Textured La2NiO4+δ membrane with enhanced oxygen permeability

混合离子-电子导电（MIEC）陶瓷基膜因其氧传输速率而受到广泛关注。钙钛矿基材料往往倾向于在二氧化碳大气中形成碳酸盐。Ruddlesden-Popper型氧化物La2NiO4+δ在工作条件下在二氧化碳气氛中具有较高的化学稳定性，因此用它制备膜是有利的。但与钙钛矿材料相比，氧通量较差。因此，制备高透氧率La2NiO4+δ膜是现代研究的热点。本项目研究了具有增强氧透性的La2NiO4+δ结构膜的合成。为了提高渗氧性能，提出了一种带式铸造模板式晶粒生长方法。由于材料氧通量的各向异性，多晶La2NiO4+δ膜的颗粒排列需要控制。文献中描述了几种各向异性材料的模板化晶粒生长方法，并显示出与单晶相当的材料特性。对于这种方法，大的各向异性模板颗粒分散在细粒度等轴颗粒的基质中。采用溶胶-凝胶法合成了等轴颗粒，采用熔盐通量法合成了各向异性模板颗粒。浆料生产后，得到有纹理的板材。这些有纹理的板在烧结前被堆叠和层压。热处理有利于各向异性颗粒的生长，而不是小基体颗粒。颗粒被煅烧，直到它们相互碰撞，得到各向异性材料。最后对织构La2NiO4+δ膜的氧透性、氧表面交换系数和氧扩散系数进行了测定。

Mixed ionic-electronic conducting (MIEC) ceramic-based membranes gained considerable attention, concerning their oxygen-transporting rates. Perovskite-based materials often tend to form carbonates in carbon dioxide atmospheres. The Ruddlesden-Popper type oxide La2NiO4+δ has the advantage of high chemical stability in carbon dioxide atmosphere at working conditions, thus membranes made of it would be favorable. However, compared to perovskite materials, the oxygen flux is poor. Therefore, the synthesis of La2NiO4+δ membranes with high oxygen permeation rates is a topic of interest in modern research. This project deals with the synthesis of textured La2NiO4+δ membranes with enhanced oxygen permeation. To enhance the oxygen permeation properties, a templated grain growth method by tape casting is proposed. Due to the anisotropy of the oxygen flux of the material, the particle arrangement of polycrystalline La2NiO4+δ membranes needs to be controlled. The templated grain growth method is described for several anisotropic materials in the literature and shows material properties, comparable to single crystals. For this method large anisotropic template particles are dispersed in a matrix of fine-grained, equiaxial particles. The equiaxial particles are synthesized via a sol-gel route and the anisotropic template particles are synthesized via a molten-salt flux method. After the production of the slurry, textured plates are obtained. These textured plates are stacked and laminated before sintering. Through heat treatment the growth of the anisotropic particles is favored over the small matrix particles. The particles are calcined until they impinge on one another and an anisotropic material is obtained. Finally, oxygen permeability, oxygen surface exchange coefficient and oxygen diffusion coefficient of the manufactured, textured La2NiO4+δ membranes are estimated.