金属支撑固体氧化物燃料电池共烧结特性研究

Study on co-sintering characteristics of metal supported solid oxide fuel cells

  • 摘要: 在考虑电池整体热膨胀及陶瓷蠕变的情况下分析电极层和电解质层的烧结机理,阐明金属支撑固体氧化物燃料电池(MS-SOFC)在不同烧结温度及晶粒尺寸下电极和电解质层微观结构的演变、残余应力的分布及变化规律。通过建立Skorohod-Olevsky Viscous Sintering (SOVS)模型,模拟在不同烧结温度和不同晶粒尺寸下,MS-SOFC的各层和各界面的相对密度、应力的分布和演化,并通过高温烧结实验揭示异种晶粒尺寸结构烧结后微观结构形貌的变化。结果表明,电解质和电极的相对密度、各层的残余应力值和突变幅度受到烧结温度的影响。当燃料电池各层材料初始晶粒尺寸较小时,烧结导致的致密化率非常明显,随着晶粒尺寸逐渐增大,其致密化率相对较小,且电池各层的残余应力值和突变幅度逐渐减小。纳米氧化钇稳定氧化锆(YSZ)电解质层更容易烧结,且比亚微米YSZ电解质层烧结后微观缺陷降低更多。MS-SOFC烧结后,阴极和阳极的径向应力为拉伸应力,电解质的径向应力为压缩应力。轴向应力和剪切应力在拉压应力之间周期性变化。拥有微米晶的电极层能够在烧结后保持较大的孔隙率,而拥有纳米晶的电解质在提高电导率的同时还能够降低其致密化烧结温度。当晶体尺寸为纳米级时,残余应力值和分布对烧结温度很敏感。

     

    Abstract: The sintering mechanism of electrode layer and electrolyte layer was analyzed considering the whole thermal expansion of the battery and the creep of the ceramic. The evolution of the microstructure of the electrode and electrolyte layer and the distribution and change of residual stress of the metal supported solid oxide fuel cell (MS-SOFC) under different sintering temperature and grain size were expounded. The Skorohod-Olevsky Viscous Sintering (SOVS) model was established to simulate the relative density and stress distribution and evolution of different layers and different surfaces of MS-SOFC under different sintering temperatures and different grain sizes. The change of microstructure morphology of dissimilar grain size structure after sintering was revealed by high temperature sintering experiment. The results show that the relative density of electrolyte and electrode, the residual stress value of each layer and the mutation amplitude are affected by sintering temperature. When the initial grain size of each layer of fuel cell material is small, the densification rate caused by sintering is very obvious. With the gradual increase of grain size, the densification rate is relatively small, and the residual stress value and mutation amplitude of each layer of the battery are gradually reduced. Nano-yttrium oxide stabilized zirconia (YSZ) electrolyte layer is easier to sintering, and the micro-defects are reduced more than the micron YSZ electrolyte layer after sintering. After sintering of MS-SOFC, the radial stress of cathode and anode is tensile stress, and the radial stress of electrolyte is compressive stress. Axial stress and shear stress vary periodically between tensile and compressive stress. The electrode layer with micron crystals can maintain large porosity after sintering, while the electrolyte with nanocrystalline can improve the conductivity and reduce the densification sintering temperature. When the crystal size is nanometer, the residual stress value and distribution are sensitive to the sintering temperature.

     

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