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

对控制沉降法制备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尺寸分布的功能梯度材料，样品能够保持在通过烧结。这一实验结果也反映在考虑粒度分布效应的模拟结果中。一般来说，烧结功能梯度陶瓷往往会引入缺陷。尽管存在这些常见问题，但本研究中考虑的不对称结构具有垂直功能，即结构中连续重叠的广泛粉末尺寸分布。这种排列有助于均匀化烧结速率。与此相关的模型表明，这种结构可以很容易地烧结而不会翘曲或开裂。为了证明这些影响，采用有限元法数值模拟多孔非对称陶瓷结构的烧结特性，将粉末粒度分布作为场变量纳入模型中。能够预测非翘曲结构的关键是将粉末粒度分布纳入模型。在整个结构的垂直截面上，分布广泛且重叠，都有一个明显的细尾。这些特性加速并均匀了局部烧结速率，因此最终的结果是无翘曲的熔融结构。这项工作提出了烧结模型的新进展，从而可以证明粒径分布效应对所需产品性能的贡献。这些对模型的补充产生的数值结果与观察到的物理样品的结构剖面相匹配。样品的几何形状、孔隙度和粒度分布演变与物理样品的测量一起被追踪。总的来说，该模型与实验观测吻合得很好。对观察到的趋势的正确计算为模型中包含的潜在烧结机制提供了信心。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