In-Situ Processing of Superconducting MgB2-Metal Composites

该提议是关于使用反应合成来处理硼化镁（MgB 2），该反应合成包括用熔融镁对B纤维进行压力渗透以在Mg基体中形成连续的MgB 2相。一个主要的目标是在超过25 K的温度下实现超导应用。加工温度，硼的体积分数，尺寸和形状对所得的微观结构的影响将使用各种表征技术，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进行研究。将评估反应的MgB 2纤维和MgB 2-金属复合材料的机械和超导性能，并与微观结构相关联。实验研究之后将首先使用一维模型来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来预测复合材料。该项目的最终目标是从固体B和液体Mg中合成MgB 2，以制造连续长度的超导金属-MgB 2复合线。该研究强调开发一种工艺，用于制造临界温度为39 K的连续，低成本的金属-MgB 2复合超导线材，通过对合成所涉及的材料科学问题的基于科学的预测性理解，在25-30 K温度下，在无氦低温条件下，与目前由液氦冷却的Nb 3Sn型导线相比，冷却将导致成本显着下降，液氦是一种昂贵的、不可再生的资源。可能的应用包括用于能量存储装置的超导磁体、悬浮系统（用于火车）、马达、用于电力传输的电线和超导量子干涉装置（SQUID）系统。这项研究为本科生和研究生以及高中教师提供了机会，通过推广计划获得涉及材料加工和表征技术的实验室经验。计划包括建立一个关于二硼化镁合成的网站，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.