Micro Structural Investigations and Mechanical Properties of Macro Porous Ceramic Materials from Capillary Suspensions
Micro Structural Investigations and Mechanical Properties of Macro Porous Ceramic Materials from Capillary Suspensions
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DOI：
10.1111/jace.13184
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发表时间：
2014-12-01
影响因子：
3.9
通讯作者：
Willenbacher, Norbert
中科院分区：
文献类型：
--
作者：
Dittmann, Jens;Willenbacher, Norbert
最近，我们介绍了一种新的、材料无关的加工方法，用于生产以毛细悬浮液为稳定前驱体的宏观多孔陶瓷。毛细管悬浮液是一种三相系统，其中向悬浮液中加入少量不混溶的二次液体，从而形成样品跨越粒子网络。该技术可提供50%以上的孔隙度，孔径范围为0.5-100m。本文重点研究了毛细管悬浮液中微观结构的形成及其对烧结件机械强度的影响。根据流变学数据和扫描电镜图像，确定了三种状态（I、II、III），随着二次液相添加量的不同，湿悬浮液的流动特性和烧结陶瓷部件的特征结构也有明显的不同。随着二次液相量的增加，平均孔径增大，孔径分布由单峰型(I)变为双峰型（II）和宽多峰型（III）。在(I)和（II）中观察到湿悬浮液的屈服应力与孔隙率和孔径之间存在明显的相关性。抗压强度和抗弯强度以及杨氏模量随二次液相量的增加而单调降低。绝对值主要由孔隙度决定，对于对应于(I)和（II）的样品，可以用Gibson & Ashby模型很好地预测。（III）状态下的宽孔径分布导致机械强度显著降低。
Recently, we have introduced a novel, material-independent processing method for producing macro porous ceramics with capillary suspensions as a stable precursor. A capillary suspension is a three-phase system where a small amount of an immiscible secondary liquid is added to a suspension resulting in the formation of a sample spanning particle network. This technology provides open porosities well above 50% and pore sizes ranging from 0.5-100m. Here we focus on microstructure formation in the capillary suspensions and its impact on mechanical strength of the corresponding sintered parts. Based on the rheological data and SEM-images, three regimes (I, II, III) are identified with distinctly different flow properties of the wet suspension and characteristic structural features of the sintered ceramic parts depending on the amount of added secondary liquid phase. The average pore size increases and the pore size distribution changes from monomodal (I) to bimodal (II) and broad multimodal (III) with increasing amount of secondary liquid phase. A clear correlation between the yield stress of the wet suspension and the porosity and pore size is observed for regime (I) and (II). Compressive and flexural strength as well as the Young's modulus monotonically decrease with increasing amount of the secondary liquid phase. Absolute values are mainly determined by the porosity and are well predicted by the Gibson & Ashby model for samples corresponding to regime (I) and (II). The broad pore size distribution in regime (III) results in a significantly lower mechanical strength.