Structure and Micro-Fracture Testing of Single Grain Boundaries in Ceramics

陶瓷单晶界的结构和微断裂测试

• 批准号: 1131408
• 负责人: Richard Vinci
• 金额: $ 40万
• 依托单位: Lehigh University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-09-01 至 2014-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1131408&HistoricalAwards=false
• 关键词: Structure; Micro; Fracture; Testing; Single

The research objective of this grant is to elucidate the sub-nanometer structural and chemical characteristics of transparent magnesium aluminate spinel grain boundaries that are responsible for intergranular fracture when LiF is used as a sintering aid. It has long been known that partially-disordered intergranular films (IGFs) at the 1-2 nm scale can have a profound effect on the behavior of ceramic materials, and it is now becoming evident that newly-revealed thinner layers (complexions) can have similar effects on macroscopic behavior. Although conventional High-Resolution TEM studies have not identified residual LiF in fully-processed liquid phase sintered spinel, light elements like Li and F are not detectable by this technique in the quantities typical of many boundary complexions so there is high likelihood that sub-nanometer layers of boundary LiF are, indeed, behind the poor boundary strength. The proposed program will test this proposition in a highly coordinated set of experiments correlating the mechanical properties of doped grain boundaries with their associated grain boundary chemistry and structure. This will be accomplished through the marriage of cutting-edge aberration-corrected Scanning Transmission Electron Microscopy (ac STEM) and newly-developed microscale fracture testing techniques that are suitable for evaluating the local fracture properties of boundaries.The results of this program will inform the development of transparent, fracture-resistant spinel materials for spacecraft windows, sensor domes, armor, and protective goggles and face shields. Although the study of interface complexions is in its early days, the long-term impact of the proposed work is through the contribution of a key element (the link between boundary fracture behavior and complexion) to a developing scientific framework for documenting, understanding and exploiting complexions in ceramic materials. There is great potential to achieve unique combinations of properties in many ceramic (and even metallic) systems by tailoring grain boundary structure and chemistry according to the complexion framework. The development of micro-scale fracture techniques that can be performed using commercially-available instruments will present, for the first time, the opportunity for a large number of people and industries to be directly involved in carrying out quantitative fracture measurements with very small volumes of material. Impact on human development will be primarily through the education and training of the graduate students and undergraduates who will be involved with the project, who will have access to the latest microscopy and microtesting technologies. Impact on the local community will be achieved through continuing participation in outreach activities including ?NanoDays? at the Da Vinci Discovery Center of Science and Technology in Allentown, PA.

该研究的目的是阐明透明镁铝尖晶石晶界的亚纳米结构和化学特性，当LiF用作烧结助剂时，这些晶界是导致晶间断裂的原因。人们早就知道，1-2 nm尺度的部分无序的晶间膜（IGFs）可以对陶瓷材料的行为产生深远的影响，现在越来越明显的是，新发现的更薄的层（络合物）可以对宏观行为产生类似的影响。尽管传统的高分辨率TEM研究没有在完全处理的液相烧结尖晶石中识别出残留的LiF，但是像Li和F这样的轻元素在许多边界络合物的典型量中不能通过这种技术检测到，因此很可能亚纳米层的边界LiF确实是差的边界强度的背后。该计划将在一组高度协调的实验中测试这一命题，这些实验将掺杂晶界的机械性能与其相关的晶界化学和结构相关联。这将通过结合尖端的像差校正扫描透射电子显微镜（ac STEM）和新开发的适用于评估边界局部断裂特性的微尺度断裂测试技术来实现。该计划的结果将为开发用于航天器窗口、传感器圆顶、装甲、护目镜和面罩的透明、耐腐蚀尖晶石材料提供信息。虽然界面肤色的研究还处于早期阶段，但拟议工作的长期影响是通过一个关键因素（边界断裂行为和肤色之间的联系）对记录，理解和利用陶瓷材料中肤色的发展科学框架的贡献。在许多陶瓷（甚至金属）系统中，通过根据复合物框架定制晶界结构和化学，有很大的潜力实现独特的性能组合。可以使用商用仪器进行的微尺度断裂技术的开发将首次为大量人员和行业提供直接参与使用非常小体积的材料进行定量断裂测量的机会。对人类发展的影响将主要通过对参与该项目的研究生和本科生进行教育和培训，他们将获得最新的显微镜和微测试技术。将通过继续参与外展活动对当地社区产生影响，包括？纳米日位于宾夕法尼亚州阿伦敦的达芬奇科学技术发现中心。