Elastocaloric TiNi-based Films and Devices

该提案代表了联合项目“弹性热Ti-Ni基薄膜和器件”的更新，旨在使用基于ti的形状记忆薄膜进行固态冷却。在第一个资助期内，我们证明了SMA薄膜器件显示出高达-16 K的大温度变化，高于1 Hz的高循环频率以及超高的抗疲劳性（bbb1000万次循环）。这些特性将在利用薄膜和MEMS技术的潜力的创新冷却设备中得到进一步的探索。通过关注沉淀、奥氏体/马氏体晶体相容性和晶粒尺寸的影响，研究了长期稳定性的潜在机制（E. Quandt）。然后，通过研究弹性热效应尺寸和效率，将结果转移到其他材料系统，以确定适合小规模弹性热冷却应用的材料。演示器开发的两种方法是基于固体/固体传热或液体介质中的传热（M. Kohl）。通过调整接触面的形状和力，以及研究微/纳米加工对导热层和表面形貌的影响，固体/固体传热将得到改善。将研究基于再生的弹性热装置在液体介质中的传热。考虑SMA薄膜器件及其环境的热-机械耦合，在器件层面进行了有限元仿真。演示系统（M. Kohl和E. Quandt）将制造和评估冷却功率和长期运行。微冷却应用的潜力将在芯片实验室系统的情况下进行评估。

This proposal represents the renewal of the joint project 'Elastocaloric Ti-Ni based Films and Devices' aiming at solid-state cooling using TiNi-based shape memory films. During the first funding period we demonstrate that SMA film devices show large temperature changes up to -16 K, high cycling frequencies faster than 1 Hz as well as ultra-high fatigue resistance (> 10 million cycles). These properties will be further explored in innovative cooling devices using the potential of thin film and MEMS technology. The underlying mechanisms for long term stability are investigated by focusing on the influence of precipitates, austenite/martensite crystallographic compatibility and grain size (E. Quandt). The results are then transferred to other material systems by investigating elastocaloric effect size and efficiency to identify well suited materials for small-scale elastocaloric cooling applications. Two approaches in demonstrator development are pursued based either on solid/solid heat transfer or on heat transfer in a liquid medium (M. Kohl). Solid/solid heat transfer will be improved by adapting the shape and force of contacting surfaces as well as by investigating the influence of thermally conductive layers and surface topography due to micro/nano-machining. Heat transfer in a liquid medium will be investigated for a regeneration-based elastocaloric device. Finite element simulations are performed on the device level taking into account the thermo-mechanical coupling of SMA film device and its environment. Demonstrator systems (M. Kohl and E. Quandt) will be fabricated and evaluated with respect to cooling power and long-term operation. The potential for microcooling applications will be assessed for the case of a lab-on-chip system.