Interactions between Nanoparticles and Polymers in the Diffusion Boundary Layer during Freezing Colloidal Suspensions
Interactions between Nanoparticles and Polymers in the Diffusion Boundary Layer during Freezing Colloidal Suspensions
复制标题
冷冻胶体悬浮液期间扩散边界层中纳米颗粒和聚合物之间的相互作用
DOI：
10.1021/acs.langmuir.9b00806
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发表时间：
2019
期刊：
影响因子：
3.9
通讯作者：
Zhu Yaochan
中科院分区：
文献类型：
--
作者：
You Jiaxue;Wang Jincheng;Wang Lilin;Wang Zhijun;Li Junjie;Lin Xin;Zhu Yaochan
本文研究了胶体悬浮液冷冻过程中纳米颗粒与聚合物之间的扩散相互作用。探讨了纳米颗粒堆积形成的纳米多孔介质对聚合物溶液扩散不稳定性的尺寸效应。结果表明，在较低的拉伸速度下，小颗粒会阻碍聚合物的扩散，相应的形貌为带状结构。其内在原因是纳米多孔颗粒层中聚合物链的管状运动受到抑制。增大颗粒尺寸或减小溶质尺寸将解决扩散问题。另一方面，较小的牵引速度在凝固界面前构造了增加的颗粒层长度，这呈现出较长的扩散路径以阻碍聚合物扩散。相反，增加的牵引速度缩短了颗粒层的长度，使得聚合物容易通过短的多孔介质。因此，聚合物的扩散将控制悬浮液的冷冻形态并产生枝晶。这些结果表明，相对较大的颗粒尺寸和适度较高的拉速有利于良好的显微结构，在多孔陶瓷的生产与冷冻铸造法。
The present work investigated diffusion interactions between nanoparticles and polymers during freezing colloidal suspensions. The size effects of nanoporous media formed by packed nanoparticles on the diffusion instability of the polymer solution were explored. It is found that small particles under low pulling speeds will obstruct the diffusion of polymers and the corresponding morphology will be banded structures. The intrinsic reason is the inhibited tube-like motion of polymer chains in the nanoporous particle layer. The increased particle size or the decreased solute size will solve the diffusion problem. On the other hand, the small pulling speed constructs an increased length of the particle layer in front of the freezing interface, which presents a longer diffusion path to impede the polymer diffusion. Instead, an increased pulling speed shortens the length of the particle layer so that it is easy for polymers to go through a short porous media. Hence, the diffusion of polymers will control the freezing morphology of the suspension and create dendrites. These results imply that a relatively larger particle size and a moderately higher pulling speed are beneficial for well-developed microstructures in the production of porous ceramics with the freeze-casting method.