Structure-Property Relationships in Transition-Metal Pnictides Confined to Nanoscale Dimensions

技术总结在美国国家科学基金会固体和材料化学资助的这个项目中，将采取关键步骤，以确定纳米尺度的尺寸限制如何影响复杂程度增加的过渡金属化合物(三元配方)的结构-性质关系。将研究三个系统，它们是基于BROCK集团对相关二元相的先前经验以及对独特的尺寸相关物理性质的期望而选择的：(Mm‘)2P(M，M’=Mn，Fe，Co，Ni)，Mn1-xFexAs和Na1-xFeAs。(MM‘)2P相是已建立合成的二元相的三元衍生物。以这些相为目标的动机是基于这样的期望，即相对于双星，它们将在较高的温度下发生铁磁转变，从而使它们潜在地适合于室温应用(磁制冷、数据存储)。之所以选择Mn1-xFexAs相，是因为它们代表了铁掺杂类似的MNAs纳米颗粒，在这种体系中，体相MNAs的热力学相变在纳米尺度上被抑制。相变现象可望通过掺入铁等化学缺陷来控制，这一点将得到明确的检验。最后，将继续研究Na1-xFeAs，因为这些相将能够绘制一系列新的合成空间，从而能够制备结合离子和共价/金属键的纳米材料。此外，纳米Na1-xFeAs的制备将使尺寸限制对超导转变的影响能够在这类新型材料中得到探索。在项目过程中，研究生和本科生研究人员将发展批判性思维和沟通技能，并将学习包括电子显微镜在内的尖端研究技术。该项目还将通过Go-Girl(获得选择--女孩调查现实生活)外联项目，向底特律地区的初中和高中女孩介绍纳米和材料科学，其中许多是少数族裔。非技术总结当制备的固体的尺寸仅为单个原子(纳米材料)直径的10-1000倍时所获得的独特性质有望给从数据存储到能量转换的广泛技术带来革命性的变化。然而，纳米材料在实际设备中的开发受到一些基本领域的进展的限制，包括制造功能纳米材料的既定方法，以及对在这一关键制度下尺寸变化时性能如何变化的深入理解。这项由美国国家科学基金会固体和材料化学资助的项目将确定尺寸、结构和化学成分如何影响一系列被称为过渡金属化合物的相的磁性或超导性质。在研究过程中，将发现支撑这种长度规模的材料准备的关键因素。在纳米尺度上合成过渡金属多肽的理论基础的发展，可能会对催化、能量转换和储能(电池)等领域产生影响。此外，从本文提出的材料研究中获得的洞察力预计将影响这些相在磁记录、制冷和所谓的“自旋电子器件”中的使用。在项目过程中，研究生和本科生将培养必要的批判性思维和技术技能，以及开发下一代先进技术所需的尖端技术实践经验。该项目还将通过Go-Girl(获得选择--女孩调查现实生活)外联项目，向底特律地区的初中和高中女孩介绍纳米和材料科学，其中许多是少数族裔。该计划致力于解决科学、技术、教育和数学(STEM)领域长期代表性不足的群体，并寻求通过为他们提供积极的STEM体验并为他们(及其父母)提供必要的资源和信息来开发这些未开发的资产，以确保他们从教育系统中获得最大利益。

TECHNICAL SUMMARYIn this NSF Solid State and Materials Chemistry funded project, key steps towards establishing how confinement of dimensions to the nanometer scale impacts structure-property relationships in transition metal pnictides of increased complexity (ternary formulations) will be undertaken. Three systems will be studied, chosen based on the prior experience of the Brock group with related binary phases, and the expectation of unique size-dependent physical properties: (MM')2P (M, M' = Mn, Fe, Co, Ni), Mn1-xFexAs, and Na1-xFeAs. The (MM')2P phases are ternary derivatives of binary phases for which syntheses have been established. The motivation for targeting these phases is based on the expectation that they will have ferromagnetic transitions at elevated temperatures, relative to the binaries, making them potentially suitable for room-temperature applications (magnetic refrigeration, data storage). Mn1-xFexAs phases were chosen because they represent Fe-doped analogs of MnAs nanoparticles, a system wherein thermodynamic phase transitions, characteristic of bulk MnAs phases, are suppressed on the nanoscale. It is expected that phase transformation phenomena can be controlled through incorporation of chemical defects, such as Fe, and this will be explicitly tested. Finally, Na1-xFeAs will be pursued because these phases will enable a new range of synthesis space to be charted, enabling nanomaterials combining ionic and covalent/metallic bonding to be prepared. Moreover, the preparation of nanoscale Na1-xFeAs will enable the effect of size confinement on the superconducting transition to be probed in this novel class of materials. In the course of the project, graduate and undergraduate researchers will develop critical thinking and communication skills, and will learn cutting-edge research techniques, including electron microscopy. The project will also introduce Detroit-area middle and high school girls, many of which are minorities, to nano- and materials science through the GO-GIRL (Gaining Options-Girls Investigate Real Life) outreach project. NON-TECHNICAL SUMMARYThe unique properties attained when solids are prepared with dimensions of just 10-1000 times the diameter of an individual atom (nanomaterials) promise to revolutionize a wide range of technologies from data storage to energy conversion. However, the exploitation of nanomaterials in actual devices is limited by progress in a number of fundamental areas, including established methods for making functional nanomaterials and a developed understanding of how properties change when the size is varied in this critical regime. This NSF Solid State and Materials Chemistry funded project will establish how size, structure, and chemical composition affect the magnetic or superconducting properties of a series of phases called transition metal pnictides. In the course of the research, key factors that underpin material preparation on this lengthscale will be discovered. The development of a rationale for the synthesis of transition metal pnictides on the nanoscale has potential to impact fields such as catalysis, energy conversion, and energy storage (batteries). Moreover, insight gained from the study of materials proposed here is expected to impact use of these phases in magnetic recording, refrigeration, and so-called "spintronic" devices. In the course of the project, graduate and undergraduate students will develop the necessary critical thinking and technical skills, as well as hands-on experience with cutting-edge techniques, for developing the next generation of advanced technologies. The project will also introduce Detroit-area middle and high school girls, many of which are minorities, to nano- and materials science through the GO-GIRL (Gaining Options-Girls Investigate Real Life) outreach project. This program addresses perennially underrepresented groups in Science, Technology, Education, and Math (STEM) fields and seeks to develop these untapped assets by empowering them with positive STEM experiences and by providing them (and their parents) with the resources and information needed to ensure they get the most out of the educational system.