Powder Metallurgical Fabrication of Artificial Tooth Root of Hydroxyapatite/Ti with Bio-mimetic Structure

浆料浸渍法具有良好的形状成形和微观结构控制能力，可用于制备羟基磷灰石/钛仿生材料。两种成分的梯度层根据最佳组合物分布形成，用于在高温处理期间发生的热应力降低，以及用于最佳生物相容性。通过浆料浸渍成功地形成了这种梯度层。从分散介质、分散剂、粘结剂和原粉的性质出发，详细研究了浆料的分散性、沉降性、粘度、流变性和屈服值。研究了低粘度和高粘度浆料以扩大膜厚度控制的可能性。对于低粘度浆料，有必要抑制分散体颗粒的沉降，而对于高粘度浆料，澄清浆料的流动特性对于确定屈服值是重要的，这是精确控制浸涂层厚度所需的。高粘度浆料不发生沉降，用粘度和屈服值控制膜厚比较容易。浸涂层的固结过程，包括干燥和脱脂，遵循传统的粉末冶金技术，特别注意与烧结收缩有关的问题，这是组成分级的特征。在本研究中，优化了工艺条件，以获得良好的梯度层，以获得更好的生物相容性。然而，一般来说，最佳工艺条件取决于待加工物体的材料种类、形状和尺寸，并且在将当前工艺条件应用于实际齿根生产时，需要进行或多或少的实践和技术研究来修改。

Slurry dipping method was employed for the processing of hydroxiapatite/Ti biomimetic materials because of its capability of shape forming and microstructural control. The graded layers of both constituents were formed according to an optimum composition profile for the thermal stress reduction which will occur during high temperature processing, and for the optimum bio compatibility. Such graded layers were successfully formed by slurry dipping. Dispersion, sedimentation, viscosity, rheology, as well as yield value, of the slurries were investigated in detail in connection with properties of dispersion medium, dispersion reagent, binder and raw powders. Low- and high-viscosity slurries were investigated to enlarge a possibility of film thickness control. For the low-viscosity slurry it is necessary to suppress the sedimentation of dispersion particles, while for the high-viscosity slurry it turned out to be important to clarify the flow characteristics of the slurry for the determination of the yield value, which is needed for the precise control of the dip-coated layer thickness. The high-viscosity slurry was free from sedimentation, and the control of the film thickness with viscosity and yield value was rather easier. The consolidation process of the dip-coated layer, including drying and debinding, followed conventional powder metallurgical techniques, with particular attention on an issue pertaining to the sintering shrinkage which is characteristic to composition grading. In the present investigation the process conditions were optimized to get a sound graded layer for a better bio-compatibility. In general, however, the optimum process condition depends on material species, shape and size of the objects to be processed, and in applying the present process conditions to actual tooth root production a modification will be necessary with more or less practical and technical study.