微尺度液滴可控聚并强化无机纳米颗粒原位分散过程的研究

In-situ dispersion of inorganic nanoparticles into organic systems is of great significance for practical applications of particle materials. The surface modification and dispersion processes are generally performed in water-in-oil (W/O) (micro)emulsion systems, where the coalescence of the dispersed-phase microdroplets as well as the mixing and mass transfer plays an important role. In this project, we propose to develop a novel intensification method for in-situ dispersion of inorganic nanoparticles by controlling the microdroplet coalescence and preparation of dispersions with relatively high content of nanoparticles. The position and opportunity of the droplet collisions are adjusted with the microfluidic devices. Combing with the surface forces, viscous force and inertial force within the confined space, desirable coalescence is accomplished. The fundamentals of the mixing and mass transfer as well as the coalescence could be studied. Research is also conducted to the relationship between surfactant adsorption dynamics and particle nucleation−growth dynamics within the coalescence. The adsorption could be adjusted for the matching of the two processes. The spatial distribution and dispersion of the nanoparticles are investigated in the process of droplet coalescence and consequent flow behavior. On the basis of the characteristic parameters of the microscale system correlated with the coalescence, surfactant adsorption, and particle dispersion, a theoretical model could be developed to predict the coalescence of microdroplets and the in-situ dispersion of inorganic nanoparticles.

无机纳米颗粒在有机体系中的原位分散对于颗粒材料的实际应用具有重要意义，该过程通常基于油包水（W/O）型（微）乳液体系进行颗粒的表面改性与分散，其核心问题在于分散相微尺度液滴聚并及其混合、传质过程可控性的提高。本项目针对这一核心问题，提出发展一种利用微尺度液滴可控聚并强化纳米颗粒原位分散过程的方法，制备颗粒含量较高的分散体产品。通过设计新型微流控设备，调控液滴碰撞方式与时机，结合受限空间内界表面力、粘性力、惯性力等微尺度作用力的调节，提高微尺度液滴聚并的可控性，并考察液滴内混合、传质规律与聚并过程的关系；研究微尺度液滴聚并过程中颗粒成核生长动力学与改性剂吸附动力学的关系与调控方式，实现两种动力学的匹配；考察液滴聚并及流动过程中颗粒空间分布与分散行为的演变规律，总结微尺度特征参数与微尺度液滴聚并、改性剂吸附、颗粒分散行为的关系，建立预测微尺度液滴聚并与颗粒原位分散过程的理论模型。

无机纳米颗粒在有机体系中的原位分散对于颗粒材料的实际应用具有重要意义，原位分散过程通常基于油包水（W/O）型（微）乳液体系进行，其核心问题在于分散相反应物微尺度液滴聚并及其混合、传质过程可控性的提高。本项目针对这一核心问题，发展了一种利用微尺度液滴可控聚并强化纳米颗粒原位分散过程的方法。利用平板型、文丘里结构微通道成功地实现了液滴聚并和改性颗粒的高效分散，改性颗粒的迁移率达到98~99%，分散体中颗粒浓度达到1~6wt%、颗粒平均粒度约为10~30 nm，并体现出较低的黏度和优良的稳定性。量化了表面活性剂吸附动力学与其在颗粒表面吸附行为的关系，确定了在表面活性剂临界胶束浓度之上、之下条件下的吸附时间，并与颗粒成核、生长速率相匹配，提高表面活性剂利用率，抑制颗粒团聚。另一方面，实验研究了液滴聚并及流动过程中颗粒动态分布与相间迁移行为的演变规律，通过分散体中颗粒间作用力的分析，量化了颗粒间距离的动态变化，并在此基础上实现了Ag、Au型等具有表面增强拉曼特性的复合薄膜的可控制备，检测限可降低1~2个数量级，达到10 ppb，并有效提高了颗粒复合层的稳定性，拓宽了纳米分散体的应用范围。