材料的强度和韧性是衡量其力学性能的两个重要指标，足够的强度和韧性是材料在实际工程应用中可靠性和安全性的基本保障。石墨烯等二维材料因其优异的面内性能而有着非常广泛的应用。但如何提升其强度和韧性，以及基于二维材料构筑具有高强度和高韧性的三维结构都面临巨大挑战，这些挑战极大地限制了二维材料的应用。本文基于单原子层非晶碳材料（monolayer amorphous carbon, MAC）的强韧机理及三维构筑开展研究，取得的主要创新性成果如下：

（1）揭示了由缺陷诱导的表面粗糙度和单原子层固有的柔性带来高强度和类塑性大变形的新机制，设计了两种同时实现高强度和高韧性的三维结构，为提高范德华异质结构的韧性，有效避免灾难性失效提供了新的策略。

（2）通过验证两种原子尺度离散系统J积分的计算方法，发现了域J积分法在原子尺度断裂性能计算上的有效性。

（3）揭示了晶格无序引起的纳米尺度褶皱是二维材料增韧的核心要素这一新机理，并通过在石墨烯中构造纳米尺度褶皱验证了其普适性。此外，石墨烯的缺陷工程增韧需要在原子级精度上进行结构调控，目前的技术水平难以达到。故本文提出的纳米级褶皱增韧方法由于MAC具有良好可控性和重复性的制备工艺，在增韧其他二维材料的工程实践中更具可行性。

类似于微观系统中原子的晶格无序排布会带来新现象，在宏观多相掺杂系统中，掺杂相无序地分布在基体中也会极大地改变基体的性质。本文以聚合物中无序掺杂玻璃微球组成的超材料为研究对象，发现极少量无序分布的微球将使材料表现出独特的光谱选择吸收性，并深入研究了微球的半径、体积分数和材料厚度对其辐射冷却效率的影响。

Strength and toughness are two critical mechanical properties of a material, which are required to be high enough to ensure the reliability and safety of the material in practical engineering applications. Two-dimensional(2D) materials, such as graphene, are promising candidates for various applications owing to their excellent in-plane properties. However, improving their strength and toughness and the scale-up of 2D sheets as building blocks for three-dimensional(3D) materials with high strength and toughness are facing significant challenges. Based on monolayer amorphous carbon (MAC), the mechanism of strengthening and toughening and 3D scale-up are studied here and following innovative results are obtained:

1. A counter intuitive mechanism that surface roughening due to initial defects and low rigidity may help to realize superb mechanical properties in 3D aggregation of monolayer carbon is demonstrated. Two 3D structures with high strength and toughness are designed. Our results pave a new strategy in enhancing toughness in van der Waals heterostructures to effectively avoid catastrophic failure.
2. The domain J-integral method is proved to be effective and reliable in analyzing the fracture properties of atomic scale discrete systems by verifying the contour and domain J-integral methods.
3. It is shown that lattice disorder results in nanoscale ripples which can alleviate stress concentration in the vicinity of crack-tips and render MAC flaw tolerant. This nnvel mechanism is proved to be general by introducing nanoscale ripples into graphene sheets. In engineering practice, the routine to make MAC can be well-controlled and is repeatable, and is of particular interest from the manufacture aspect, in contrast to precise defect engineering in graphene. Therefore, our findings should be generally applicable to toughening of many different classes of 2D materials via a practically achievable experimental route.

Similar to the lattice disorder bringing in new phenomena, randomly distributed particles in composites also make great contributions in alter the properyies of the material. It is found that the polymer matrix shows spectral selective absorbency by adding low concentration of microspheres with randomly diatribution. And the effects of microsphere radius, volume fraction and film thickness on radiative cooling efficiency were investigated.