Theoretical and experimental study of optimal sintering condition for flat ceramic substrates with graded porous structure

对用可控沉积技术制备的多孔氧化铝结构的烧结过程进行了数值模拟。通过形成这种具有非常宽的粉末粒度分布的功能梯度材料，样品能够在烧结过程中保持不变。这一实验结果反映在目前的模拟结果中，该模拟结果考虑了颗粒分布的影响。一般来说，烧结功能梯度陶瓷经常会引入缺陷。尽管存在这些常见的问题，但本工作中考虑的不对称结构具有垂直功能，即在结构中连续重叠广泛的粉末粒度分布。这种安排起到了使烧结率均匀的作用。与此相关的建模表明，这种结构可以很容易地烧结，而不会翘曲或开裂。为了验证这些影响，开发了一种有限元数值模拟方法来模拟多孔非均匀…的烧结特性。通过将粉末粒度分布作为场变量加入到模型中，能够预测非翘曲结构的关键是将粉末粒度分布引入到模型中。在结构的垂直截面上，分布广泛且重叠，均有明显的细小尾巴。这些特性加速和均化了局部烧结速度，最终结果是无翘曲的熔融结构。这项工作在烧结模型方面取得了新的进展，从而可以证明粒度分布效应对所需产品性能的贡献。这些对模型的补充产生了与观测到的物理样品的结构轮廓相匹配的数值结果。在对物理样品进行测量的同时，跟踪了样品的几何形状、孔隙率和颗粒尺寸分布的演变。总体而言，该模型与实验观测结果吻合较好。对观察到的趋势的正确核算为模型中包含的潜在烧结机制提供了信心。较少

A numerical simulation is presented on the sintering of porous alumina structures prepared by a controlled sedimentation technique. By forming this functionally gradient material with a very broad powder size distribution, the samples were able to remain at through sintering. This experimental result is reflected in the present simulation results which incorporated particle size distribution effects.In general, sintering functionally gradient ceramics can often introduce defects. Despite these common problems, the asymmetric structures considered in this work featured a vertical functionality of continuously overlapping broad powder size distributions in the structure. This arrangement served to homogenize sintering rates. Modelling presented in connection with this shows that such structures can be readily sintered without warpage or cracking. To demonstrate these effects, a finite element method numerical simulation was developed to model the sintering characteristics of porous asymm … More etric ceramic structures by incorporating the powder particle size distribution into the model as a field variable.The key for being able to predict a non-warped structure was the incorporation into the model of the powder particle size distribution. Across the vertical section of the structure, the distributions were broad and overlapping, all with a significant fines tail. These characteristics accelerate and homogenize local sintering rates, such that the net result is a non-warped fused structure.This work presented novel advances in the sintering model such that the contributions to the desired product properties attributable to particle size distribution effects can be demonstrated. These additions to the model produced numerical results which properly match observed structural profiles of physical samples. Sample geometry, porosity and particle size distribution evolutions were traced alongside measurements made on physical specimens. In general the model corresponded well with the experimental observations. The correct accounting of observed trends lends confidence to the underlying sintering mechanisms incorporated into the model. Less