Coarsening of dendrites in solution-based freeze-cast ceramic systems
Coarsening of dendrites in solution-based freeze-cast ceramic systems
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DOI：
10.1016/j.actamat.2021.117039
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发表时间：
2021-06-21
期刊：
影响因子：
9.4
通讯作者：
Faber, Katherine T.
中科院分区：
文献类型：
--
作者：
Arai, Noriaki;Stan, Tiberiu;Faber, Katherine T.
冷冻铸造材料的形貌通常通过调节凝固前沿速度和温度梯度来控制和调节。最近，它已被证明，粗化，通常在合金系统中实行的类似，也是有效的形态控制在冷冻铸造材料。然而，基本的粗化机制及其对微观结构演变的影响在很大程度上是未知的。在这项研究中，冷冻预陶瓷聚合物/环己烷溶液粗化在2摄氏度和4摄氏度为5小时，所得的形态进行了表征，使用扫描电子显微镜，压汞孔隙率测定法，和X-射线计算机断层扫描。在粗化过程中，微观结构从树枝状（一次孔和二次孔）演变为蜂窝状（具有平坦壁的大开口通道）。一次孔和二次孔的尺寸均随粗化时间的立方根线性增加，与合金体系中的枝晶粗化一致。其他重要的指标，如一次枝晶间距，枝晶生长的方向性，和粗化的影响上的孔隙陶瓷界面面积的报告。这些发现提供了新的见解粗化的冷冻铸造系统，并可能导致新的途径，微观结构的可定制性。(C)2021 Acta Materialia Inc.由爱思唯尔有限公司出版。保留所有权利。
The morphologies of freeze-cast materials are typically controlled and tuned by adjusting the freezing front velocity and temperature gradient. Recently it has been demonstrated that coarsening, similar to that commonly practiced in alloy systems, is also effective for morphological control in freeze-cast materials. However, the underlying coarsening mechanisms and their effect on microstructure evolution are largely unknown. In this study, frozen preceramic polymer/cyclohexane solutions were coarsened at 2 degrees C and 4 degrees C for up to 5 h, and the resulting morphologies were characterized using scanning electron microscopy, mercury intrusion porosimetry, and X-ray computed tomography. During coarsening the microstructure evolved from dendritic (primary and secondary pores) to honeycomb-like (large open channels with flat walls). The size of both primary and secondary pores increased linearly with the cube root of coarsening time, consistent with dendritic coarsening in alloy systems. Other important metrics such as primary dendrite spacing, dendrite growth directionality, and the effect of coarsening on the pore-ceramic interface area are reported. These findings provide novel insights into coarsening of freeze-cast systems and can lead to new avenues for microstructure tailorability. (C) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.