SOFC不锈钢连接体用新型NiO/NiFe2O4复合涂层的制备及性能研究

The increase in electric resistance due to the Cr2O3 incessant growth as well as the cathode Cr-poisoning due to the evaporation of Cr2O3 limit the application of ferritic stainless steel as solid oxide fuel cell(SOFC) metallic interconnect. In order to solve problems above, it will be an effective method to deposit electrically conductive coating with ability to block Cr outward migration and to suppress thickening of Cr2O3. Based on the super ability to supress Cr migration and high electrical conductivity of NiO as well as the excellent capability to block O inward diffusion and good electrical conductivity of NiFe2O4, NiO/NiFe2O4 composite coating will be prepared on the steel. Columnar nanocrystalline Ni/NiFe2 composite coatings will be deposited on the ferritic stainless steel SUS 430 by magnetron sputtering, followed by the thermally converting to NiO/NiFe2O4. The effects of composition and thickness of Ni/NiFe2 composite coating on the compostion,structure and properties of surface scale formed on the coated steel will be investigated to reveal the formation mechanism and evolvement of the surface scale. Moreover, NiO/NiFe2 composite coating will be deposited on the steel and the oxidation behavior of the coated steel will be investigated to elucidate the effect mechanism of NiO. This project is expected to be greatly significant to develop and apply coatings for SOFC interconnects.

铁素体不锈钢用作固体氧化物燃料电池(SOFC)连接体材料时，需要解决其表面Cr2O3膜不断生长引起的电阻增加和Cr挥发导致的阴极中毒问题。表面施加导电、且能抑制Cr向外迁移和Cr2O3膜增厚的涂层将是一种有效的解决途径。鉴于NiO具有优异的阻止Cr迁移能力和较高的电导率，以及NiFe2O4尖晶石具有良好的导电性和抑制氧迁移能力，本项目拟采用磁控溅射技术在SUS 430铁素体不锈钢表面沉积柱状纳米晶结构的Ni/NiFe2金属复合涂层，然后经热暴露制备NiO/NiFe2O4氧化物复合涂层。研究Ni/NiFe2涂层成分和厚度对涂覆不锈钢表面膜成分、结构和性能的影响，揭示表面膜形成机制和演化过程。其次，研究涂覆NiO/NiFe2复合层不锈钢的高温氧化行为，澄清NiO的作用机制。本研究对于推动SOFC不锈钢连接体表面涂层的发展与应用具有积极意义。

铁素体不锈钢用作固体氧化物燃料电池(SOFC)连接体材料时，需要解决其表面Cr2O3膜不断生长引起的电阻增加和Cr挥发导致的阴极中毒问题。表面施加导电、且能抑制Cr向外迁移和Cr2O3膜增厚的涂层将是一种有效的解决途径。鉴于NiO具有优异的阻止Cr迁移能力和较高的电导率，以及NiFe2O4尖晶石具有良好的导电性和抑制氧迁移能力，本项目采用磁控溅射技术在SUS 430铁素体不锈钢表面沉积柱状纳米晶结构的Ni/NiFe2金属复合涂层（Ni层的厚度不同），涂覆不锈钢在800℃空气中热暴露转化为Cr2O3/NiO/NiFe2O4氧化物涂层。结果表明，增加Ni层厚度，其转化的较厚的NiO层更有利于抑制Cr的外扩散。同时发现，涂覆不锈钢氧化过程中，Ni会向不锈钢基体内扩散，导致NiFe相生成，不利于表面膜的粘附性提高。为此，先将不锈钢在800℃空气中预氧化50h，使其表面预先生成Cr2O3层，然后再溅射沉积Ni/NiFe2涂层，发现预先生成的Cr2O3层完全抑制了氧化过程中Ni的内扩散，氧化后Ni/NiFe2涂层完全转化为NiO/NiFe2O4复合氧化物层，有效抑制了Cr外迁移，减少了Cr挥发，降低了Cr2O3层的生长速率，提高了表面膜的电性能。此外，在不锈钢预氧化之前，将CeO2电泳沉积在不锈钢表面，发现CeO2进一步改善了了表面膜的结合力。本研究对于推动SOFC不锈钢连接体表面涂层的发展与应用具有积极意义。