受约束薄膜各向异性烧结致密化及其连续介质力学模拟

Constrained sintering problems belong to a fundamental science in material science and engineering, characteristic of the universality and practicability. Using the optimization of the prediction and modeling of contrained film sintering as an idea, and taking the modification of contiuum mechanics of sintering and the realization of zero-shrinkage sintering as a research goal, we take a LTCC ceramic, which is a typical material in the field of ceramic packaging, as a typical candidate in this project in order to comparatively investigate macro sintering behavior of cylindrial samples and particulate films on a stiff substrate. The relationship between the substrate constraint, thin film densification, microstructure and film materials was explored. The response of sintering strains to the uniaxial load and the microstructural feature were studied in order to obtain a technique for zero-shrinkage sintering. Based on classic sintering theories (discrete and continuum models), using micro-scale parameters of sintering bodies, we attempt to build constitutive equations for constrained sintering problems. By experimentally determining the densification data of zero-shrinkage sintering of cylindrical samples and thin film sintering, we aim to achieve various tensors of constitutive parameters. At the same time, these parameters as achieved would be used to model the densification behavior of constrained thin films. The research outcomes would be expected to set up experimental and theortical bases for one-category constrained sintering problems such as thin film on a stiff substrate.

针对受约束烧结问题的普遍性、实用性和基础科学性，以优化受约束薄膜烧结行为的预测和模拟为研究思路，完善烧结的连续介质力学理论和实现零径向收缩烧结为研究目的，本项目以低温共烧陶瓷（LTCC）这一在陶瓷封装领域有广泛应用背景的材料为典型代表，类比研究圆柱型块状样品和硬质基板（高纯高密度氧化铝陶瓷）上颗粒薄膜的宏观烧结形变行为，探索基板约束和薄膜的烧结致密化、微结构特征以及薄膜材料自身特征的相关性；研究陶瓷样品烧结形变对单轴载荷的响应及其微结构特征，实现零径向收缩烧结的技术途径；在经典烧结理论（离散模型和连续模型）的基础上，结合烧结体的微观尺度参数，建立适用于受约束烧结问题的连续介质力学本征方程，结合圆柱样品零收缩烧结和薄膜受约束烧结致密化的实验测定，分析计算方程中的本征参数（粘度和泊松系数）张量，并用以模拟受约束薄膜的烧结致密化行为，为深化薄膜烧结等一类受约束烧结问题的研究奠定实验和理论基础。

本基金项目以Dupont 951、Ferro A6M薄膜和银峰LTCC薄厚薄材料为研究对象，借助实验室自行研发的非接触光学膨胀仪和垂直悬挂薄膜烧结方法，实现了对薄膜烧结过程中形变原位观测和数据采集，从而研究了它们在无约束各向同性和受约束各向异性条件下的烧结致密化行为和烧结动力学，实验测定了烧结薄厚膜各向同性和各向异性的粘弹介质力学本征烧结参数，结合对烧结薄膜显微结构的定量分析，实现了对硬质基板、柔性基板以及多层厚膜共烧致密化行为的连续介质力学模拟，丰富了连续介质力学在烧结领域中的应用，深化了一系列受约束薄膜烧结问题的理论认识，为制备复杂的基于LTCC薄膜材料的无源器件奠定了很好的实验和理论基础。