Laboratoire des Matériaux Inorganiques, CNRS UMR 6002, Universite Blaise Pascal & Ecole Nationale Supérieure de Chimie de Clermont-Ferrand, Clermont Université, 24 avenue des Landais, Aubière Cedex, France.
ACS Appl Mater Interfaces. 2009 Feb;1(2):505-13. doi: 10.1021/am800162a.
Sol-Gel chemistry has been used to prepare undoped and Mg-substituted biphasic calcium phosphate (BCP) ceramics composed of hydroxyapatite (HAp) and whitlockite (beta-TCP) phases. Different series of samples have been synthesized with different Mg-doping levels (from 0 to 5 atomic % of Ca atoms substituted) and different temperatures of calcination (from 500 to 1100 degrees C). All of the powdered samples were systematically treated by Rietveld refinement to extract the quantitative phase analysis and the structural and microstructural parameters, to locate the Mg crystallographic sites, and to refine the composition of the Mg-substituted phases. The temperature dependence of the weight amount ratio between HAp and beta-TCP is not monotonic because of the formation of minor phases such as Ca(2)P(2)O(7), CaO, MgO, and CaCO(3) and certainly an amorphous phase. On the other hand, the Mg stabilizing feature on the beta-TCP phase has been evidenced and explained. The mechanism of stabilization by small Mg(2+) is different from that by large Sr(2+). Nevertheless, in both cases, the beta-TCP stabilization is realized by an improvement of the environment of the Ca4 site unusually face-coordinated to a PO(4) tetrahedron. The substitution of a Mg atom in the Ca5 site allows considerable improvement of the bond valence sum of the unusual Ca4 polyhedron. The temperatures of calcination combined with the amount of Mg atoms introduced allow monitoring of the phase composition of the BCP ceramics as well as their microstructural properties. The bioactivity properties of the BCP samples are improved by the presence of Mg atoms in the structure of the beta-TCP phase. The mechanism of improvement is mainly attributed to an accelerated kinetic of precipitation of a calcium phosphate layer at the surface comprising HAp and/or beta-TCP phases.
溶胶-凝胶化学已被用于制备未掺杂和 Mg 取代的双相磷酸钙（BCP）陶瓷，由羟基磷灰石（HAp）和密磷钙石（β-TCP）相组成。不同系列的样品已通过不同的 Mg 掺杂水平（取代 Ca 原子的 0 至 5 个原子%）和不同的煅烧温度（500 至 1100°C）合成。所有的粉末样品都通过 Rietveld 精修进行了系统处理，以提取定量相分析、结构和微观结构参数、定位 Mg 晶体位置并优化 Mg 取代相的组成。由于形成了少量的相，如 Ca2P2O7、CaO、MgO 和 CaCO3，以及肯定的非晶相，因此 HAp 和β-TCP 的重量比的温度依赖性不是单调的。另一方面，已经证明并解释了 Mg 对β-TCP 相的稳定作用。少量 Mg2+的稳定机制与大量 Sr2+不同。然而，在这两种情况下，β-TCP 的稳定都是通过改善异常面配位到 PO4四面体的 Ca4 位的环境来实现的。Mg 原子在 Ca5 位的取代允许异常 Ca4 多面体的键价和的相当大的提高。煅烧温度与引入的 Mg 原子数量的结合允许监测 BCP 陶瓷的相组成以及它们的微观结构特性。结构中存在 Mg 原子提高了 BCP 样品的生物活性。改善的机制主要归因于在包含 HAp 和/或β-TCP 相的表面上沉淀磷酸钙层的动力学的加速。
