetyltrimethylammonim bromide) as template, respectively. Under different temperatures, HA powders and glass/HA composites were sintered. Phase, morphologies, microstructures and mechanical properties of both HA powders and ceramics were characterized, using XRD, TEM, FESEM, DSC/TGA, respectively. The conclusions are as follows:1. The powders templated by PVP are irregular nanorods, with a mean length of～100nm, a mean diameter of～20nm. While the powders templated by CTAB are submicron prisms like, with a mean length of～200nm, a mean width of～200nm. The difference in morphology is attributed to the different contact mechanism between the templates and the reagents.2. Both the HA powders exhibit a high thermal stability. The Vickers hardness and bending strength are high if the relative density is high, showing that the mechanical properties of HA ceramics are highly depend on the density. Furthermore, the ceramics prepared from CTAB templated HA powders show a higher density than the ceramics prepared from PVP templated HA powders, leading to a better mechanical properties.3. Glass powders additives cause a severe decomposition of HA. The thermal stability of HA ceramics depends on both the chemical composition of glass powders and the physical properties of the raw HA powders. The PVP templated HA powders show a high reacitivity with the glass due to its high specific surface area, resulting a low density. The glass powders containing MgO stabilize the Whitlockite (the decomposition products of HA). Additionally, in comparison with the glass powders containing ZnO, the glass powders containing MgO show an optimistic effect on the accelerating the densification of HA powders. The mechanical properties are affected by the amount of second phase and grain size. Specificly, the second phase improves the fracture toughness, while the grain growth deteriorates the mechanical properties of HA ceramics.