Materials World Network: Microstructural Design for Enhanced Efficiency in Solid State Energy Conversion

美国德州农工大学和中国上海交通大学合作，研究了磁性形状记忆合金（msma）的微观结构设计，以实现高效的能量转换。这些材料中固有的热弹性耦合提供了一种基于收集否则浪费的机械功的相当节能的装置的途径。随着磁性和电子耦合的增加，msma作为多色材料为转化为有用的能量形式提供了许多可能性。最近也有研究表明，热弹性过程可以用于制冷，与目前的技术相比，具有较大的理论效率增益。研究人员实施了一个全面的方案来研究磁-热-机械耦合在msma中。美国团队与中国团队合作，制造具有广泛控制微观结构和取向（单晶，双晶，控制纹理）的材料，并将磁热力学行为表征为与晶粒尺寸，粒径，体积分数，形貌和纹理相关的加工参数和微观结构特征的函数。这与磁性结构及其与微观结构的耦合的详细表征相匹配。总体目标是克服当前材料的缺点，如减少相变滞后，增加韧性，提高驱动应力。一个重要的实际目标是实现基于控制凝固和微观结构设计的廉价msma，从而为能量转换应用提供高效的平台。该研究不仅促进了对多功能合金的基本认识，而且高效的msma可能会给固态冷却领域带来革命性的变化。教育方面的好处包括美国学生可以参加上海交通大学的国际研究活动，上海交通大学是中国领先的材料研究大学之一，以及德克萨斯农工大学和上海交通大学之间建立的联合学位课程。中国研究人员的工作得到了中国国家自然科学基金的支持。

A collaboration between Texas A&M University and Shanghai Jiao Tong University, China, investigates the microstructural design of magnetic shape memory alloys (MSMAs) tailored for highly efficient energy conversion. The thermoelastic coupling inherent in these materials provides a route to considerable energy-saving devices based on harvesting of otherwise wasted mechanical work. With the addition of magnetic and electronic couplings, MSMAs as multicaloric materials offer many possibilities for conversion into useful forms of energy. It has also recently been shown that the thermo-elastic process can be harnessed for refrigeration, with large theoretical efficiency gain as compared to current technology. The researchers implement a comprehensive program to study the magneto-thermo-mechanical coupling in MSMAs. The US team collaborates with the Chinese group to fabricate materials with a wide range of controlled microstructures and orientations (single crystals, bi-crystals, controlled texture) and characterize the magneto-thermo-mechanical behavior as a function of processing parameters and microstructural features related to grain size, particle size, volume fraction, morphology, and texture. This is paired with a detailed characterization of the magnetic structure and its coupling to the microstructure. The overall goal is to overcome current material shortcomings, e.g., reduce the transformation hysteresis, increase the toughness, and improve the actuation stress. An important practical target is to achieve inexpensive MSMAs based on controlled solidification and microstructure design, thus providing a highly efficient platform for energy conversion applications. The research not only advances the fundamental understanding of the multi-functional alloys, but highly efficient MSMAs can potentially revolutionize the field of solid-state cooling. Education benefits include the participation of US students in the international research activities at Shanghai Jiao Tong University, one of the leading materials research universities in China, as well as the establishment of a joint degree program between Texas A&M and Shanghai Jiao Tong universities. The work of the Chinese investigators is supported by the National Natural Science Foundation of China.