Preparation of Multi-layered Ceramic Particles

陶瓷颗粒的微观结构或表面形态取决于制备过程和条件，因此它们的性能也相应地变化。利用这种柔性，可以控制颗粒的微结构并制备具有多层或定制微结构的陶瓷颗粒。本研究旨在阐明超声-喷雾热分解法制备的陶瓷颗粒的微观结构与实验条件的关系。对于不含添加剂（甘油）的溶液中的颗粒，表面是光滑的。较大的颗粒是中空的，具有厚壳，而中等尺寸的颗粒是致密的。以乳酸钙、醋酸钙、磷酸二氢铵为原料，EDTA为螯合剂，采用超声喷雾热分解法制备了羟基磷灰石（HAP）颗粒。颗粒的表面形貌取决于实验条件，而观察到的粗糙表面的煅烧良好的颗粒。采用超声喷雾热分解法制备了HAP/赤铁矿（摩尔比为1/0.5 ~ 1/9）复合粒子。平均直径范围为0.2 - 0.6 μ m。随着HAP含量的增加，颗粒的表面会出现褶皱或凹坑，而赤铁矿含量越高，颗粒的表面越光滑。对于较大的颗粒（>O），证实了壳-核型双层结构。直径8 μ m）。这种层状结构是通过Ca-EDTA螯合键断裂引发HAP在液滴表面沉淀而形成的。

The microstructures or surface morphology of ceramic particles depend on the preparation procedure and conditions, and thus their properties vary, accordingly. With utilizing such flexibility one can control the microstructure of the particulate and prepare ceramic particles which have a multi-layered or tailored microstructure. This study aims to clarify the dependence of the microstructure of of the ceramic particles through ultrasonic-spray pyrolysis on the experimental conditions.Hematite particles were first prepared by ultrasonic spraying aqueous solutions ferric nitrate. The surface was smooth for the particles out of the solutions without additives (glycerol). Larger particles were hollow with a thick shell, while medium sized particles were dense. The solutions with the additive yielded hollow particles with a thin shell, and dimples were observed on the shell which were caused by the release of decomposed gas out of the particles.Hydroxyapatite (HAP) Particles were prepared by ultrasonic spray-pyrolysis of aqueous solutions of calcium lactate or acetate, ammonium dihydrogen orthophosphate with EDTA as the chelating agent. The surface morphology of the particles depended on the experimental conditions while the rough surface was observed for the well-calcined particles. The particles were about 0.5mum in diameter.With those aqueous solutions HAP-hematite composite particles were prepared through the ultrasonic spray pyrolysis where the molar ratio HAP/hematite was 1/0.5-1/9. The average diameter ranged from 0.2 to 0.6mum. With larger HAP content the surface was wrinkled or dimple-full, while the smooth surface was for the particles with greater hematite contents. A shell-nuclear type double layer structure was confirmed for larger particles (>O. 8mum in diameter). Such layered structure was built by initiating the HAP precipitation on the surface of the droplets due to breakage of Ca-EDTA chelate bonding.