中低温下SrCoO3-δ基透氧膜相变抑制策略及稳定化机理研究

Industrialization of mixed-conducting oxygen permeable membrane is hindered due to its high operating temperature (>800 ℃), energy-wasting, difficult sealing and strict requirement of membrane module at present. Although the problems can be overcome at intermediate-low temperature (400-700 ℃), the phase transition leading to degradation of oxygen permeable membrane is hard to be conquered. Among numerous membrane materials, SrCoO3-δ-based membrane with high oxygen permeability was investigated extensively. However, the phase transition of SrCoO3-δ-based materials remains unsolved. Therefore, it will be selected as the objects of study in this research project. In order to explore an effective method of inhibiting phase transition, different types of Al doped SC materials will be synthesized by modulating the doping means. The evolution of crystal structure of membrane materials with unit cell occupied by different positional doping ions will be focus investigated use in-situ neutron diffraction characterization technique and other means. The coefficients of interfacial exchange and bulk diffusion will be monitored by an oxygen permeation model. Meanwhile, several characterization methods and theoretic calculation will be used for clarifying the mechanism of doping ions for the evolution of crystal structure. The exploitation of inhibiting phase transition and investigation of stabilization mechanism are expected to strongly facilitate the developments of mixed conducting membranes used at intermediate-low temperature.

混合导体透氧膜由于操作温度高（>800 ℃），面临能耗大、密封难、膜组件要求高等难题，限制了其工业化进程。虽然中低温（400-700 ℃）条件下上述问题容易克服，但相变导致的透氧膜性能衰减一直是该条件下难以攻克的难题。众多透氧膜材料中，SrCoO3-δ基材料具有较高的氧渗透能力，引起了人们的广泛研究，然而其中低温下相变问题尚未得到有效解决。因此本项目拟以SrCoO3-δ基材料为研究对象，通过调变掺杂工艺，合成不同类型Al掺杂SrCoO3-δ基材料，探究抑制相变的有效策略。同时通过原位中子衍射等表征手段，重点分析中低温氧渗透条件下掺杂后膜材料的结构演变过程，利用氧渗透模型监测界面交换系数与体相氧离子扩散系数随时间的变化关系，并在此基础上，借助多种表征手段与理论计算探究掺杂离子对晶体结构演变的作用机理。相变抑制策略的开发及相结构稳定化机理的深入研究将有力地推动中低温透氧膜技术的发展。

混合导体透氧膜制氧技术具有制氧纯度高，且可与众多化工过程相结合的优点，受到了人们的广泛关注。在众多透氧膜材料中，SrCoO3-δ基材料具有较高的氧渗透能力，引起了人们的广泛研究。然而，当操作温度低于900 °C时，其具有高氧渗透能力的立方钙钛矿结构会向不具备氧渗透能力的六方钙钛矿结构转变，导致透氧量快速衰减。因此，克服SrCoO3-δ基透氧膜相变具有重要的科学意义和实用价值。为了攻克SrCoO3-δ基透氧膜相变的难题，本项目通过调变掺杂工艺，合成了多种元素掺杂的SrCoO3-δ基透氧膜材料，其中组成为SrCoAl0.03O3-δ的膜片可以将具备高氧渗透能力的正交相稳定至室温，实现了850 °C 50 h的稳定运行，0.5 mm 厚的膜片，透氧量高达1.7 mL cm-2 min-1，优于商业应用所要求的透氧量高于1.0 mL cm-2 min-1的标准，具有一定的应用潜力。这种利用具有合适离子尺寸元素掺杂抑制相变的思路可以拓展到其它由氧空位有序化导致相变的体系。