Lee Su-Hee, Kim Hyoun-Ee, Kim Hae-Won
School of Materials Science and Engineering, Seoul National University, Seoul, 151-744, Korea.
J Mater Sci Mater Med. 2008 May;19(5):1905-11. doi: 10.1007/s10856-007-3260-x. Epub 2007 Oct 4.
In the apatite coatings on Ti the heat treatment process is necessary to crystallize the apatite structure for improved chemical stability and biological properties. However, the heat treatment normally degrades the mechanical strength of the coating layer associated with thermally induced stress. In this study, we aimed to improve the crystallization of apatite coating by using calcium fluoride (CaF2) as a buffer layer. The insertion of a thin layer of CaF2 (0.2-1 microm) between apatite and Ti significantly improved the crystallization behavior of apatite. Moreover, this crystallization was more enhanced as the thickness of CaF2 was increased. When a 1 microm-thick CaF2 was inserted, the crystallization of apatite initiated at a temperature as low as 320 degrees C, being a dramatic improvement in the crystallization when considering the crystallization initiation temperature of a bare apatite coating on Ti was approximately 450 degrees C. As a result of this crystallization enhancement, the dissolution behavior of CaF2-inserted apatite coatings was more stable than that of the bare apatite coating, showing much reduced initial-burst effect. Preliminary cellular assay showed the CaF2-inserted apatite coating provided a substrate for cells to spread and grow favorably, as being similar to the bare apatite coating. This novel way of apatite coating on Ti using CaF2 buffer layer may be useful in the coating systems particularly requiring low temperature processing and increased crystallinity with high chemical stability.
在钛表面的磷灰石涂层中，热处理过程对于使磷灰石结构结晶以提高化学稳定性和生物学性能是必要的。然而，热处理通常会降低与热诱导应力相关的涂层机械强度。在本研究中，我们旨在通过使用氟化钙（CaF2）作为缓冲层来改善磷灰石涂层的结晶。在磷灰石和钛之间插入一层薄的CaF2（0.2 - 1微米）显著改善了磷灰石的结晶行为。此外，随着CaF2厚度的增加，这种结晶得到进一步增强。当插入1微米厚的CaF2时，磷灰石的结晶在低至320℃的温度下开始，考虑到钛上裸磷灰石涂层的结晶起始温度约为450℃，这在结晶方面是一个显著的改善。由于这种结晶增强，插入CaF2的磷灰石涂层的溶解行为比裸磷灰石涂层更稳定，初始爆发效应大大降低。初步细胞试验表明，插入CaF2的磷灰石涂层为细胞提供了一个有利的铺展和生长基质，与裸磷灰石涂层相似。这种使用CaF2缓冲层在钛上进行磷灰石涂层的新方法可能在特别需要低温处理和具有高化学稳定性的增加结晶度的涂层系统中有用。
