Shape‐memory ceramics offer promise for applications like actuation and energy damping, due to their unique properties of high specific strength, high ductility, light weight and inertness in harsh environments. To date, shape‐memory behavior in ceramics is limited to micro/submicro‐scale pillars and particles to circumvent the longstanding problem of transformation‐induced fracture which occurs readily in bulk polycrystalline specimens. The challenge, therefore, lies in the realization of shape‐memory properties in bulk ceramics, which requires careful design of three‐dimensional structures that locally mimic pillar structures. In this work, it is demonstrated that with a gradient‐controlled freeze‐casting approach, honeycomb‐like cellular structures can be fabricated with thin and directionally aligned walls to facilitate martensitic transformation under compression without fracture. With this approach, robust bulk shape‐memory ceramics have been demonstrated in a highly porous structure with strengths under compressive stresses of 25 MPa and strains up to 7.5%.

中文翻译：

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通过梯度控制冷冻铸造的坚固的蜂窝形状记忆陶瓷

形状记忆陶瓷具有高比强度、高延展性、重量轻和在恶劣环境中惰性的独特特性，为驱动和能量阻尼等应用提供了希望。迄今为止，陶瓷中的形状记忆行为仅限于微/亚微尺度的柱子和颗粒，以规避长期存在的大块多晶样品中容易发生的相变诱导断裂问题。因此，挑战在于在块状陶瓷中实现形状记忆特性，这需要仔细设计局部模仿柱状结构的三维结构。在这项工作中，证明了使用梯度控制的冷冻铸造方法，蜂窝状蜂窝结构可以制造成具有定向排列的薄壁，以促进压缩下的马氏体转变而不会断裂。通过这种方法，已经在高度多孔结构中证明了坚固的块状形状记忆陶瓷，在 25 MPa 的压缩应力和高达 7.5% 的应变下具有强度。