Metal Diborides: Investigating the Structure, Processing, and Properties of a New Class of Two-Dimensional Materials

非技术描述：金属硼化物是一类化学成分为MB2的陶瓷材料，其中M可以是许多不同的金属。它们有一个共同的结构，即由金属原子层隔开的堆叠的硼片。这些材料的各种杰出性能的例子包括二硼化镁的超导电性以及二硼化钛和二硼化锆的耐极高温度。金属二硼化物还可用于航天器的防弹装甲和隔热层。然而，传统的制备金属硼化物的方法会产生厚而脆的材料，这些材料没有利用其组成的硼片的柔性、二维(2D)性质。PIS最近开发了一种直接产生大量2D金属二硼化物的方法，该方法由单层到几层原子薄片组成。本项目的重点是详细研究这种新型2D陶瓷的结构、性能、工艺和性能。几层金属二硼化物悬浮在多孔表面或并入聚合物中，测试其改善的机械性能。研究了2D金属硼化物薄膜作为轻质和柔性超导体的潜力。总体而言，这些研究的目的是利用金属二硼化物在使用传统材料加工技术无法实现的应用中的特殊性能，并改进其在传统使用领域的性能。该项目的教育目标是对研究生和本科生进行高级材料研究方面的培训，将研究成果纳入研究生和本科生的PIS跨学科课程，并通过开放参观科学活动和家庭虚拟科学工具包向普通公众推广。技术细节：该项目专注于详细了解使用溶液相加工和微机械切割技术制备的2D金属二硼化物薄板的结构和性能。用像差校正的透射电子显微镜、扫描隧道显微镜、电子能量损失谱和能量色散X射线能谱研究了这些2D材料的原子尺度的结构和组成。正在使用原子力显微镜和拉伸测试设备研究不同长度尺度上的力学测量，从2D金属二硼化物的单个微观薄片到2D金属二硼化物增强的宏观聚合物复合材料。溶液处理的2D金属二硼化镁柔性薄膜正在被研究其潜在的超导行为。因此，这项研究项目为金属二硼化物在只有几个原子层厚的情况下的电子和机械性质提供了新的基础知识。随着人们对2D金属二硼化物陶瓷性能和工艺认识的提高，它们被整合成传统块体陶瓷所不具备的可伸缩和柔韧的形式，并为这些化合物在结构增强聚合物复合材料和可弯曲超导体中的应用开辟了新的领域。

NON-TECHNICAL DESCRIPTION: Metal diborides are a class of ceramic materials with the chemical composition MB2, where M can be many different metals. They have a common structure of stacked sheets of boron separated by layers of metal atoms. Examples of the diverse, outstanding properties of these materials include superconductivity in magnesium diboride and resistance to extremely high temperatures in titanium diboride and zirconium diboride. Metal diborides also find application in ballistic armor and heat shields for spacecraft. However, conventional methods of preparing metal diborides result in thick, brittle materials that do not take advantage of the flexible, two-dimensional (2D) nature of their constituent boron sheets. The PIs recently developed a method to directly generate substantial amounts of 2D metal diborides composed of single- to few-layer atomically thin sheets. This project is focused on studying in detail the structure, properties, processing, and performance of this new class of 2D ceramics. Few-layer metal diborides suspended across porous surfaces or incorporated into polymers are tested for their improved mechanical properties. Thin films of the 2D metal diborides are investigated for their potential as lightweight and flexible superconductors. Overall, these studies aim to exploit the exceptional properties of the metal diborides in applications not possible using conventional materials processing techniques and to improve their performance in their conventional areas of use. The educational goals of this project are the training of graduate and undergraduate students in advanced materials research, incorporation of research results into the PIs' interdisciplinary courses for graduate and undergraduate students, and outreach to students and families in the general public through open house science events and at-home virtual science kits.TECHNICAL DETAILS: This project is focused on understanding in detail the structure and properties of 2D sheets of metal diborides prepared using solution-phase processing and micromechanical cleavage techniques. The structure and composition of these 2D materials are studied down to the atomic scale by aberration corrected transmission electron microscopy, scanning tunneling microscopy, electron energy loss spectroscopy, and energy dispersive X-ray spectroscopy. Mechanical measurements across different length scales, starting from individual microscopic sheets of 2D metal diborides to macroscopic polymer composites reinforced by 2D metal diborides, are being studied using atomic force microscopy and tensile testing equipment. Solution-processed, flexible thin films of the 2D metal diboride MgB2 are being investigated for their potential superconducting behavior. This research project is thus providing new fundamental knowledge of the electronic and mechanical properties of the metal diborides once they are only a few atomic layers thick. The improved understanding of the properties and processing of 2D metal diboride ceramics is facilitating their integration into stretchable and flexible forms unavailable to their conventional bulk counterparts, and yielding new application areas for these compounds in structurally reinforced polymer composites and bendable superconductors.