SGER: Superconducting MgB2/Metal Composites

本研究的总体目标是展示和研究由两个共连续相，超导MgB 2和金属Mg组成的超导复合材料的反应合成。待研究的两种途径（反应性液体金属渗透和反应性机械合金化）通过B粉末或纤维与液体或固体Mg的反应产生MgB 2相。反应的动力学和中间相的形成（例如，MgB 4）将通过金相学、使用传统和同步加速器源的X射线衍射以及诸如微探针和西姆斯的表面技术来研究。复合材料的超导和机械性能也将进行评估。使用这两种途径加工的材料将使用金相学进行表征，以确定MgB 2相和其他可能的反应产物的孔隙率、连通性和结构。这些将通过XRD和SXRD以及表面科学技术如微探针和西姆斯（后者对硼高度敏感）进行进一步研究。机械合金化粉末以及渗透或致密化复合材料的密度将通过氦比重计测定。还将测量硬度和压缩机械性能（模量、强度和延展性）。将在环境温度和2-50 K范围内研究电导率。超导性能将用计算机控制的磁强计测量，允许SQUID测量磁化强度的温度依赖性，最高可达55 KG。这是一个关于Mg-MgB 2系统的冶金/材料科学研究的小额资助探索性项目，可能对最终制造用于储能设备，医学成像系统，悬浮装置和粒子加速器其他应用包括用于电力传输和小型SQUID系统的电线。拟议的工作是基础研究，如果成功，可能会提供进一步的研发和这些超导复合材料的最终商业化的动力。

The overall goal of this study is to demonstrate and investigate the reactive synthesis of superconducting composites consisting of two co-continuous phases, superconducting MgB2 and metallic Mg. The two routes to be studied (reactive liquid metal infiltration and reactive mechanical alloying) produce the MgB2 phase by reaction of B powders or fibers with liquid or solid Mg. The kinetics of the reaction and the formation of intermediate phases (e.g., MgB4) will be studied by metallography, x-ray diffraction using both traditional and synchrotron sources and surface techniques such as microprobe and SIMS. Superconducting and mechanical properties of the composites will also be assessed. The materials processed using the two routes will be characterized using metallography to determine porosity, connectivity and architecture of the MgB2 phase and other possible reaction products. These will further be investigated by XRD and SXRD, as well as surface science techniques such as microprobe and SIMS, the latter being highly sensitive to boron. The density of the mechanically alloyed powders as well as the infiltrated or densified composites will be determined by helium pycnometry. The hardness and compressive mechanical properties (modulus, strength and ductility) will also be measured. The electrical conductivity will be studied; both at ambient temperature and in the range of 2-50 K. Superconductivity properties will be measured with a computer-controlled magnetometer allowing SQUID measurements of temperature-dependence of magnetization up to fields of 55KG.This is a small grant exploratory project on the metallurgical/materials science study of the Mg-MgB2 system and may have significant importance in the eventual fabrication of tough, superconducting wires for magnets in energy storage devices, medical imaging systems, levitating devices and particle accelerators. Other applications include wires for power transmission and small SQUID systems. The proposed work is fundamental research and if successful may provide the impetus for further R&D and eventual commercialization of these superconducting composites.