2021年3月8日
Researchers from Tokyo Metropolitan University have studied the properties of mixtures of silicone-coated "magic sand", a popular kid's toy, and normal sand. Silicone-coated sand particles were found to interact with each other only, and not with other sand particles.
The team discovered that adding silicone-coated sand beyond a certain threshold leads to an abrupt change in clustering and rigidity, a simple, useful way to potentially tune the flow of granular materials for industry.
沙子是一种引人入胜的材料。它可以像液体一样流动并倒入，但保留了许多固体特性，堵塞管道或形成沙丘。小颗粒（如沙）的集合的行为称为yabo214颗粒物理学，对于处理和运输各种颗粒状材料，例如谷物，大米，粉末以及建筑业中使用的大量沙子，也是一个非常重要的领域。亚博网站下载
该物理分支的关键难题是涉及的纯粹数字。谷物通过简单的牛顿力学相互作用，但是由于如此多的粒子一次相互作用，因此流动行为的出现复杂性尚无法通过简单方程来解释。yabo214因此，科学家不仅在寻找更好的理论模型来解释颗粒状行为，而且还可以在实验室中处理和调整方便的“模型系统”，以洞悉颗粒材料的微观结构如何产生其宏观特性。亚博网站下载
由助理教授玛丽·塔尼（Marie Tani）和东京大都会大学（Tokyo Metropolitan University）的雷伊·库里塔（Rei Kurita）教授领导的团队一直在研究潮湿时沙子会发生什么。众所周知，海滩砂的行为完全不同。干燥时，沙堡的建造将很棘手！这种行为在很大程度上是由于颗粒之间液体的“桥”形成，称为yabo214capillary bridges, strongly tying grains together to form load-bearing structures.
However, homogeneous wet sand is notoriously hard to prepare in the lab; it's hard to mix evenly, and dries very quickly. To overcome this issue, they instead used "magic sand," hydrophobic sand particles coated in silicone oil, commonly available as a kid's toy.
The team found that not only does "magic sand" strongly attract each other via thin strands of oil, but it completely ignores normal sand, simply bumping into it like dry grains. By mixing "magic sand" and normal sand in different ratios, the team could freely study how wet sand behaves down to even the smallest liquid fractions, where only some grains are connected via capillary bridges.
Using three independent methods involving sieving, measuring density and forming stable mounds of sand, they found that the mechanical properties of the mixture changes drastically when the fraction of magic sand to normal sand exceeds 20%.
这与渗滤理论的发现一致，该发现研究了粒子之间的连接如何跨越空间而没有任何破裂，使沙子混合物的行为更加固体状并承担自身的重量。yabo214这种行为以聚合物凝胶而闻名，并有助于统一应用于完全不同材料的理论方法。亚博网站下载
The team's mixtures also provide a convenient material for industry with mechanical properties that can be easily modified. Importantly, the method provides a new, convenient, accurate and informative way to explore granular physics, and may become the new default for scientists in future investigations.
This work was supported by JSPS KAKENHI Grants-in-Aid for Scientific Research (20K14431, 17H02945, and 20H01874).
Source:https://www.tmu.ac.jp/english/index.html