Characterizing the spatiotemporal evolution of paramagnetic colloids in time-varying magnetic fields with Minkowski functionals
Characterizing the spatiotemporal evolution of paramagnetic colloids in time-varying magnetic fields with Minkowski functionals
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DOI：
10.1039/d0sm01100b
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发表时间：
2020-10-14
期刊：
影响因子：
3.4
通讯作者：
Biswal, Sibani Lisa
中科院分区：
文献类型：
--
作者：
Hilou, Elaa;Joshi, Kedar;Biswal, Sibani Lisa
相分离技术被广泛应用于将复杂的流体组装成新材料。由于浓度、压力或温度的变化，这些分离过程可以由热力学驱动。相分离也可以被外部刺激，如磁场诱导，导致新的非平衡系统。然而，外界刺激如何影响时相之间的转换路径还没有详细的探讨。在这里，我们描述了超顺磁性胶体在时变磁场中的相分离动力学。最初均一的胶体悬浮液可以通过调幅节点分解形成的双连续相，从带有空洞的连续胶体相转变为离散的胶体团簇。转变的类型取决于粒子的浓度和外加磁场的大小。通过Minkowski泛函对微观组织的分析，量化了形核和生长过程中微观组织的时空演化。胶体体系的特征长度被确定为与系统变量如磁场强度、颗粒浓度和时间呈幂函数关系。了解颗粒浓度和外加磁场之间的相互作用有助于更好地控制在这些磁性可调胶体系统中观察到的相。
Phase separation processes are widely utilized to assemble complex fluids into novel materials. These separation processes can be thermodynamically driven due to changes in concentration, pressure, or temperature. Phase separation can also be induced with external stimuli, such as magnetic fields, resulting in novel nonequilibrium systems. However, how external stimuli influence the transition pathways between phases has not been explored in detail. Here, we describe the phase separation dynamics of superparamagnetic colloids in time-varying magnetic fields. An initially homogeneous colloidal suspension can transition from a continuous colloidal phase with voids to discrete colloidal clusters, through a bicontinuous phase formed via spinodal decomposition. The type of transition depends on the particle concentration and magnitude of the applied magnetic field. The spatiotemporal evolution of the microstructure during the nucleation and growth period is quantified by analyzing the morphology using Minkowski functionals. The characteristic length of the colloidal systems was determined to correlate with system variables such as magnetic field strength, particle concentration, and time in a power-law scaling relationship. Understanding the interplay between particle concentration and applied magnetic field allows for better control of the phases observed in these magnetically tunable colloidal systems.