Elucidation of electrophoretic deposition behavior of particles suspended in aqueous media and characterization of highly structure-ordered ceramics

研究了钯电极对陶瓷水悬浮液的电泳沉积特性。钯电极抑制阴极上产生的氢泡干扰了颗粒的电泳，抑制了颗粒的沉积。表面带电粒子的表观输运数很低，并不是溶剂中的主要载体。在恒流模式下的EPD中，电极之间的外加电压随溶剂的pH值或离子电导率而变化。pH越低，沉积速率越低，颗粒堆积率越高。对EPD法制备的水悬浮液氧化锆/氧化铝复合材料的力学性能和电学性能进行了表征。由于氧化铝层内存在较高的残余压应力，导致复合材料的裂纹发生挠曲。3Y-TZP /氧化铝层状复合材料在与氧化铝层平行方向和垂直方向表现出3Y-TZP的电学性能。电导率测量能很好地反映复合材料的层状结构。结果表明，EPD非常适合于制备具有强结合界面的层状复合材料。EPD还尝试了在强磁场中使用单晶氧化铝颗粒的脱絮悬浮液制备晶体纹理氧化铝陶瓷。在EPD过程中，可以通过改变矢量B和E之间的夹角（ψ B-E）来控制织构陶瓷中的晶体取向。XRD数据估计的平均取向角与ψ B-E角相当一致。复合材料的横截面显微结构清晰地显示了层间界面的结晶织构变化。结果表明，强磁场下的EPD是一种很有前途的制备晶体织构陶瓷的工艺方法。

Electrophoretic deposition characteristics of ceramic aqueous suspensions were studied using palladium electrodes to suppress the hydrogen bubble generation at a cathode which disturbed the electrophoresis of the particles and suppress their deposition. The apparent transport number of the surface-charged particles was very low and they were not dominant carrier species in the solvent. In the EPD at a constant current mode, applied voltage between the electrodes varied with the pH of the solvent or the ion conductivity. Lower pH gave lower deposition rate but higher particle packing.Mechanical and electrical properties of the zirconia/alumina laminate composites fabricated by EPD from aqueous suspensions were characterized. Crack deflection within the alumina layers of the laminate composites was observed because of high compressive residual stress in the alumina layers. The 3Y TZP/alumina laminate composite showed the electrical properties of 3Y-TZP in the parallel direction to the alumina layers and those of alumina in the perpendicular direction. Electrical conductivity measurement well reflected the laminar structure of the laminate composite. It was demonstrated that EPD was well suited to produce layered composites with strongly bonded interfaces.The fabrication of crystalline-textured alumina ceramics were also attempted by EPD in a strong magnetic field using a deflocculated suspension of single crystalline alumina particles. The crystalline orientation in the textured ceramics could be controlled by varying the angle between the vectors B and E (ψ B-E) during EPD. Average orientation angle estimated from the XRD data was fairly consistent with the angle ψ B-E. The cross sectional microstructures of the laminate composites clearly showed the changes in crystalline texture at the interfaces between the layers. It was demonstrated that the EPD in a strong magnetic field was a promising processing technique for making crystalline textured ceramics.