Design of novel ceramics with crystalline-oriented layers produced by electrophoretic deposition under a high magnetic field

陶瓷的各向异性设计引起了人们的关注，因为它们具有更好的电学、机械和其他性能。织构结构陶瓷的制备方法主要有热成形、模板化晶粒生长等。然而，在使用这些技术时，形状和方向方向受到限制。另一方面，我们已经报道，即使对于氧化铝、二氧化钛、氧化锌等抗磁性陶瓷，也可以通过在强磁场中注浆浇注然后加热来控制织构的发展。将稳定的胶体悬浮液置于强磁场中，利用电泳法沉积(EPD)成型织构陶瓷。在本研究中，我们证明了在强磁场中，EPD可以制备出不同取向层的层状陶瓷。利用超声均质机和磁力搅拌器将氧化铝粉末分散在悬浮液中。将悬浮液置于超导磁体中，然后在悬浮液中施加10T的强磁场，使每个颗粒受到各向异性磁化率的磁矩旋转。改变了电场相对于磁场的方向，以控制主导晶面。烧结温度为1873K，在无磁场的空气中烧结2小时。我们在以前的报道中证实了具有六方晶胞的氧化铝的c轴平行于磁场的方向。在10T电火花放电过程中，通过交替改变磁场和电场方向的夹角，制备了具有不同晶向的复合材料。层状复合材料的弯曲强度取决于多层微结构的方向。裂纹沿曲折路径弯曲扩展。裂纹路径沿各层中的取向方向。

Anisotropic designs of ceramics have attracted attention, because of their improved electrical, mechanical and other properties. Texture structured ceramics have been produced by hot forming, Templated Grain Growth (TGG) and so on. However, shape and orientation direction are limited, when using these techniques. On the other hand, we have reported that development of texture can be controlled by slip casting in a strong magnetic field followed by heating even for diamagnetic ceramics such as alumina, titania, zinc oxide and so on. Electrophoretic deposition (EPD) is also applied to shaping textured ceramics from stable colloidal suspension which is placed in a strong magnetic field. We demonstrate in this study that laminar ceramics with different crystalline-oriented layer are produced by EPD in a strong magnetic field. The alumina powder was dispersed in a suspension by using an ultrasonic homogenizer and a magnetic stirrer. The suspension was placed in a superconducting magnet, and then a strong magnetic field of 10T was applied to the suspension to rotate each particle by a magnetic torque attributed to the anisotropic susceptibility. The direction of the electric field relative to the magnetic field was altered to control the dominant crystal faces. The sintering was conducted at 1873K for 2h in air without a magnetic field. We confirmed in our previous reports that c-axis of alumina with the hexagonal unit cell was parallel to the direction of magnetic field. The composite with different crystalline-oriented layer was fabricated by alternately changing the angle between the directions of the magnetic and electric fields layer by layer during EPD in 10T. Bending strength of laminar composite depended on the direction of multilayered microstructure. Crack was propagated by bending in a zig-zag path. The crack path was along the direction of orientation in each layer.