Bond Strengthening and Grain Size Refinement in Superhard Metal Borides

超硬金属硼化物中的键强化和晶粒尺寸细化

• 批准号: 2312942
• 负责人: Richard Kaner
• 金额: $ 64万
• 依托单位: University of California-Los Angeles
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-06-01 至 2026-05-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2312942&HistoricalAwards=false
• 关键词: Bond; Strengthening; Grain; Size; Refinement

Non-technical SummaryThe continuous creation and development of tools through the tuning of materials’ properties has been a cornerstone of much of the development seen in human societies. High mechanical hardness is a very desirable property for materials used in industrial settings for machining and cutting as it dramatically reduces wear and therefore turnover rate of machining tools. The industry standard superhard material is diamond, the hardest material currently known. The issue that arises with diamond, however, is that not only does it have an expensive high pressure, high temperate synthesis, but it is limited in its applications. This is because it is thermally unstable in air and when used to cut iron containing materials, diamond breaks down to form iron carbides. These both result in a high turnover rate for diamond tools, and an inability to be used with common iron containing materials, like steel. Cheaper alternatives such as tungsten carbide (WC) have an easier, low-cost synthesis, but lack the extremely high hardness values of diamond and therefore have high turnover rates and are less effective. With this project, supported by the Solid State and Materials Chemistry program and the Ceramics program, both in NSF’s Division of Materials Research, the principal investigators design and create superhard materials that approach the high hardness seen in diamond, while replicating the low cost, ambient pressure synthesis found in WC. These superhard materials made from boron not only lower the cost of synthesis, but they improve the lifetime of the tools that can be created and therefore, lower the amount of waste generated in industrial machining. Additionally, the metallic nature of these transition metal borides enables the use of high precision cutting and shaping instruments like plasma cutting, which is currently not usable with electrically insulating materials like diamond, which additionally reduces cost and waste in the formation of these tools. Beyond this research, the principal investigators undertake educational outreach in the greater Los Angeles area. This includes developing lessons and experiments for K-12 schools and presenting them to teachers, along with speaking to students in grade school about not just science, but higher education as a whole. Graduate students who work on this project also gain valuable skills through both the research they conduct as well as through the mentorship and outreach programs they participate in alongside their mentors. Technical SummaryHardness is a mechanical property that is defined by a material’s ability to resist irreversible shape change, known as plastic deformation. The hardness of a given material is dependent on several different materials’ properties, but they can overall be grouped into two categories: intrinsic bonding effects and grain boundary effects. These two contributors to hardness are not mutually exclusive and therefore can be optimized separately and combined to dramatically improve the hardness of a material. This project, with support from the Solid State and Materials Chemistry program and the Ceramics program, both in NSF’s Division of Materials Research, uses the described two-pronged approach towards superhard materials design and combines the synthesis of transition metal boride systems with high-pressure studies to obtain information about the internal deformation mechanisms of bulk and nanocrystalline materials. The research groups at UC Los Angeles study how small element doping into the boron sites of the metal borides affects the bonding. Using systems of di- and tetra- borides with varying amounts of carbon in them, the principal investigators investigate the different carbon bonding regimes, and their impact on hardness. Additionally, synthetic routes for the formation of nanostructured metal borides are explored. The principal investigators utilize new synthetic routes to create nanocrystalline forms of known superhard metal borides such as ReB2, WB2 and WB4 to further increase the hardness of these materials by maximizing the number of grain boundaries which can impede plastic deformation. These nanocrystalline materials also allow for new analytical techniques which are not possible for bulk materials such as Rietveld texture analysis. These two approaches to hardening metal borides can then be combined to create nanocrystalline solid solutions which benefit from both the improved bonding effects and grain boundary effects. The broader impacts of the project are multifaceted and include extensive outreach conducted by the principal investigators aimed at grade school children, the training of both graduate and undergraduate students in their Ph.D. studies and undergraduate research opportunities, respectively, and the development of novel superhard materials which have the potential to improve the quality of industrial manufacturing and machining tools.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

非技术摘要通过调整材料性能来不断创造和开发工具一直是人类社会发展的基石。对于工业环境中用于机械加工和切割的材料来说，高机械硬度是非常理想的性能。它极大地减少了加工工具的磨损，从而降低了加工刀具的周转率。行业标准的超硬材料是金刚石，它是目前已知的最硬的材料。然而，金刚石所带来的问题是，它不仅具有昂贵的高压、高温合成材料。 ，但也是有限的这是因为它在空气中热不稳定，并且当用于切割含铁材料时，金刚石会分解形成碳化铁，这都会导致金刚石工具的高周转率，并且无法与普通工具一起使用。碳化钨 (WC) 等含铁材料的合成更容易、成本更低，但缺乏金刚石的极高硬度值，因此周转率较高，且该项目的效果较差。 ，由固态和材料支持NSF 材料研究部的化学项目和陶瓷项目的主要研究人员设计和制造了接近金刚石高硬度的超硬材料，同时复制了由 WC 制成的低成本、常压合成。硼不仅可以降低合成成本，而且可以提高所制造工具的使用寿命，从而减少工业加工中产生的废物量。此外，这些过渡金属硼化物的金属性质可以实现高精度。等离子切割等切割和成型工具目前无法用于金刚石等电绝缘材料，这进一步减少了这些工具形成过程中的成本和浪费。除了这项研究之外，主要研究人员还在大洛杉矶地区开展了教育推广活动。这包括为 K-12 学校开发课程和实验并向教师展示，以及与小学学生谈论科学，以及整个高等教育，参与该项目的研究生也可以通过这两个方面获得宝贵的技能。他们进行的研究以及通过指导和他们与导师一起参与的外展项目。 技术摘要硬度是一种机械特性，由材料抵抗不可逆形状变化（称为塑性变形）的能力定义。给定材料的硬度取决于几种不同材料的特性。总体上可以分为两类：内在结合效应和晶界效应，这两个影响硬度的因素并不相互排斥，因此可以在 Solid 的支持下单独优化并组合起来，以显着提高材料的硬度。状态NSF 材料研究部的材料化学项目和陶瓷项目采用上述双管齐下的方法进行超硬材料设计，并将过渡金属硼化物系统的合成与高压研究相结合，以获得有关内部变形机制的信息加州大学洛杉矶分校的研究小组利用二硼化物和四硼化物系统研究了金属硼化物硼位点的小元素掺杂对键合的影响。此外，主要研究人员还探索了形成纳米结构金属硼化物的合成途径，以创造已知的纳米晶体形式。 ReB2、WB2 和 WB4 等超硬金属硼化物可通过最大限度地增加阻碍塑性变形的晶界数量来进一步提高这些材料的硬度。对于块状材料（例如 Rietveld 织构分析）而言不可能的新分析技术可以结合起来，以创建纳米晶固溶体，从而受益于改进的粘合效应和晶界效应。该项目是多方面的，包括主要研究人员针对小学生进行的广泛推广，分别为研究生和本科生提供博士研究和本科生研究机会，以及开发新型超硬材料。的潜力提高工业制造和加工工具的质量。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。