Effects of bridging fibers on the evolution of lamellar architecture during H2/H2O redox cycling of Fe-foams
Effects of bridging fibers on the evolution of lamellar architecture during H2/H2O redox cycling of Fe-foams
复制标题
桥接纤维对泡沫铁 H2/H2O 氧化还原循环过程中层状结构演化的影响
DOI：
10.1016/j.actamat.2022.118543
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发表时间：
2023
期刊：
影响因子：
9.4
通讯作者：
Dunand, David
中科院分区：
文献类型：
--
作者：
Pennell, Samuel;Dunand, David
本文研究了在800 °C下，Fe/Fe_3O_4氧化还原循环通过循环H_2/H_2O暴露在具有15vol%纤维的层状Fe泡沫中的情况。将纤维整合在泡沫中以通过机械支撑相邻的薄片来减轻循环期间的致密化，从而防止接触点处的屈曲和烧结。检查三种纤维类型：短（0.1 mm）和长（1-2 mm）不锈钢纤维，以及长氧化锆纤维。长纤维桥接层片，并通过增加初始层间孔隙率（从85%）对结构产生显著影响< 60 to >，同时在初始还原和烧结期间泡沫收缩率相应降低（从> 80%至< 55%体积损失）。虽然与无纤维泡沫相比性能提高，但纤维对损坏的有效性随着循环而降低：在10次氧化还原循环后，具有长纤维的泡沫的孔隙率福尔斯从85%下降到50%。一种新的降解机制被确定：纤维吞噬。这种机制发生在连续的氧化还原循环中，因为来自薄片的材料周期性地从纤维中吞没（作为Fe 3 O 4）和退出（作为Fe），在每个循环之后从薄片到纤维的净运输。这种循环粗化机制将泡沫结构从桥接层状（具有均匀分布的孔隙率）改变为混合层状/纤维状（具有不均匀分布的孔隙率）。
Fe/Fe3O4redox cyclingviacyclic H2/H2O exposure at 800 °C is studied in lamellar Fe foams with 15 vol% fibers, created by freeze-casting. Fibers were integrated in the foams to mitigate densification during cycling by mechanically supporting neighboring lamellae, thus preventing buckling and sintering at contact points. Three fiber types are examined: short (0.1 mm) and long (1–2 mm) stainless-steel fibers, and long zirconia fibers. Long fibers bridge lamellae and have a marked effect on the architecture by increasing the initial interlamellar porosity (from < 60 to > 85%), with a corresponding decrease in foam shrinkage during initial reduction and sintering (from > 80 to < 55% volumetric loss). Though performance improves as compared to fiber-free foams, fiber effectiveness against damage decreases with cycling: after 10 redox cycles, porosity falls from 85 to 50% for foams with long fibers. One novel degradation mechanism is identified: fiber engulfment. This mechanism occurs over successive redox cycles, as material from the lamellae cyclically engulfs (as Fe3O4) and withdraws (as Fe) from the fibers, with a net transport from lamellae to fibers after each cycle. This cyclic coarsening mechanism alters foam architecture from bridged-lamellar (with evenly distributed porosity) to mixed lamellar/fibrous (with unevenly distributed porosity).