超音速等离子喷涂制备非对称型La0.6Sr0.4Co0.2Fe0.8O3-δ透氧膜的性能

Properties of asymmetrical La0.6Sr0.4Co0.2Fe0.8O3-δ oxygen transport membrane prepared by supersonic air-gas plasma spraying

采用超音速等离子喷涂方法制备出了La0.6Sr0.4Co0.2Fe0.8O3-δ(LSCF-6428)非对称型透氧膜。利用双聚焦离子束、扫描电镜、透射电镜、X射线衍射仪等手段观测膜层微观结构和物相成分,重点考察膜层高温结构稳定性和抗CO2腐蚀性能。采用四探针法测电导率比较SAPS膜和传统烧结膜的电子传导性能。结果表明,SAPS膜结构致密程度较高,膜层内部富含纳米晶粒,并呈现“微纳晶-纳米晶-超细纳米晶”顺序叠加结构。膜经历850℃,30次热循环测试和25 h持续加热测试后仍维持较高的致密度,表现出较好的结构稳定性。膜层在静态CO2气氛下,500℃时即开始相分解,且随着温度升高,相分解加速,到900℃时相分解快速完成并终止。相比之下,膜层在950℃,CO2吹扫气氛下相分解速率明显减慢,在经历2h加热后仅发生轻微分解。四探针法测得SAPS膜常温电导率达到0. 28 (Ω·cm)^-1,高出烧结膜一个数量级。进一步研究表明,SAPS膜晶格发生膨胀,引发膜层内部极化子尺寸增大,有助于内部电子的迁移。

Asymmetric La0.6Sr0.4Co0.2Fe0.8O3-δ( LSCF-6428) oxygen transport membrane was prepared by supersonic air-gas plasma spraying( SAPS).Microstructure,composition,thermal structural stability and CO2 corrosion resistance of the membrane were observed and analyzed by means of double focusing ion beam( FIB),scanning electron microscopy( SEM),transmission electron microscopy( TEM) and X-ray diffraction( XRD).The electronic conductivity of the SAPS membrane was compared with that of traditional sintered membrane by four-point probe method.The results show that the SAPS membrane has high density,and the membrane is rich in nanoparticles, and presents the sequence superposition structure of "micro-nanocrystals-nanocystals-ultra-fine nanocrystals ".The membrane maintained a high density after 30 times thermal cycle tests and 25 h continuous heating tests at 850 ℃,showing good thermal structural stability.The phase decomposition of the membrane begins at 500 ℃ in static CO2 atmosphere,and the phase decomposition accelerates with the increase of temperature,and the phase decomposition is completed and terminated rapidly at 900 ℃.In contrast,at950 ℃,the phase decomposition rate of the membrane is obviously slowed down in sweeping CO2 atmosphere,and only slightly decomposed after heating for 2 h.The conductivity of the SAPS membrane measured by four-point probe method at room temperature is0.28(Ω·cm)^-1,which is one order of magnitude higher than that of sintered membrane.Further studies show that the lattice expansion of the SAPS membrane leads to the increase of polaron size in the film layer,which is helpful to the migration of internal electrons.