Shear bands and the evolving microstructure in a drying colloidal film studied with scanning µ-SAXS.
Shear bands and the evolving microstructure in a drying colloidal film studied with scanning µ-SAXS.
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DOI：
10.1038/s41598-018-31405-6
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发表时间：
2018-08-28
影响因子：
4.6
通讯作者：
Smith MI
中科院分区：
文献类型：
--
作者：
Yang B;Smith ND;Johannes A;Burghammer M;Smith MI
薄带中的剪切局部化是应力作用下材料塑性变形的一个重要过程。该过程通常对样品的微观结构（非晶/结晶）敏感。在这里，我们使用扫描µ-SAXS技术，这些不同的微观结构如何影响干燥胶体膜中的塑性变形。在结晶样品中，通过在20重量%样品中的散射图案中的六重对称性的发展，直接确定在压实前的有序过渡的存在。它示出了在压实过程中的颗粒的各个群体的塑性变形可以跟踪和测量在真实的时间。发现更高浓度的悬浮液导致无定形结构。晶体和非晶微观结构与初始颗粒浓度之间的过渡也被发现与剪切带的外观。通过二维空间映射的局部薄膜结构，剪切带在薄膜中的存在是直接相关的应变大小和压缩方向的微尺度空间变化。我们的测量还表明，剪切带导致局部颗粒体积分数减少约1- 2%，表明显着的疏水性。
Shear localisation in thin bands is an important process involved in the plastic deformation of materials subject to stress. This process is often sensitive to the sample microstructure (amorphous/crystalline). Here we show using the scanning µ-SAXS technique, how these different microstructures influence the plastic deformations in a drying colloidal film. In crystalline samples, the presence of an ordering transition at the compaction front was directly identified through the development of a six-fold symmetry in the scattering pattern in 20 wt% samples. It is shown that plastic deformations in individual groups of particles during the compaction process can be tracked and measured in real time. Higher concentration suspensions were found to result in amorphous structures. The transition between crystalline and amorphous microstructures with initial particle concentration was also found to correlate with the appearance of shear bands. Through 2D spatial mapping of the local film structure, the presence of shear bands in the films was directly related to the microscale spatial variations in strain magnitude and compression direction. Our measurements also showed that shear bands lead to a reduction in the local particle volume fraction ~1–2%, indicating significant dilatancy.