Biomimetic Composites With Amorphous Calcium Carbonate: Linking Microstructure to Mechanical Response

最近的发现表明，许多生物产生无定形碳酸钙不是作为更稳定的方解石的前体，而是作为一种矿物的选择。因此，无定形碳酸钙在生物矿物的形态和结构控制中的关键作用已被认识到。然而，非晶相的形成、稳定和转变的决定因素仍然存在争议，所得到的复合材料的力学响应还没有得到研究。该奖项支持基础研究，通过实验和建模相结合的方法，研究非晶态有机碳酸钙复合材料的机械响应随微结构的变化。调整和优化这种材料的机械性能为开发具有优异性能的仿生材料打开了新的机遇。同时，这项研究解决了有关生物矿化的主要问题，这是一个具有主要生物地球化学、环境和经济意义的主题。这项研究涉及多个学科，包括力学、工程学、材料科学、胶体科学和化学。这种多学科的方法提供了广泛的研究机会。它将通过几个本科生参加相关的研究小组和一个提供入门讲座、实地考察和动手研究的K-12外联计划，帮助扩大代表不足群体的参与。在这个项目中所学到的知识将被整合到各种讲座中，因此它将对工程教育产生积极的影响。在实验室合成了无定形碳酸钙仿生复合材料。本研究旨在建立调整其微观结构的设计参数，考察其微观结构-力学响应关系，并研究其失效机理。实验工作包括吸附和力测量来研究矿物的形成，纳米压痕来研究微结构-机械响应关系，原子力显微镜来研究界面性质和非晶到晶体的转变。建模工作基于剪切变换区理论，这是一个用于模拟非晶态材料破坏变形的统计热力学框架，以及内聚有限元模拟。实验和模型之间的关联将能够揭示新型混杂复合材料力学响应的基本现象，包括(I)通过分级几何和微观结构设计相结合的多尺度韧性机制，(Ii)从分布变形的延性行为到脆性响应和应变局部化的转变，(Iii)玻璃化转变，以及(Iv)界面分离和愈合。

Recent discoveries have revealed that many organisms produce amorphous calcium carbonate not as a precursor for more stable calcite but as a mineral of choice. The crucial role of amorphous calcium carbonate in morphological and structural control of biominerals has thus been recognized. However, the determining factors for the formation, stabilization and transformation of the amorphous phase are still in debate and the mechanical response of the resulting composite has not been investigated yet. This award supports fundamental research to investigate the mechanical response of amorphous-crystalline organic calcium carbonate composites as a function of the microstructure using a combination of experimental and modeling work. Tuning and optimizing the mechanical properties of this material opens new opportunities for the development of biomimetic materials with superior properties. In parallel, this research addresses major questions regarding biomineralization, a topic of primary biogeochemical, environmental, and economic significance. This research involves several disciplines including mechanics, engineering, materials science, colloidal science, and chemistry. This multi-disciplinary approach provides a wide range of research opportunities. It will help broaden participation of underrepresented groups through several undergraduate students in the involved research groups and a K-12 Outreach program offering introductory lectures, field trips, and hands on research. The knowledge gained in this project will be integrated in various lectures and therefore it will positively impact engineering education. The biomimetic composites with amorphous calcium carbonate are synthesized in the laboratory. This research aims at establishing design parameters to tune their microstructure, to scrutinize their microstructure-mechanical response relationship, and to study their failure mechanisms. The experimental work involves adsorption and force measurements to study mineral formation, nanoindentation to study microstructure-mechanical response relationship and atomic force microscopy to investigate interfacial properties and amorphous-to-crystalline transformation. The modeling work is based on the Shear Transformation Zone Theory, a statistical thermodynamic framework for modeling failure deformation in amorphous materials, and cohesive finite element simulations. Correlation between experiments and modeling will enable to uncover fundamental phenomena underlying the mechanical response of the novel hybrid composites including (i) multiscale toughness mechanisms through a combination of hierarchical geometry and microstructure design, (ii) transition from ductile behavior with distributed deformation to brittle response and strain localization, (iii) glass transition, and (iv) interfacial separation and healing.