Li H, Khor K A, Cheang P
School of Mechanical and Production Engineering, Advanced Materials Research Centre (AMRC), Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore.
Biomaterials. 2003 Mar;24(6):949-57. doi: 10.1016/s0142-9612(02)00431-3.
Formation mechanism of hydroxyapatite (HA)/titania (TiO(2)) composite coating deposited by high velocity oxy-fuel (HVOF) thermal spray process was studied, and its structural characterization was conducted and elaborated in this paper. The impact theory was employed to analyze the formation procedure of the HA/titania composite coatings. Results revealed that the crater caused by the impact of entirely unmelted TiO(2) particles on the HA matrix during coating formation was of smaller dimensions than the original size of the reinforcements. It was found that chemical reaction between the mechanically blended HA and TiO(2) powder took place exclusively during the impingement stage, and calcium titanate, CaTiO(3), was one notable by-product. The bonding between the HA matrix and TiO(2) reinforcement might have been achieved predominantly through a chemical bond that resulted from the mutual chemical reactions among the components. Differential scanning calorimetry analyses showed that the chemical reaction between HA and TiO(2) was at approximately 1410 degrees C. The TiO(2) addition was found to exert particular effects on the thermal behavior of HA at elevated temperatures, during both heating and cooling cycles. Transmission electron microscopy observation identified the chemical reaction zone between HA and TiO(2), which revealed an improved splats' interface. The reaction zone demonstrated some influence on the grain size of HA nearby during resolidification of the melted portion. A structural model was proposed to illustrate the location of the different phases in the HA/titania composite coating.
研究了高速氧燃料（HVOF）热喷涂工艺制备羟基磷灰石（HA）/二氧化钛（TiO₂）复合涂层的形成机理，并对其结构特征进行了分析和阐述。采用冲击理论分析了HA/二氧化钛复合涂层的形成过程。结果表明，在涂层形成过程中，完全未熔化的TiO₂颗粒冲击HA基体所形成的坑洼尺寸小于增强体的原始尺寸。发现机械混合的HA和TiO₂粉末之间的化学反应仅在冲击阶段发生，钛酸钙（CaTiO₃）是一种显著的副产物。HA基体与TiO₂增强体之间的结合可能主要通过组分间相互化学反应产生的化学键来实现。差示扫描量热分析表明，HA与TiO₂之间的化学反应温度约为1410℃。发现添加TiO₂对HA在加热和冷却循环的高温下的热行为有特殊影响。透射电子显微镜观察确定了HA与TiO₂之间的化学反应区，显示出改善的扁平颗粒界面。反应区在熔化部分重新凝固期间对附近HA的晶粒尺寸有一定影响。提出了一个结构模型来说明HA/二氧化钛复合涂层中不同相的位置。
