Evolution of lamellar architecture and microstructure during redox cycling of Fe-Co and Fe-Cu foams
Evolution of lamellar architecture and microstructure during redox cycling of Fe-Co and Fe-Cu foams
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Fe-Co 和 Fe-Cu 泡沫氧化还原循环过程中层状结构和微观结构的演变
DOI：
10.1016/j.jallcom.2022.165606
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发表时间：
2022
影响因子：
6.2
通讯作者：
Dunand, David C.
中科院分区：
文献类型：
--
作者：
Pennell, Samuel M.;Mack, Jacob B.;Dunand, David C.
研究了 Fe 与 25 at% Co 或 30 at% Cu 合金化在冷冻铸造层状泡沫中的影响，该泡沫在 800 ℃ 富含 H2 和 H2O 的气氛下进行氧化还原循环，与金属-空气电池相关。在非合金铁泡沫中，氧化还原循环会导致片层内不可逆的柯肯达尔孔隙度增长，导致片层结构断裂和屈曲，进而导致泡沫在几个循环后致密化。相比之下，Fe-25Co 片层在氧化时会形成纯 Co 核和 Fe3O4 壳，从而减少屈曲和柯肯德尔孔的生长，从而减缓层状泡沫的烧结和致密化。 Fe3O4 还原后，片层的富 Fe 壳和富 Co 核通过扩散到原始单相 Fe-25Co 合金中而重新均匀化，在完整的氧化还原循环中实现可逆的微观结构。 10 个循环后，平均通道孔隙率（片层之间）仅小幅下降（从 62% 降至 46%），片层中的柯肯德尔孔粗化程度最小，这与 Fe-25Co 泡沫的强烧结阻力一致。 Fe-30Cu 泡沫在氧化后也呈现出具有 Cu 核和 Fe3O4 壳结构的片层，因为 Cu 与 Co 一样，在蒸汽下不会氧化。然而，Cu 在 Fe 中溶解度的缺乏阻碍了 Fe3O4 还原后的再均质化，因此所得的 Cu 核/Fe 壳片层在随后的氧化还原循环中经历了严重的烧结和致密化，仅 5 个循环后通道孔隙率就从 61% 降低到 9%。对于这两个系统，氧化还原循环过程中的操作射线衍射表明，与纯泡沫铁相比，与钴不同，铜的氧化速率加倍。
The effects of alloying Fe with 25 at% Co or 30 at% Cu are studied in freeze-cast lamellar foams subjected to redox cycling under H2- and H2O-rich atmospheres at 800 ºC, relevant to metal-air batteries. In unalloyed Fe foams, redox cycling causes irreversible Kirkendall porosity growth within lamellae, leading to fracture and buckling in the lamellar architecture which in turn leads to foam densification after a few cycles. By contrast, Fe-25Co lamellae develop, upon oxidation, a pure Co core and a Fe3O4shell which decreases buckling and Kirkendall pore growth, thus slowing sintering and densification of the lamellar foams. After Fe3O4reduction, the Fe-rich shells and Co-rich cores of the lamellae re-homogenize by diffusion to the original single-phase Fe-25Co alloy, achieving a reversible microstructure upon a full redox cycle. After 10 cycles, average channel porosity (between lamellae) undergoes only a small decrease (from 62 % to 46 %), with minimal Kirkendall pore coarsening in the lamellae, consistent with strong sintering resistance in the Fe-25Co foams. The Fe-30Cu foams also display lamellae with Cu core and a Fe3O4shell structure after oxidation, since Cu, like Co, does not oxidize under steam. However, the lack of solubility of Cu in Fe prevents re-homogenization after Fe3O4reduction, so the resulting Cu-core / Fe-shell lamellae undergo severe sintering and densification upon subsequent redox cycling, with channel porosity reducing from 61 % to 9 % after just 5 cycles. For both systems,operandox-ray diffraction during redox cycling reveals that Cu, unlike Co, doubles the Fe oxidation rate, as compared to pure Fe foams.