Building Ceramic Metamaterials from Nanoparticles: A combined Modelling, Tomography and In-situ Loading Study.

材料表征对于其物理、化学和机械性能的量化和预测至关重要：60多年来，分子模拟为实验提供了独特的见解和预测。然而，新（纳米）材料的合成结构越来越复杂，可能很快就不可能产生足够现实的模型来充分描述它们。分子模拟通过利用系统的对称性和基原子的坐标来产生三维周期性的晶体阵列。在这里，我们开创了一种新的系统方法来规定纳米材料的结构。具体来说，模拟代码将通过利用纳米材料的空间对称性和将纳米粒子而不是原子定位在基位上，从而能够系统地生成纳米结构；分子动力学将用于使纳米构建块形成纳米材料的壁。与此同时，实验（自下而上）将用于合成纳米粒子，包括它们自组装成有序连接和无序连接的超结构。自上而下的制造纳米结构的方法将通过聚焦场发射电子束来实现，这将使纳米结构以低于10nm的分辨率钻成单晶。实验工作的核心将是对建模过程的验证和确认。其中一项关键技术是纳米层析成像，它可以分辨纳米结构深处的区域。在这里，透射电子显微镜（TEM）中的层析技术将用于绘制三维元素分布和三维形态（面形分布），从而可以提取定量参数，包括连通性和表面积。这种三维计量数据将直接与建模预测进行比较。层析成像技术将用于三维表征超材料，不仅将提供对纳米材料内部结构的前所未有的深入了解，而且还将为原子模型提供必要的验证。配备（经过验证的）结构模型，将计算杨氏模量、弹性常数等力学性能，模拟应力-应变曲线以及化学性能，包括表面反应性（催化、传感器）和离子传输（燃料电池、可充电电池）。纳米力学测试：创新的现场纳米尺度机械变形测试，采用谢菲尔德的原位TEM NanoLAB设备进行局部力测定，将用于测量机械性能。这将提供对纳米尺度工程规则的基本见解，并验证力学性能模拟。在TEM的试样室中进行压缩和拉伸测试，我们将提取机械弹性和塑性性能的关键参数，并将其与建模预测进行比较。机械测试为模型提供了严格的测试，因为它们必然会受到所有三个复杂层次结构的影响——多晶结构、微观结构（晶界、位错、点缺陷）和纳米结构。一旦模拟的性质得到验证，它们将被预测性地使用：将构建相关表来探索纳米（结构）如何影响性质。我们提出，完美的性质与全近表面纳米材料的结构协同作用将提供独特的机械和化学性能。对于体模拟，缺陷-如杂质，夹杂物，位错和双边界生成机制提供了断裂和塑性崩溃的载体。相反，没有这种缺陷的微观结构和限制位错力学的纳米材料将承受显著的载荷。

Materials characterization is crucial for the quantification and prediction of their physical, chemical and mechanical properties: Molecular simulation has provided experiment with unique insight and prediction for over 60 years. However, new (nano)materials are being synthesized with ever increasing structural complexity and it may soon prove impossible to generate models that are sufficiently realistic to describe them adequately.Molecular simulations proceed by using the symmetry of the system, together with the coordinates of the basis atoms to generate a crystallographic array, periodic in three dimensions. Here, we pioneer a new systematic approach to prescribe the structure of a nanomaterial. Specifically, a simulation code will enable the systematic generation of a nanostructure by exploiting the space symmetry of the nanomaterial and positioning nanoparticles, rather than atoms, at basis positions; molecular dynamics will be used to enable the nanobuilding blocks to formulate the walls of the nanomaterial. In parallel, experiment (bottom up) will be used to synthesise nanoparticles including their self-assembly into order-connected and disordered-connected superstructures. Top down approaches to fabricate nanoscale architectures will be achieved by focused field-emission electron beams, which will drill nanoarchitectures into single crystals with sub 10nm resolution.Central to the experimental work will be the verification and validation of the modelling process. One key-technology, which can resolve areas deep within the nanostructure, is nanotomography. Here tomographic techniques in the transmission electron microscope (TEM) will be used to map the 3D elemental distribution and 3D morphology (faceting distribution) such that quantitative parameters, including connectivity and surface area can be extracted. This 3D metrology data will be compared directly to the modelling predictions. Tomographic techniques will be used to characterise the metamaterials in three-dimensions and will not only provide unprecedented insight into the structural architectures deep within the nanomaterials, but also provide essential validation for the atomistic models.Equipped with (validated) structural models, mechanical properties, such as Youngs modulus, elastic constants will be calculated and stress-strain curves simulated together with chemical properties, including surface reactivity (catalysis, sensor) and ionic transport (fuel cells, rechargeable batteries). Nanomechanical testing: Innovative in-situ nanoscale mechanical deformation tests with local force determination using Sheffield's In-Situ TEM NanoLAB facility will be used to measure the mechanical properties. This will provide fundamental insight into the engineering rules at the nanoscale and validate the mechanical property simulations.Compression and tensile testing in the specimen chamber of a TEM we will extract key-parameters on mechanical elastic and plastic properties, which will be compared with modelling predictions. Mechanical tests provide a stringent test of the model because they will necessarily be influenced by the structure on all three hierarchical levels of complexity - polymorphic structure, micro-structure (grain-boundaries, dislocations, point defects) and nanostructure.Once the simulated properties have been validated, they will be used predictively: Correlation tables will be constructed to explore how the nano(structure) influences the properties.We propose that the flawless nature in synergy with the architecture of entirely near-surface nanomaterials will proffer unique mechanical and chemical properties. For the bulk analogue, defects - such as impurities, inclusions, dislocations and twin boundary generation mechanisms provide vehicles for fracture and plastic collapse. Conversely, a nanomaterial, with no such defective microstructure and restrictive dislocation mechanics, will sustain remarkable loadings.