CAREER: Consecutive Assembly-and-Mineralization Processed Calcium-Silicate-Hydrate Nacre with High Specific Flexural Strength and Fracture Toughness

这一学院早期职业发展(CALEAR)计划将应对转变硅酸钙(CSH)-水泥的主要成分，并获得前所未有的机械性能-的挑战。CSH在压缩下具有较高的强度，但在弯曲下强度明显较弱，断裂韧性较低。CSH纳米结构的不规则性和无序性是其脆性的原因。这项研究将创新新的CSH纳米结构，灵感来自珍珠层的独特结构，它是超轻的，被公认为最强大的生物材料之一。模拟天然珍珠层的生长，用聚合物和有机物合成CSH，形成高度有序的珍珠层状结构。这项研究将创造出与天然珍珠层一样抗裂的新型水泥基材料，这将极大地提高土木工程结构(如预制墙和建筑物面板、隧道或管道衬砌和桥梁永久模板)、能源基础设施(如太阳能电池板、海上风电场)、航空航天结构和其他结构的弹性、可持续性和耐久性。该项目的教育和推广活动将使K-12学生和STEM学科中代表性不足的少数群体有机会了解工程学中的仿生材料和结构。这项研究的目的是证明这样一个假设，即CSH珍珠岩结构可以通过模拟天然珍珠岩生长的连续组装和矿化过程来获得高比抗折强度和断裂韧性。这项研究的主要目标是：(I)开发合成和控制CSH介晶生长的方法；(Ii)开发连续的组装-矿化工艺以实现CSH珍珠层的可伸缩制造；(Iii)表征合成CSH珍珠层的力学性能；以及(Iv)建立制造工艺、微结构和力学性能之间的联系，以优化CSH珍珠层。为此，首先通过冷冻浇注制备支架，然后通过控制矿化在支架上成核和生长CSH介晶；然后通过有机相渗透和热压合成层状CSH珍珠层。CSH珍珠层将通过实验、建模和机器学习进行测试和优化。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This Faculty Early Career Development (CAREER) program will address the challenge to transform calcium-silicate-hydrate (CSH) - the ingredient of cement that is primarily responsible for its strength - and achieve unprecedented mechanical properties. CSH has high strength under compression, but is significantly weaker under bending and has low fracture toughness. The irregular and random nature of the nanostructure of CSH is responsible for its brittle nature. This research will innovate new CSH nanostructures that are inspired by the unique architecture of nacre, which is ultra-lightweight and recognized as one of the strongest biomaterials. The growth of natural nacre will be mimicked to synthesize CSH with polymers and organics to form highly ordered nacre-like architectures. This research will create novel cement-based materials with crack resistance as high as that of natural nacre, which will tremendously enhance the resilience, sustainability, and durability of civil engineering structures (such as prefabricated walls and panels of buildings, linings of tunnels or pipelines, and permanent formwork of bridges), energy infrastructure (such as solar panels, offshore wind farms), aerospace structures and others. The education and outreach activities of this project will engage and create opportunities for K-12 students and underrepresented minorities in STEM disciplines to learn about biomimetic materials and structures in engineering. The goal of this research is to demonstrate the hypothesis that CSH nacre architecture can be synthesized to achieve high specific flexural strength and fracture toughness through a consecutive assembly-and-mineralization process mimicking the growth of natural nacre. The main objectives of this research are to: (i) develop methods to synthesize and control growth of CSH mesocrystals; (ii) develop a consecutive assembly-mineralization process for scalable fabrication of CSH nacre; (iii) characterize mechanical properties of the synthetic CSH nacre; and (iv) establish links for the fabrication process, microstructure, and mechanical properties to optimize the CSH nacre. To this end, a scaffold will first be fabricated by freeze casting and followed by nucleation and growth of CSH mesocrystals on the scaffold through controlled mineralization; then, laminated CSH nacre will be synthesized through organic phase infiltration and hot-pressing. The CSH nacre will be tested and optimized by experiments, modeling, and machine learning.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.