A Systematic Dopant-selection Strategy for Advanced Manufacturing of High Strength Transparent Magnesium Aluminate Spinel

高强度透明镁铝尖晶石先进制造的系统掺杂剂选择策略

• 批准号: 2016279
• 负责人: Masashi Watanabe
• 金额: $ 49.94万
• 依托单位: Lehigh University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-08-01 至 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2016279&HistoricalAwards=false
• 关键词: Systematic; Dopant; selection; Strategy; Advanced

Optically transparent magnesium aluminate spinel (MgAl2O4, MAS) is one of the candidates to use in extreme environments such as spacecraft and military vehicle windows, in which conventional silicate glasses or polymers are not suitable. Currently, the processing of MAS materials with high strength and high transparency requires high costs, which is one of the major limiting factors to prevent the MAS materials from the applications. A promising path for achieving high density without loss of strength and transparency is via modification of grain boundary (GB) structures and chemistry with the addition of ppm-level impurities. These impurities at the GBs can alter the motion of boundaries leading to improved materials strength. The work will develop a system for identifying appropriate dopants to modify GB atomic arrangements for improved mechanical strength and transparency. MAS materials with enhanced strength and sufficient transparency can be produced by chemical additives identified through this work. the results. This approach will provide a new route for manufacturing transparent polycrystalline MAS, applicable for the large-scale manufacturing of polycrystalline MAS and potentially other ceramics needed to maintain the nation’s global competitiveness and enhance national defense. The information and approaches will be disseminated through an annual microscopy school.Four different types of earth-abundant elements will be doped into polycrystalline and controlled bi-crystal MAS materials, instead of rare-earths to alter the GB strength and hence mechanical performance. The dopant selection is based on the following criteria: (A) dopants must be larger cations than the native cations Mg2+ and Al3+ for effective GB segregation, (B) dopants ideally take 3+ state rather than 2+ to occupy both cation sites, and (C) dopants should have higher stability in their oxide forms (i.e. stronger bonding with oxygen anions) than either Al or Mg. If these criteria are proven experimentally, this approach would provide a new strategy for designing GB configuration and chemistry, and hence controlling the GB strength by selecting dopants. The GB structures and chemistry will be quantitatively characterized by advanced electron microscopy together with sophisticated micro-mechanical testing to measure the GB fracture toughness. Based on experimental results, we will establish a concept for identifying appropriate dopants to modify atomic arrangements for improved mechanical strength and transparency. The concept established in this project should be relevant to other ternary or more component ionic compounds such as the perovskites SiTiO3 and LaMnO3 and be applicable to other binary ceramics materials.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.

光学透明的铝酸镁尖晶石（MgAl2O4，MAS）是用于航天器和军用车辆窗户等极端环境的候选材料之一，而传统的硅酸盐玻璃或聚合物在这些环境中目前不适合加工高强度和高强度的MAS材料。高透明度需要高成本，这是阻碍 MAS 材料应用的主要限制因素之一，在不损失强度和透明度的情况下实现高密度的一个有前途的途径是通过改变晶界 (GB) 结构和化学性质。添加 ppm 级杂质可以改变晶界运动，从而提高材料强度。这项工作将开发一种系统，用于识别适当的掺杂剂，以修改晶界原子排列，从而提高 MAS 材料的机械强度和透明度。通过这项工作确定的化学添加剂可以产生强度和足够的透明度，这种方法将为制造透明多晶MAS提供一条新途径，适用于多晶MAS的大规模制造。维持国家全球竞争力和增强国防所需的其他陶瓷将通过年度显微镜学校传播。四种不同类型的地球丰富元素将被掺杂到多晶和受控双晶 MAS 材料中。稀土来改变晶界强度并因此改变机械性能，掺杂剂的选择基于以下标准：(A) 掺杂剂必须是比原生的阳离子更大的阳离子。阳离子 Mg2+ 和 Al3+ 可以实现有效的 GB 偏析，(B) 掺杂剂理想情况下采用 3+ 态而不是 2+ 态来占据两个阳离子位点，并且 (C) 掺杂剂的氧化物形式应具有比其更高的稳定性（即与氧阴离子的结合更强）。如果这些标准得到实验证明，这种方法将为设计晶界结构和化学提供新的策略，从而通过选择掺杂剂来控制晶界强度。化学和化学将通过先进的电子显微镜和复杂的微机械测试来定量表征，以测量 GB 断裂韧性，我们将建立一个概念，用于识别适当的掺杂剂以改变原子排列，以提高机械强度和透明度。该项目中建立的标准应与其他三元或多组分离子化合物（例如钙钛矿 SiTiO3 和 LaMnO3）相关，并适用于其他二元陶瓷材料。该奖项反映了 NSF 的法定使命，并具有通过使用基金会的智力优点和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

EELS Spectrum Imaging of Ca Segregation at Grain Boundaries in Magnesium Aluminate Spinel

镁铝尖晶石晶界处 Ca 偏析的 EELS 光谱成像

• DOI: 10.1093/micmic/ozad067.191
• 发表时间: 2023-07
• 期刊: Microscopy and Microanalysis
• 影响因子: 2.8
• 作者: Campos;Kundu, Animesh;Watanabe, Masashi
• 通讯作者: Watanabe, Masashi

Effect of Ca Doping on the Microstructure and Mechanical Properties of Magnesium Aluminate Spinel

Ca掺杂对镁铝尖晶石微观结构和力学性能的影响

• DOI: 10.1017/s1431927622009886
• 发表时间: 2022-08
• 期刊: Microscopy and Microanalysis
• 影响因子: 2.8
• 作者: Campos;Kundu, Animesh;Watanabe, Masashi
• 通讯作者: Watanabe, Masashi

Spatial resolution in transmission electron microscopy

透射电子显微镜的空间分辨率

• DOI: 10.1016/j.micron.2022.103304
• 发表时间: 2022-09
• 期刊: Micron
• 影响因子: 2.4
• 作者: Egerton, R.F.;Watanabe, M.
• 通讯作者: Watanabe, M.

Evolution in X-ray analysis from micro to atomic scales in aberration-corrected scanning transmission electron microscopes

像差校正扫描透射电子显微镜中 X 射线分析从微观到原子尺度的演变

• DOI: 10.1093/jmicro/dfab026
• 发表时间: 2022-02
• 期刊: Microscopy
• 影响因子: 1.8
• 作者: Watanabe, M;Egerton, R F
• 通讯作者: Egerton, R F