Mechanical behavior of bulk supercrystalline ceramic-organic nanocomposites

块体超晶陶瓷有机纳米复合材料的力学行为

• 批准号: 429317750
• 负责人: Diletta Giuntini, Ph.D.
• 金额: --
• 依托单位: Department of Mechanical Engineering
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2023-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/429317750?language=en
• 关键词: Mechanical; behavior; bulk; supercrystalline; ceramic

The proposed work aims at elucidating the mechanical behavior of bulk supercrystalline ceramic-organic nanocomposites. These are materials that consist of inorganic, usually crystalline, nanoparticles, surface-functionalized with organic ligands, and assembled into periodic structures, analogous to atomic lattices. They represent a rising field of materials science and nanoengineering, which has been finding applications in optoelectronics, plasmonics, magnetic materials, battery electrodes, catalysts and sensors. Their use for structural purposes is however largely unexplored, even if promising mechanical properties have started to emerge in bulk ceramics-based supercrystalline materials.An effective way to enhance their mechanical properties has been found in inducing crosslinking among the organic chains that are anchored to the ceramic nanoparticles’ surfaces. This limits the mobility of the inorganic building blocks with respect to each other, leading not only to high values of strength, hardness and stiffness, but also to significant changes in the materials’ behavior under loading. Preliminary work points towards the concurrent effects of material compaction, plastic-like deformation and extrinsic toughening mechanisms. Defects remindful of the ones typically observed in crystalline materials – such as interstitials, stacking faults, dislocations and shear bands – have also been detected.The interconnections among mechanical behavior and the local nanostructure deformations are yet to be clarified, and this is what the present proposal aims at tackling. For materials with various degrees of crosslinking of the organic ligands, the stress-strain relationships, creep and compressibility behavior are to be derived. In parallel, the defects and deformations induced by both material processing and mechanical loading will be characterized. The methods of choice involve nanoindentation with various tips, for the derivation of the materials’ constitutive response, and atomic force and electron microscopy for the visualization of imperfections, from point-defects to dislocations and inter-supercrystalline boundaries. Together with their empirical evaluation, the connections between supercrystalline deformations and overall mechanical behavior will be modeled by applying and adapting the classic theories from the literature on slip systems activation, strain and stress fields around line defects, and dislocation glide. The correlations between material processing, supercrystalline structure and mechanical properties will then be inferred.

提出的工作旨在阐明块体超晶陶瓷-有机纳米复合材料的力学行为。这些材料由无机的，通常是晶体的纳米颗粒组成，表面被有机配体功能化，并组装成类似原子晶格的周期性结构。它们代表了材料科学和纳米工程的一个新兴领域，已经在光电子学、等离子体学、磁性材料、电池电极、催化剂和传感器中得到了应用。然而，它们在结构用途上的应用在很大程度上尚未被探索，即使在大块陶瓷基超晶材料中已经开始出现有希望的机械性能。提高陶瓷纳米颗粒机械性能的有效方法是诱导固定在陶瓷纳米颗粒表面的有机链之间的交联。这限制了无机建筑块之间的流动性，不仅导致高强度、硬度和刚度，而且还导致材料在载荷下的行为发生重大变化。初步的工作指向材料压实、类塑性变形和外在增韧机制的共同作用。还发现了晶体材料中常见的缺陷，如间隙、层错、位错和剪切带。机械行为和局部纳米结构变形之间的相互关系尚未得到澄清，这正是本提案旨在解决的问题。对于具有不同程度有机配体交联的材料，导出了应力-应变关系、蠕变和压缩行为。同时，材料加工和机械载荷引起的缺陷和变形将被表征。选择的方法包括各种尖端的纳米压痕，用于推导材料的本构响应，原子力和电子显微镜用于观察缺陷，从点缺陷到位错和超晶间边界。结合他们的经验评估，超晶变形和整体力学行为之间的联系将通过应用和改编关于滑移系统激活、线缺陷周围的应变和应力场以及位错滑动的经典理论来建模。然后推断出材料加工、超晶结构和机械性能之间的相关性。