In-Situ Processing of Superconducting MgB2-Metal Composites

该提案是关于使用反应合成方法处理硼化镁（MgB2），涉及B纤维与熔融镁的压力渗透，以在Mg基体中形成连续的MgB2相。一个主要目标是在超过25K的温度下实现超导应用。加工温度、硼的体积分数、尺寸和形状对所得微观结构的影响将使用各种表征技术进行研究，包括金相、微探针、二次离子质谱、同步加速器x射线断层扫描和透射电子显微镜。反应后的MgB2纤维和MgB2-金属复合材料的力学和超导性能将被评估，并与微观结构相关联。实验研究之后将进行建模工作，首先使用一维模型预测硼纤维的断裂强度和弹性模量，然后使用经典和三相自洽方法预测复合材料。该项目的最终目标是为制造连续长度的超导金属-MgB2复合线，从固体B和液体Mg合成MgB2产生科学基础的理解。该研究强调，通过对这些复合材料的合成、结构和性能所涉及的材料科学问题的科学预测理解，开发一种制造临界温度为39 K的连续、低成本金属- mgb2复合超导线的工艺。与目前使用液氦冷却的nb3sn型超导线相比，在25-30 K下不使用氦冷冷却的复合超导线将显著降低成本，液氦是一种昂贵的不可再生资源。可能的应用包括用于储能装置的超导磁体、悬浮系统（用于火车）、电机、电力传输电线和超导量子干涉装置（SQUID）系统。该研究为本科生、研究生以及高中教师提供了机会，通过拓展项目获得涉及材料加工和表征技术的实验室经验。计划包括创建一个关于MgB2合成的网站，并通过使用先进光子源与阿贡国家实验室合作。

The proposal is on the processing of magnesium boride (MgB2) using reaction synthesis involving pressure infiltration of B fibers with molten magnesium to form a continuous MgB2 phase in an Mg matrix. A major goal is to achieve superconducting applications at temperatures in excess of 25K. The influence of processing temperature, volume fraction of boron, size and shape on the resulting microstructures will be studied using various characterization techniques including metallography, microprobe, secondary ion mass spectroscopy, synchrotron x-ray tomography and transmission electron microscopy. The mechanical and superconducting properties of reacted MgB2 fibers and MgB2-metal composites will be assessed and correlated with the microstructures. Experimental studies will be followed by modeling efforts first using 1-dimensional model to predict fracture strength and elastic modulus of boron fibers followed by classical and three-phase self-consistent methods for composites. The ultimate goal of the project is to generate a science-base understanding of the synthesis of MgB2 from solid B and liquid Mg for the fabrication of continuous lengths of superconducting metal-MgB2 composite wires. The research emphasizes the development of a process for creating continuous, low-cost metal-MgB2 composite superconducting wires with a critical temperature of 39 K, through a science-based, predictive understanding of the materials science issues involved with synthesis, structure and properties of these composites.Operation of the composite superconducting wires at 25-30 K without helium cryo-cooling will result in a significant drop in costs as compared to current Nb3Sn-type wires cooled by liquid helium, which is an expensive, non- renewable resource. Possible applications include superconducting magnets for energy storage devices, levitation systems (for trains), motors, wires for power transmission and superconducting quantum interference device (SQUID) systems. The research provides opportunities for undergraduate and graduate students as well as high school teachers through outreach programs for laboratory experience involving materials processing and characterization techniques. Plans include creation of a website on MgB2 synthesis and collaboration with Argonne National Laboratory through the use of Advanced Photon Source.