Synthesis of Apatite Ceramics with Preferential Crystal Orientation
Synthesis of Apatite Ceramics with Preferential Crystal Orientation
复制标题
择优晶体取向磷灰石陶瓷的合成
DOI：
--
复制
发表时间：
2004
期刊：
影响因子：
--
通讯作者：
Y. Umakoshi
中科院分区：
文献类型：
--
作者：
T. Nakano;W. Fujitani;Y. Umakoshi
生物硬组织中生物磷灰石（apatite, BAp）晶体的c轴取向取决于其在体内的形状和应力分布，而用于植骨的磷灰石基生物陶瓷则没有BAp取向。因此，可以控制晶体取向，以开发具有类似生物硬组织的磷灰石（Ap）纹理的新型生物陶瓷。由于牛股骨的皮质部分沿长骨的纵向方向呈现一维取向，因此以股骨为起始材料，研究了热处理对Ap取向的影响。首先在600°C下进行热处理1h以去除有机成分，然后在700°C至1300°C之间的每个温度下进行热处理。用微束x射线衍射仪测定了BAp的晶体取向和织构。在600℃热处理1h后，Ap陶瓷的晶粒尺寸明显增大，并保留了大量的孔隙以换取有机成分。多个Ap晶粒被孔隙包围成一组，但在高达900℃的温度范围内进行额外热处理，使组内Ap晶粒数量减少，最终在1000℃时成为单一晶粒区。孔隙密度随退火温度的升高而降低，尤其是在1000℃以上。在整个热处理过程中，Ap中c轴的一维优先排列都保持不变，且随着退火温度的升高，这种排列的程度有所增加，这是因为在起始材料中存在大量与c轴相对的低能低角边界，并优先保留在合成的Ap陶瓷中。因此，对牛股骨进行适当的热处理可以使Ap陶瓷具有优先的晶体取向。
Biological hard tissues show preferential alignment of the c-axis of biological apatite (BAp) crystallites depending on the shape and stress distribution in vivo, but apatite-base bioceramics developed for bone grafting have no preferential BAp orientation. Thus, the crystal orientation was controlled for developing novel bioceramics with apatite (Ap) texture similar to biological hard tissues. Since cortical portion in a bovine femur shows a one-dimensional orientation along the longitudinal direction of long bone, the effect of heat treatment on Ap orientation was investigated in the femur bone as a starting material. Heat treatment was performed first at 600°C for 1h to remove organic constituents and subsequently at each temperature between 700°C and 1300°C. Crystal orientation and texture of BAp were measured by the micro-beam X-ray diffractometer. Size of BAp crystallites increased remarkably after a heat treatment even at 600°C for 1h and a great amount of pore remained in the Ap ceramics in exchange for the organic constituents. Several Ap grains were surrounded as a group by the pores, but additional heat treatment in a temperature range up to 900°C reduced the number of Ap grains in the group, and finally became a single grain region at 1000°C. Pore density decreased with increasing annealing temperature, especially above 1000°C. One-dimensional preferential alignment of the c-axis in Ap maintained during all the heat treatment and the degree increased with increasing annealing temperature because a lot of low-energy low angle boundaries against the c-axis existed in the starting material and preferentially remained in the synthesized Ap ceramics. It was therefore concluded that adequate heat treatment of bovine femur can give the preferential crystal orientation in Ap ceramics.