ディオプサイド表面に析出するハイドロキシアパタイトの成長機構

抄録

In this study, we ultra structurally evaluated the interface between granular diopside and diopside-induced hydroxyapatite (HAp), and presented a growth mechanism of HAp at the surface of diopside.Specimens were prepared in the following two experiments.
1) Granular diopside immersed in the simulated body fluid for 5 days.
2) Granular diopside implanted into the rabbit bone cavity and left for 1 month.
In the first step, epitaxial crystal growth of octacalcium phosphate (OCP) occurs in the diopside surface layer.The epitaxial relationship of OCP on diopside are as follows,
(001) _di// (010) _ocp
[110] _di, // [100] _ocp
The lattice mismatch between the c-axis of OCP and [110] of diopside is 3.7% whereas between the a-axis of OCP and three times of [110] period of diopside is 0.05%.
In second step, OCP changed to HAp by topotactic phase transition. The topotactic relationship between OCP and HAp are as follows,
a_ocp=2a HAp
b_ocp=b_HAp
c_ocp=c_HAp
In the early period, HAp crystals observed were platelet-shaped.It is influecned considerably by the shape of OCP. HAp grows into a hexagonal prism shape.