基于分形理论的电磁功能化结构陶瓷的微观形貌调控逾渗效应研究

With the rapid development of information technology, there is a growing demand for the electromagnetic compatibility (EMC) of electronic devices to suppress the increasing electromagnetic interference, whereas various conventional accessional electromagnetic shielding and filtering materials can not meet the further requirement of miniaturization, integration and multi-functionalization. To solve this problem, this project proposes a novel EMC solution to functionalize the inner structural components of alumina ceramics in the electronic devices with magnetic particles. Considering two nonlinear effects of the mechanical and electromagnetic properties of materials and the recent research progress, a key scientific issue that the magnetic percolation of the composites can be modulated by the variation of the microstructure has been proposed. In this project, we attempt to control the microstructure and morphology of the alumina / ferrite composites through three different preparation methods. The fractal dimensions of the morphology will be then determined in terms of the fractal theory. The relationship between the fractal dimension and the percolation threshold as well as the performance variation of electromagnetic properties will be quantitatively analyzed and modeled. The ultimate aim of this project is to tailor the electromagnetic properties of the composites through morphology control, which is crucial to the potential applications of structural ceramics in the EMC and other multifunctional fields.

随着电子信息技术的发展，电磁干扰的危害日益凸显，人们对电子设备电磁兼容性的要求越来越高，而各类外加或内置的电磁屏蔽及滤波材料不能满足电子器件小型化、集成化、多功能化的发展需求。针对这一问题，本项目提出了电子设备自身的氧化铝结构部件电磁功能化的电磁兼容解决方案，结合材料力学性能及电磁性能的两种非线性效应以及目前研究现状，总结出微观相貌调控电磁逾渗效应的关键科学问题；本项目拟利用粒径调整法、坯体浸渗法以及固溶体析出法等方法实现氧化铝/铁氧体复合材料的不同微观形貌与磁性相分布的可控化制备，采用分形理论确定不同微观形貌的分维值，建立分维值与电磁逾渗阈值及性能变化规律的定量关系模型，最终实现通过微观形貌调控复合材料电磁性能的目的。这一项目的研究将为结构陶瓷材料在电磁兼容等领域的结构功能一体化应用提供科学依据。

本项目基于结构陶瓷复合材料的颗粒弥散强化和电磁逾渗效应这两种非线性效应，通过在结构陶瓷基体中添加磁性颗粒复合相，实现了结构陶瓷材料的电磁功能化。项目系统制备和研究了多种结构陶瓷/磁性颗粒复合材料体系，通过调控复合材料的组成以及微观形貌，揭示了复合材料力学性能和电磁性能的协同变化规律，获得了与预期一致的非线性协同变化效应；重点研究了不同复合材料体系的电磁逾渗效应，确定了几种材料体系的逾渗阈值及其在阈值附近的性能变化规律，获得了复合材料介电常数逾渗阈值调控的主要影响因素及调控工艺条件；总结了磁性材料微观形貌与电磁性能的变化规律，研究了复合材料中磁性相分布对电磁性能的影响规律，发明了一种磁性颗粒扁平化制备方法，提出了微观形貌调控电磁性能的方案；通过分析复合材料力学与电磁性能的协同变化行为，评估了复合材料作为电磁功能化结构材料的最优性能，确定了相应的性能平衡点及最佳组分。本项目的研究将促进结构陶瓷材料在电磁兼容等领域的结构功能一体化应用。